- Email: [email protected]
Large electrostrictive effect in Mn-doped BCZT ferroelectric ceramics
Ceramics International 45 (2019) 21315–21320
Contents lists available at ScienceDirect
Ceramics International journal homepage: www.elsevier.com/locate/ceramint
Large electrostrictive effect in Mn-doped BCZT ferroelectric ceramics a,∗
b,∗∗
Fan Feng , Yan Yan a b
T
Shaanxi Xueqian Normal University, Xi'an, 710100, China School of Materials and Energy, Southwest University, Chongqing, 400715, China
ARTICLE INFO
ABSTRACT
Keywords: Electrostrictive Lead-free Ferroelectric Ceramics
The electric field in ferroelectric ceramics can induce notable deformations or strains based mainly on the electrostrictive effect if the driving field is sufficiently large (normally larger than the coercive field). Therefore, a large electrostrictive effect is highly desired to achieve a high strain output. In the present work, 0.5Ba (Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT50) ferroelectric ceramics doped with different numbers of Mn ions were synthesized and their dielectric and ferroelectric properties were studied to comprehensively evaluate the electrostrictive effect in this system. The doping levels were set as 0.0025, 0.005, 0.01, and 0.02. It was found that Mn ions could lower the temperature corresponding to the maximum permittivity, Tm, drastically and induce diffuse phase-transition behaviors simultaneously. Most importantly, a purely electrostrictive effect with a longitudinal electrostrictive coefficient, Q33, as large as 0.0466 m4/C2 was observed between 22 and 80 °C. The Q33 of Mn-doped BCZT50 ceramics is much higher than some representative lead-based and lead-free ferroelectric ceramics. In this paper, a potential lead-free ferroelectric system with a large electrostrictive effect, which has potential applications in electrostrictive actuators, is reported.
1. Introduction The electrostrictive effect in ferroelectric ceramics has gained considerable attention over the last decade, since the strains induced by the electrostrictive effect have very small hysteresis and can be used in highresolution actuator devices [1,2]. Compared to the case of piezoelectric ceramics, such as Pb(Zr1-xTix)O3 (PZT), strong hysteresis has often been observed in strain-response curves of ferroelectric ceramics owing to the motion of domain walls [3,4]. This hysteresis affects the actuating performance significantly. In contrast, piezoelectric ceramics need a pre-poling process prior to usage; therefore the production cost of piezoelectric ceramics increases and the production rate decreases [5–10]. According to the theory of thermodynamics, the electrostrictive effect describes a secondorder effect between the input electric field/polarization and output strain. Such an effect exists in all dielectric materials, regardless of the material symmetry. The electrostrictive effect is frequently expressed by Eq. (1),
S3 = Q33 P32,
(1)
where S3, Q33, and P3 are the strain response, electrostrictive coefficient, and polarization, respectively. It should be pointed out that the piezoelectric and electrostrictive effects coexist in piezoelectric ceramics in the ferroelectric phase. Thus, the interference in the strain-response curves by the
∗
motion of the domain walls cannot be eliminated. Therefore, the Curie temperature (TC) of ferroelectric ceramics should be below room temperature to obtain purely electrostrictive strain. Pb(Mg1/3Nb2/3)O3 (PMN) is the first representative ferroelectric ceramic, which showed a notable electrostrictive characteristic with a Q33 of approximately 0.023 m4/C2 [11]. However, the use of lead is severely limited by European Parliament and in other countries [12–22]. In addition to the research upsurge of lead-free piezoelectric ceramics, the search for large electrostrictive effects in lead-free ferroelectric ceramics has attracted considerable attention. For example, electrostrictive properties have been reported in Bi0.5Na0.5TiO3 (BNT)-based ferroelectric ceramics. Q33 in this system is typically between approximately 0.02 m4/C2 and 0.03 m4/C2 [23–28], which is close to that of lead-containing PMN. Higher values have since been reported in 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT50) [29,30] and NaNbO3-xBaTiO3 (NN-xBT) [31–33] ferroelectric ceramics, with a Q33 of approximately 0.04 m4/C2. However, in BCZT50, the pure electrostrictive effect and anhysteretic strains were only detected above 100 °C, since the TC of BCZT50 is approximately 96 °C. From the point of view of application, the TC of BCZT50 should be shifted to approximately room temperature, and the electrostrictive effect should be maintained. Since the ferroelectricity in BCZT50 is mainly attributed to the B-site ion displacement [34], a disruption in the B-site long-range order effectively
Corresponding author. Corresponding author. E-mail addresses: [email protected] (F. Feng), [email protected] (Y. Yan).
∗∗
https://doi.org/10.1016/j.ceramint.2019.07.115 Received 28 June 2019; Received in revised form 9 July 2019; Accepted 9 July 2019 Available online 10 July 2019 0272-8842/ © 2019 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Ceramics International 45 (2019) 21315–21320
F. Feng and Y. Yan
Fig. 1. Room temperature XRD patterns of Mn-doped BCZT50 ceramics measured from 20° to 60° with a scanning step of 0.02°.
lowers TC, epically through an aliovalent doping strategy. In this study, we introduced Mn into BCZT50 to break the long-range order of BCZT, and successfully lowered the TC below room temperature with a minimal amount of 0.25%. A Q33 value of 0.0466 m4/C2 with an anhysteretic characteristic and high thermal stability is observed in Mn-doped BCZT50. This work proves that Mn-dopant can be considered as an effective doping element to tailor the dielectric and electrostrictive properties of BCZT50, and has potential applications in high-resolution actuators. 2. Experimental methods Mn-doped BCZT50 ceramics with x = 0.0025, 0.005, 0.01, and 0.02 were fabricated by a solid-state process, and Mn ions were assumed to replace B-site (Zr,Ti) ions. Raw materials of CaCO3, BaCO3, TiO2, ZrO2, and MnO2 produced by Aladdin Reagent (Shanghai, China) were weighted in stoichiometric amounts and then mixed for 6 h using a ball milling technique. After calcination at 1250 °C for 4 h, the powders were milled again for 12 h. A 5-wt.% polyvinyl acetate (PVA) binder was doped into the powders, which were then uniaxially pressed to form thin disks of 10 mm in diameter and 1.5 mm in height. The ceramics disks were sintered at 1450 °C for 4 h. Ground powders of Mn-doped BCZT50 were used to reveal the crystalline structures by X-ray diffraction (XRD, D/Max-IIIC, Rigaku, Japan) analysis in a θ-2θ scanning mode from 20° to 60°. The scanning step was set as 0.02°. Scanning electron microscopy (SEM, Quanta FEG 250, FEI, Hillsboro, USA) was used to reveal the grain morphologies. The surfaces of Mn-doped BCZT50 ceramics were polished by silica papers with different particle sizes, and then thermally etched at 1300 °C for 30 min. For dielectric and electrostrictive characterizations, silver paste was coated on the main surfaces and the discs were then sintered at 600 °C for 30 min. The temperature-dependent dielectric constants (εr) from 120 to 420 K were measured by a multi-frequency LCR meter (E4980A, Agilent, Palo Alto, U.S.) with a heating rate of 2 K/ min. Polarization-electric field (P-E) and strain-electric field (S-E) curves were generated simultaneously by a ferroelectric testing station (TF analyzer 2000, aixACCT, Aachen, Germany) combined with a photonic displacement sensor (MTI-2000, MTI Instruments, Washington, U.S.) at a measuring frequency of 0.1 Hz. Using the P-E and S-E curves, we plotted the S–P curves and calculated Q33 based on the fitting curves suggested by Eq. (1). 3. Results and discussion The XRD patterns of Mn-doped BCZT50 ceramics determined at room temperature are shown in Fig. 1. The diffraction peaks
Fig. 2. SEM microphotos on thermally etched surfaces of Mn-doped BCZT50 ceramics. (a) x = 0.0025; (b) x = 0.005; (c) x = 0.01 and (d) x = 0.02.
corresponding only to a pseudo-cubic symmetry are indexed from 20° to 60° within the resolution of XRD scanning. The missing peak splitting for the (200) group indicates that no non-cubic distortions exist in Mndoped BCZT50. A similar pseudo-cubic symmetry was identified in Fedoped BCZT50 ceramics [29]. The XRD patterns suggest that the TC of Mn-doped BCZT50 ceramics is shifted close to or below room temperature by doping Mn ions into the crystalline lattices, even though the lowest doping concentration is as low as 0.0025%. Fig. 2 shows the thermally etched surfaces of Mn-doped BCT-0.5BCT ceramics. The SEM micrographs reveal polygonal grains with few pores, suggesting compact structures. The grain size is roughly estimated as
21316
Ceramics International 45 (2019) 21315–21320
F. Feng and Y. Yan
Fig. 3. Dielectric constant as a function of temperature for undoped and Mndoped BCZT50 ceramics measured at 1 kHz, 10 kHz, and 100 kHz from 120 K to 420 K at a heating rate of 2 K/min. (a) x = 0; (b) x = 0.0025; (c) x = 0.005; (d) x = 0.01 and (e) x = 0.02. (f) Dielectric constant measured at 100 kHz as a function of temperature for undoped and Mn-doped BCZT50 ceramics. The inset of Fig. 3(f) shows the Tm as a function of doping content.
Fig. 4. (a) εr/εm versus T-Tm curves for undoped and Mn-doped BCZT50 ceramics measured at 100 kHz. (b) The W2/3M − H and δg as a function of doping content. The insets of Fig. 4(b) show the fitting results based on Eq. (3).
approximately 2–3 μm. Compared to the case of pristine BCZT ceramics sintered under the sample conditions, the grain size decreased drastically from dozens of microns to several microns. It is assumed that introducing Mn ions into BCZT50 results in the generation of oxygen vaccines, which might reduce the mobility of grain boundaries during sintering, consequently inhibiting the grain growth. This phenomenon was observed in several acceptor-doped lead-containing ferrielectric ceramics [35,36]. Fig. 3 shows the dielectric constants of Mn-doped BCZT50 ceramics, determined at 1, 10, and 100 kHz from 120 to 420 K. The dielectric properties of undoped BCZT50 are included for comparison. The TC of undoped BCZT50 is 365 K, as indicated by the sharp peak in dielectric constant, which is consistent with previous observations [30,37]. In the low-temperature region, there is a dielectric step at approximately 300 K, which is attributed to a tetragonal-to-rhombohedral phase transition [34]. In contrast, in Mn-doped BCZT50 ceramics, the sharp ferroelectric-to-paraelectric phase-transition peaks become broad diffuse phase-transition (DPT) peaks when the Mn ions increase from 0.0025 to 0.02, as shown in Fig. 3(b)–(e). Since Mn-doped BCZT50 ceramics exhibit DPT features, it is convenient to use the term Tm instead of TC to denote the temperature correlated to the maximum εr. εr shows little difference on the low-temperature side, because it converts
to the same value as the temperature is a few degrees above the Tm. Fig. 3(f) shows the dielectric constant (measured at 100 kHz) of undoped and Mn-doped BCZT50 samples as a function of temperature. It is clear that Tm decreased drastically with the introduction of the Mn ions into the BCZT system, from 360 K in x = 0 to approximately 280 K in x = 0.02. It is interesting to note that either Fe or Mn ions are frequently used as acceptor-dopants to tailor the dielectric and proprieties in lead-containing ceramics, such as PZT [2,4,35]. However, the TC of these acceptor-doped PZT ceramics is reduced by a few K. This phenomenon suggests that the ferroelectricity of lead-containing systems is considerably stronger than these of lead-free systems. With the introduction of Mn ions into the BCZT50 system, the dielectric properties of doped compositions exhibit the same typical DPT characteristics, such as broadening of the phase-transition peaks. We adopt two methods to describe the DPT width (or the degree of diffuseness) quantitively. According to Fig. 4(a), W2/3M − H and W2/3M-L are defined as the difference between Tm and the temperatures correspond to εr, which reaches two-thirds of the maximum value on the high-temperature and low-temperature sides of the dielectric peaks, respectively. Here, W2/3M − H is used to evaluate the DPT width, because the second method can only extract the diffuseness from the high-temperature side. Fig. 4(b) shows the DPT width as a function of x
21317
Ceramics International 45 (2019) 21315–21320
F. Feng and Y. Yan
Fig. 5. P-E hysteresis loops (group 1) and corresponding S-E curves (group 2) of Mn-doped BCZT50 ceramics measured at different temperature. (a) x = 0.0025; (b) x = 0.005; (c) x = 0.01 and (d) x = 0.02.
represented by W2/3M-H. The DPT width of undoped BCZT50 is only approximately 20 K. In contrast, the DPT width in Mn-doped BCZT50 increased abruptly from 45 to 50 K. This value is as much as twice that of the undoped counterpart. The DPT width was also calculated based on the diffuseness parameter (δg) [38]. It was supposed that the DPT width was attributed to a Gaussian distribution of TC. Thus, εm can be expressed as a function of temperature by Eq. (2), m
=
r exp
TC ) 2
(T 2
2 g
,
(2)
where, εm is the maximum εr, and δg the Gaussian diffuseness. Eq. (2) was expanded as power series, and all higher orders were omitted. Then, we obtained Eq. (3) to extract δg with a limitation of 1 < εm/ εr < 1.5. m r
=1+
1 (T TC )2 2 2 g2
(3)
Eq. (3) is similar to the Curie-Weiss law, and can be used to calculate the dielectric properties above the TC of ferroelectric materials. Representative fitting results for x = 0 and x = 0.005 are shown in the insets of Fig. 4(b). It is evident that the εr of these two samples above TC can be described well by Eq. (3), which suggests the effectiveness of this method. The Gaussian δg as a function of doping content is illustrated in Fig. 4(b). Note that the DPT widths extracted by the two aforementioned methods yield very similar values. These results confirm that the diffuseness degree of BCZT50 ceramics is drastically increased by Mn ions, even though the doping level is as low as 0.0025. Owing to the appearance of such a DPT, anhysteretic S–P curves are expected in these Mn-doped BCZT50 ceramics. To determine the electrostrictive coefficient, we need to obtain both P-E and S-E curves of Mn-doped BCZT50 ceramics. Fig. 5 presents the PE and S-E curves of Mn-doped BCZT50 ceramics determined at 22, 40, 60 and 80 °C. Note that in the x = 0.0025 composition, the maximum electric field (Emax) was set as 30 kV/cm, whereas Emax was 40 kV/cm for other three compositions. Both P-E and S-E curves of Mn-doped BCZT50 ceramics show very slim characteristics, which suggest that electrostrictive effect, instead of extrinsic domain wall motion, dominate the strain responses. Although the strain levels show a variation regarding to the x content, the purely electrostrictive nature of the
strain responses can be identified according to Fig. 5. Representative S–P curves measured at 22, 40, 60, and 80 °C for BCZT50 ceramics doped with different Mn ion concentrations are shown in Fig. 6. Fig. 6 illustrates that for all studied compositions, both the polarization and induced strain decrease as temperature increases. More importantly, all S–P curves are well fitted by the quadratic relation expressed in Eq. (1). In undoped BCZT ceramics, there are large differences between the measured S–P curves and fitting curves, especially in the low electric-field regions, which is attributed to the domain-wall motion [25,39,40]. In contrast to the S–P behaviors in undoped BCZT50 ceramics, the S–P behaviors of Mn-doped BCZT50 ceramics follow the quadratic relation strictly, suggesting a purely electrostrictive response. The corresponding P-E loops and S-E curves of these studied compositions are rather slim. Fig. 7(a) shows Q33 for Mndoped BCZT50 ceramics as a function of temperature. The maximum/ minimum ratios of Q33 for these compositions are 1.049, 1.021, 1.093, and 1.021, respectively. Taking into account discrepancies during measurement, it can be seen that Q33 is almost insensitive to temperature. Although the temperature region center is at Tm, εr changes considerably as a result of the phase transition. In contrast, Q33 does not change evidently. The thermal stability of Q33 has also been reported in many ferroelectric ceramics, including BNT-based and BT-based systems [25–28,41–49]. An average Q33 value of 0.0466 m4/C2 for the studied compositions is obtained for the Mn-doped BCZT50 ceramics. As summarized in Fig. 7(b), the Q33 of lead-containing and BNT-based ferroelectric materials is normally less than 0.03 m4/C2. The Q33 of Mndoped BCZT50 is impressive, and almost twice that in these systems. For example, in the (Sr0.35Na0.25Bi0.35)TiO3 ceramic, although a purely electrostrictive response was observed, Q33 was merely 0.02 m4/C2 [23]. In contrast, although Q33 values of approximately 0.021–0.027 were reported for other lead-free ferroelectric ceramics, inherent hysteresis in S–P curves were also observed in these ferroelectric or antiferroelectric ceramics owing to domain-walls movement [24]. A purely electrostrictive response with a high Q33 was obtained simultaneously only in Mn-doped BCZT50 ceramics. This feature makes Mn-doped BCZT50 ceramics a potential candidate for applications in high-resolution actuator devices. 4. Conclusions
21318
In summary, the doping effects of Mn ions on the dielectric and
Ceramics International 45 (2019) 21315–21320
F. Feng and Y. Yan
Fig. 6. Representative S–P curves for Mn-doped BCZT50 ceramics measured at 22 °C, 40 °C, 60 °C and 80 °C. (a) x = 0.0025; (b) x = 0.005; (c) x = 0.01 and (d) x = 0.02. Open circles are measuring data and solid lines are fitting curves based on Eq. (1). Fig. 7. (a) Q33 as a function of temperature for Mndoped BCZT50 ceramics. (b) Comparison of the Q33 among representative ferroelectric ceramics and single crystals, including PMN [11], PMN crystal [50], PZN crystal [50], 0.82(0.94BNT-0.06BT)-0.18KNN [24], 0.93BNT-0.07BT [24], (Sr0.35Na0.25Bi0.35)TiO3 (SNBT) [23], 0.9(Bi0.5Na0.5)TiO3-0.08KNbO30.02SrTiO3 (0.90BNT-0.08KN-0.02ST) [27], 0.74BNT0.06BT-0.2KNN [51], 0.95Bi1/2(Na0.82K0.18)1/2TiO30.05BaZrO3 (0.95BNKT-0.05BZ) [49], (Na0.42Bi0.48) Ti0.93O2.79-0.07 BaTiO3 (0.93NBT-0.07BT) [52], 0.095Bi0.5(Na0.78K0.22)0.5TiO3-0.05Bi(Ni0.5Ti0.5)O3 (BNKT-0.05BNT) [53], BCZT50 [30], NN-0.25BT [33] and this work. PZN: Pb(Zr1/3Nb2/3)O3; KNN: (K0.5Na0.5) NbO3, KN: KNbO3.
electrostrictive properties of BCZT50 ceramics were investigated by means of dielectric spectrum and S–P curves. Besides the decreases in grain size and Tm and the notable DPT characteristic, a purely electrostrictive response (anhysteretic in S–P curves), high Q33 (average of 0.0466 m4/C2), and high temperature stability (from 22 °C to 80 °C) were observed in this system. These merits suggest that Mn-doped BCZT50 ceramics can be considered as promising electrostrictive materials in actuators. Acknowledgements The work is supported by the Fundamental Research Funds for the Central Universities (XDJK2018B009 and XDJK2018C002). References [1] D. Damjanovic, Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics, Rep. Prog. Phys. 61 (1998) 1267–1324. [2] F. Li, L. Wang, L. Jin, D. Lin, J. Li, Z. Li, Z. Xu, S. Zhang, Piezoelectric activity in perovskite ferroelectric crystals, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 62 (2015) 18–32. [3] L. Jin, V. Porokhonskyy, D. Damjanovic, Domain wall contributions in Pb(Zr,Ti)O3 ceramics at morphotropic phase boundary: a study of dielectric dispersion, Appl.
Phys. Lett. 96 (2010) 242902. [4] L. Jin, Z. He, D. Damjanovic, Nanodomains in Fe+3-doped lead zirconate titanate ceramics at the morphotropic phase boundary do not correlate with high properties, Appl. Phys. Lett. 95 (2009) 012905. [5] F. Li, L. Jin, Z. Xu, S. Zhang, Electrostrictive effect in ferroelectrics: an alternative approach to improve piezoelectricity, Appl. Phys. Rev. 1 (2014) 011103. [6] L. Jin, F. Li, S. Zhang, Decoding the fingerprint of ferroelectric loops: comprehension of the material properties and structures, J. Am. Ceram. Soc. 97 (2014) 1–27. [7] K. Xu, J. Li, X. Lv, J.G. Wu, X.X. Zhang, D.Q. Xiao, J.G. Zhu, Superior piezoelectric properties in potassium-sodium niobate lead-free ceramics, Adv. Mater. 28 (2016) 8519–8523. [8] X. Wang, J. Wu, D. Xiao, J. Zhu, X. Cheng, T. Zheng, B. Zhang, X. Lou, X. Wang, Giant piezoelectricity in potassium-sodium niobate lead-free ceramics, J. Am. Ceram. Soc. 136 (2014) 2905–2910. [9] H. Zhang, C. Groh, Q. Zhang, W. Jo, K.G. Webber, J. Rödel, Large strain in relaxor/ ferroelectric composite lead-free piezoceramics, Adv. Electron. Mater. 1 (2015) 1500018. [10] H. Zhang, P. Xu, E. Patterson, J. Zang, S. Jiang, J. Rödel, Preparation and enhanced electrical properties of grain-oriented (Bi1/2Na1/2)TiO3-based lead-free incipient piezoceramics, J. Eur. Ceram. Soc. 35 (2015) 2501–2512. [11] J. Kuwata, K. Uchino, S. Nomura, Electrostrictive coefficients of Pb(Mg1/3Nb2/3)O3 ceramics, Jpn. J. Appl. Phys. 19 (1980) 2099–2103. [12] D. Damjanovic, N. Klein, J. Li, V. Porokhonskyy, What can be expected from leadfree piezoelectric materials? Funct. Mater. Lett. 3 (2010) 5–13. [13] J. Wu, D. Xiao, J. Zhu, Potassium-sodium niobate lead-free piezoelectric materials: past, present, and future of phase boundaries, Chem. Rev. 115 (2015) 2559–2595. [14] X. Wei, Y. Feng, L. Hang, S. Xia, L. Jin, X. Yao, Abnormal C–V curve and clockwise hysteresis loop in ferroelectric barium stannate titanate ceramics, Mater. Sci. Eng. B
21319
Ceramics International 45 (2019) 21315–21320
F. Feng and Y. Yan 120 (2005) 64–67. [15] L. Zhang, Y. Pu, M. Chen, Influence of BaZrO3 additive on the energy-storage properties of 0.775Na0.5Bi0.5TiO3-0.225BaSnO3 relaxor ferroelectrics, J. Alloy. Comp. 775 (2019) 342–347. [16] Y. Pu, L. Zhang, Y. Cui, M. Chen, High energy storage density and optical transparency of microwave sintered homogeneous (Na0.5Bi0.5)(1-x)BaxTi(1-y)SnyO3 ceramics, ACS Sustain. Chem. Eng. 6 (2018) 6102–6109. [17] Y. Pu, M. Yao, H. Liu, T. Frömling, Phase transition behavior, dielectric and ferroelectric properties of (1−x)(Bi0.5Na0.5)TiO3-xBa0.85Ca0.15Ti0.9Zr0.1O3 ceramics, J. Eur. Ceram. Soc. 36 (2016) 2461–2468. [18] Y. Pu, M. Yao, L. Zhang, P. Jing, High energy storage density of 0.55Bi0.5Na0.5TiO30.45Ba0.85Ca0.15Ti0.9-xZr0.1SnxO3 ceramics, J. Alloy. Comp. 687 (2016) 689–695. [19] W. Wang, Y. Pu, X. Guo, T. Ouyang, Y. Shi, M. Yang, J. Li, R. Shi, G. Liu, Enhanced energy storage properties of lead-free (Ca0.5Sr0.5)1-1.5xLaxTiO3 linear dielectric ceramics within a wide temperature range, Ceram. Int. 45 (2019) 14684–14690. [20] G. Liu, Y. Li, Z. Wang, L. Zhang, P. Chen, F. Wei, Y. Wang, K. Yu, Y. Yan, L. Jin, Z. He, Dielectric, ferroelectric and energy storage properties of lead-free (1-x) Ba0.9Sr0.1TiO3-xBi(Zn0.5Zr0.5)O3 ferroelectric ceramics sintered at lower temperature, Ceram. Int. 45 (2019) 15556–15565. [21] K. Han, N. Luo, Y. Jing, X. Wang, B. Peng, L. Liu, C. Hu, H. Zhou, Y. Wei, X. Chen, Q. Feng, Structure and energy storage performance of Ba-modified AgNbO3 leadfree antiferroelectric ceramics, Ceram. Int. 45 (2019) 5559–5565. [22] Z. Yang, F. Gao, H. Du, L. Jin, L. Yan, Q. Hu, Y. Yu, S. Qu, X. Wei, Z. Xu, Y.-J. Wang, Grain size engineered lead-free ceramics with both large energy storage density and ultrahigh mechanical properties, Nano Energy 58 (2019) 768–777. [23] C. Ang, Z. Yu, High, purely electrostrictive strain in lead-free dielectrics, Adv. Mater. 18 (2006) 103–106. [24] S.-T. Zhang, A.B. Kounga, W. Jo, C. Jamin, K. Seifert, T. Granzow, J. Rödel, D. Damjanovic, High-strain lead-free antiferroelectric electrostrictors, Adv. Mater. 21 (2009) 4716–4720. [25] L. Jin, W. Luo, L. Wang, Y. Tian, Q. Hu, L. Hou, L. Zhang, X. Lu, H. Du, X. Wei, G. Liu, Y. Yan, High thermal stability of electric field-induced strain in (1−x) (Bi0.5Na0.5)TiO3-xBa0.85Ca0.15Ti0.9Zr0.1O3 lead-free ferroelectrics, J. Eur. Ceram. Soc. 39 (2019) 277–286. [26] W. Bai, D. Chen, P. Zheng, J. Zhang, B. Shen, J. Zhai, Z. Ji, Grain-orientated leadfree BNT-based piezoceramics with giant electrostrictive effect, Ceram. Int. 43 (2017) 3339–3345. [27] W. Bai, L. Li, W. Wang, B. Shen, J. Zhai, Phase diagram and electrostrictive effect in BNT-based ceramics, Solid State Commun. 206 (2015) 22–25. [28] J. Hao, W. Bai, W. Li, B. Shen, J. Zhai, Phase transitions, relaxor behavior, and electrical properties in (1-x)(Bi0.5Na0.5)TiO3-x(K0.5Na0.5)NbO3 lead-free piezoceramics, J. Mater. Res. 27 (2012) 2943–2955. [29] L. Jin, R. Huo, R. Guo, F. Li, D. Wang, Y. Tian, Q. Hu, X. Wei, Z. He, Y. Yan, G. Liu, Diffuse phase transitions and giant electrostrictive coefficients in lead-free Fe3+doped 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ferroelectric ceramics, ACS Appl. Mater. Interfaces 8 (2016) 31109–31119. [30] F. Li, L. Jin, R. Guo, High electrostrictive coefficient Q33 in lead-free Ba(Zr0.2Ti0.8) O3-x(Ba0.7Ca0.3)TiO3 piezoelectric ceramics, Appl. Phys. Lett. 105 (2014) 232903. [31] R. Zuo, H. Qi, J. Fu, J. Li, M. Shi, Y. Xu, Giant electrostrictive effects of NaNbO3BaTiO3 lead-free relaxor ferroelectrics, Appl. Phys. Lett. 108 (2016) 232904. [32] X. Lu, L. Hou, L. Jin, L. Wang, Y. Tian, K. Yu, Q. Hu, L. Zhang, X. Wei, Structure evolution and exceptionally ultra-low hysteresis unipolar electric field-induced strain in (1−x)NaNbO3-xBaTiO3 lead-free ferroelectrics, Ceram. Int. 44 (2018) 5492–5499. [33] X. Lu, L. Hou, L. Jin, D. Wang, Q. Hu, D.O. Alikin, A.P. Turygin, L. Wang, L. Zhang, X. Wei, Origin of composition-insensitive electrostrictive coefficient and continuous decrease of domain wall density in (1−x)NaNbO3-xBaTiO3 lead-free ferroelectrics, J. Eur. Ceram. Soc. 38 (2018) 3127–3135.
[34] W. Liu, X. Ren, Large piezoelectric effect in Pb-free ceramics, Phys. Rev. Lett. 103 (2009) 257602. [35] L. Jin, D. Damjanovic Porokhonskyy, Separation of piezoelectric grain resonance and domain wall dispersion in Pb(Zr,Ti)O3 ceramics, Appl. Phys. Lett. 94 (2009) 212906. [36] Z. Xing, L. Jin, T. Wang, Q. Hu, Y. Feng, X. Wei, Achieving both high d33 and high Qm for the Pb(Zr0.26Sn0.26Ti0.48)1-xFexO3-x/2 ternary system for use in high-power ultrasonic transducers, J. Electron. Mater. 43 (2014) 3905–3911. [37] P. Hansen, D. Hennings, H. Schreinemacher, Dielectric properties of acceptor-doped (Ba,Ca)(Ti,Zr)O3 ceramics, J. Electroceram. 2 (1998) 85–94. [38] K. Uchino, S. Nomura, Critical exponents of the dielectric constants in diffusedphase-transition crystals, Ferroelectrics 44 (1982) 55–61. [39] M.C. Ehmke, J. Glaum, M. Hoffman, J.E. Blendell, K.J. Bowman, The effect of electric poling on the performance of lead-free (1−x)Ba(Zr0.2Ti0.8)O3-x (Ba0.7Ca0.3)TiO3 piezoceramics, J. Am. Ceram. Soc. 96 (2013) 3805–3811. [40] Y. Tian, X. Chao, L. Jin, L. Wei, P. Liang, Z. Yang, Polymorphic structure evolution and large piezoelectric response of lead-free (Ba,Ca)(Zr,Ti)O3 ceramics, Appl. Phys. Lett. 104 (2014) 112901. [41] L. Jin, J. Qiao, L. Hou, L. Wang, L. Zhang, X. Lu, H. Du, X. Wei, Y. Yan, G. Liu, High electrostrictive effect in La3+-doped Ba(Zr0.2Ti0.8)O3 lead-free ferroelectrics, J. Alloy. Comp. 776 (2019) 599–605. [42] L. Jin, W. Luo, L. Hou, Y. Tian, Q. Hu, L. Wang, L. Zhang, X. Lu, H. Du, X. Wei, Y. Yan, G. Liu, High electric field-induced strain with ultra-low hysteresis and giant electrostrictive coefficient in barium strontium titanate lead-free ferroelectrics, J. Eur. Ceram. Soc. 39 (2019) 295–304. [43] H. Pan, J. Zhang, X. Jia, H. Xing, J. He, J. Wang, F. Wen, Large electrostrictive effect and high optical temperature sensing in Bi0.5Na0.5TiO3-BaTiO3(Sr0.7Bi0.18Er0.02)TiO3 luminescent ferroelectrics, Ceram. Int. 44 (2018) 5785–5789. [44] J. Hao, Z. Xu, R. Chu, W. Li, P. Fu, J. Du, G. Li, Structure evolution and electrostrictive properties in (Bi0.5Na0.5)0.94Ba0.06TiO3–M2O5 (M=Nb, Ta, Sb) lead-free piezoceramics, J. Eur. Ceram. Soc. 36 (2016) 4003–4014. [45] L. Jin, J. Qiao, L. Wang, L. Hou, R. Jing, J. Pang, L. Zhang, X. Lu, X. Wei, G. Liu, Y. Yan, Ultra-low hysteresis electric field-induced strain with high electrostrictive coefficient in lead-free Ba(ZrxTi1-x)O3 ferroelectrics, J. Alloy. Comp. 784 (2019) 931–938. [46] J. Hao, W. Li, J. Zhai, H. Chen, Progress in high-strain perovskite piezoelectric ceramics, Mater. Sci. Eng. R 135 (2019) 1–57. [47] L. Jin, J. Qiao, L. Hou, Y. Tian, Q. Hu, L. Wang, X. Lu, L. Zhang, H. Du, X. Wei, G. Liu, Y. Yan, A strategy for obtaining high electrostrictive properties and its application in barium stannate titanate lead-free ferroelectrics, Ceram. Int. 44 (2018) 21816–21824. [48] J. Hao, Z. Xu, R. Chu, W. Li, J. Du, Lead-free electrostrictive (Bi0.5Na0.5)TiO3(Bi0.5K0.5)TiO3-(K0.5Na0.5)NbO3 ceramics with good thermostability and fatiguefree behavior, J. Mater. Sci. 50 (2015) 5328–5336. [49] T. Vu Diem Ngoc, D. Thi Hinh, H.-S. Han, W. Jo, J.-S. Lee, Lead-free Bi1/ 2(Na0.82K0.18)1/2TiO3 relaxor ferroelectrics with temperature insensitive electrostrictive coefficient, Ceram. Int. 39 (2013) S119–S124. [50] K. Uchino, S. Nomura, L.E. Cross, S.J. Jang, R.E. Newnham, Electrostrictive effect in lead magnesium niobate single-crystals, J. Appl. Phys. 51 (1980) 1142–1145. [51] S.-T. Zhang, F. Yan, B. Yang, W. Cao, Phase diagram and electrostrictive properties of Bi0.5Na0.5TiO3–BaTiO3–K0.5Na0.5NbO3 ceramics, Appl. Phys. Lett. 97 (2010) 122901. [52] Y. Guo, M. Gu, H. Luo, Y. Liu, R.L. Withers, Composition-induced antiferroelectric phase and giant strain in lead-free (Nay,Biz)Ti1-xO3(1-x)-xBaTiO3 ceramics, Phys. Rev. B 83 (2011) 054118. [53] A. Ullah, H.B. Gul, A. Ullah, M. Sheeraz, J.-S. Bae, W. Jo, C.W. Ahn, I.W. Kim, T.H. Kim, Giant room-temperature electrostrictive coefficients in lead-free relaxor ferroelectric ceramics by compositional tuning, Apl. Mater. 6 (2018) 016104.
21320
Contents lists available at ScienceDirect
Ceramics International journal homepage: www.elsevier.com/locate/ceramint
Large electrostrictive effect in Mn-doped BCZT ferroelectric ceramics a,∗
b,∗∗
Fan Feng , Yan Yan a b
T
Shaanxi Xueqian Normal University, Xi'an, 710100, China School of Materials and Energy, Southwest University, Chongqing, 400715, China
ARTICLE INFO
ABSTRACT
Keywords: Electrostrictive Lead-free Ferroelectric Ceramics
The electric field in ferroelectric ceramics can induce notable deformations or strains based mainly on the electrostrictive effect if the driving field is sufficiently large (normally larger than the coercive field). Therefore, a large electrostrictive effect is highly desired to achieve a high strain output. In the present work, 0.5Ba (Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT50) ferroelectric ceramics doped with different numbers of Mn ions were synthesized and their dielectric and ferroelectric properties were studied to comprehensively evaluate the electrostrictive effect in this system. The doping levels were set as 0.0025, 0.005, 0.01, and 0.02. It was found that Mn ions could lower the temperature corresponding to the maximum permittivity, Tm, drastically and induce diffuse phase-transition behaviors simultaneously. Most importantly, a purely electrostrictive effect with a longitudinal electrostrictive coefficient, Q33, as large as 0.0466 m4/C2 was observed between 22 and 80 °C. The Q33 of Mn-doped BCZT50 ceramics is much higher than some representative lead-based and lead-free ferroelectric ceramics. In this paper, a potential lead-free ferroelectric system with a large electrostrictive effect, which has potential applications in electrostrictive actuators, is reported.
1. Introduction The electrostrictive effect in ferroelectric ceramics has gained considerable attention over the last decade, since the strains induced by the electrostrictive effect have very small hysteresis and can be used in highresolution actuator devices [1,2]. Compared to the case of piezoelectric ceramics, such as Pb(Zr1-xTix)O3 (PZT), strong hysteresis has often been observed in strain-response curves of ferroelectric ceramics owing to the motion of domain walls [3,4]. This hysteresis affects the actuating performance significantly. In contrast, piezoelectric ceramics need a pre-poling process prior to usage; therefore the production cost of piezoelectric ceramics increases and the production rate decreases [5–10]. According to the theory of thermodynamics, the electrostrictive effect describes a secondorder effect between the input electric field/polarization and output strain. Such an effect exists in all dielectric materials, regardless of the material symmetry. The electrostrictive effect is frequently expressed by Eq. (1),
S3 = Q33 P32,
(1)
where S3, Q33, and P3 are the strain response, electrostrictive coefficient, and polarization, respectively. It should be pointed out that the piezoelectric and electrostrictive effects coexist in piezoelectric ceramics in the ferroelectric phase. Thus, the interference in the strain-response curves by the
∗
motion of the domain walls cannot be eliminated. Therefore, the Curie temperature (TC) of ferroelectric ceramics should be below room temperature to obtain purely electrostrictive strain. Pb(Mg1/3Nb2/3)O3 (PMN) is the first representative ferroelectric ceramic, which showed a notable electrostrictive characteristic with a Q33 of approximately 0.023 m4/C2 [11]. However, the use of lead is severely limited by European Parliament and in other countries [12–22]. In addition to the research upsurge of lead-free piezoelectric ceramics, the search for large electrostrictive effects in lead-free ferroelectric ceramics has attracted considerable attention. For example, electrostrictive properties have been reported in Bi0.5Na0.5TiO3 (BNT)-based ferroelectric ceramics. Q33 in this system is typically between approximately 0.02 m4/C2 and 0.03 m4/C2 [23–28], which is close to that of lead-containing PMN. Higher values have since been reported in 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT50) [29,30] and NaNbO3-xBaTiO3 (NN-xBT) [31–33] ferroelectric ceramics, with a Q33 of approximately 0.04 m4/C2. However, in BCZT50, the pure electrostrictive effect and anhysteretic strains were only detected above 100 °C, since the TC of BCZT50 is approximately 96 °C. From the point of view of application, the TC of BCZT50 should be shifted to approximately room temperature, and the electrostrictive effect should be maintained. Since the ferroelectricity in BCZT50 is mainly attributed to the B-site ion displacement [34], a disruption in the B-site long-range order effectively
Corresponding author. Corresponding author. E-mail addresses: [email protected] (F. Feng), [email protected] (Y. Yan).
∗∗
https://doi.org/10.1016/j.ceramint.2019.07.115 Received 28 June 2019; Received in revised form 9 July 2019; Accepted 9 July 2019 Available online 10 July 2019 0272-8842/ © 2019 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Ceramics International 45 (2019) 21315–21320
F. Feng and Y. Yan
Fig. 1. Room temperature XRD patterns of Mn-doped BCZT50 ceramics measured from 20° to 60° with a scanning step of 0.02°.
lowers TC, epically through an aliovalent doping strategy. In this study, we introduced Mn into BCZT50 to break the long-range order of BCZT, and successfully lowered the TC below room temperature with a minimal amount of 0.25%. A Q33 value of 0.0466 m4/C2 with an anhysteretic characteristic and high thermal stability is observed in Mn-doped BCZT50. This work proves that Mn-dopant can be considered as an effective doping element to tailor the dielectric and electrostrictive properties of BCZT50, and has potential applications in high-resolution actuators. 2. Experimental methods Mn-doped BCZT50 ceramics with x = 0.0025, 0.005, 0.01, and 0.02 were fabricated by a solid-state process, and Mn ions were assumed to replace B-site (Zr,Ti) ions. Raw materials of CaCO3, BaCO3, TiO2, ZrO2, and MnO2 produced by Aladdin Reagent (Shanghai, China) were weighted in stoichiometric amounts and then mixed for 6 h using a ball milling technique. After calcination at 1250 °C for 4 h, the powders were milled again for 12 h. A 5-wt.% polyvinyl acetate (PVA) binder was doped into the powders, which were then uniaxially pressed to form thin disks of 10 mm in diameter and 1.5 mm in height. The ceramics disks were sintered at 1450 °C for 4 h. Ground powders of Mn-doped BCZT50 were used to reveal the crystalline structures by X-ray diffraction (XRD, D/Max-IIIC, Rigaku, Japan) analysis in a θ-2θ scanning mode from 20° to 60°. The scanning step was set as 0.02°. Scanning electron microscopy (SEM, Quanta FEG 250, FEI, Hillsboro, USA) was used to reveal the grain morphologies. The surfaces of Mn-doped BCZT50 ceramics were polished by silica papers with different particle sizes, and then thermally etched at 1300 °C for 30 min. For dielectric and electrostrictive characterizations, silver paste was coated on the main surfaces and the discs were then sintered at 600 °C for 30 min. The temperature-dependent dielectric constants (εr) from 120 to 420 K were measured by a multi-frequency LCR meter (E4980A, Agilent, Palo Alto, U.S.) with a heating rate of 2 K/ min. Polarization-electric field (P-E) and strain-electric field (S-E) curves were generated simultaneously by a ferroelectric testing station (TF analyzer 2000, aixACCT, Aachen, Germany) combined with a photonic displacement sensor (MTI-2000, MTI Instruments, Washington, U.S.) at a measuring frequency of 0.1 Hz. Using the P-E and S-E curves, we plotted the S–P curves and calculated Q33 based on the fitting curves suggested by Eq. (1). 3. Results and discussion The XRD patterns of Mn-doped BCZT50 ceramics determined at room temperature are shown in Fig. 1. The diffraction peaks
Fig. 2. SEM microphotos on thermally etched surfaces of Mn-doped BCZT50 ceramics. (a) x = 0.0025; (b) x = 0.005; (c) x = 0.01 and (d) x = 0.02.
corresponding only to a pseudo-cubic symmetry are indexed from 20° to 60° within the resolution of XRD scanning. The missing peak splitting for the (200) group indicates that no non-cubic distortions exist in Mndoped BCZT50. A similar pseudo-cubic symmetry was identified in Fedoped BCZT50 ceramics [29]. The XRD patterns suggest that the TC of Mn-doped BCZT50 ceramics is shifted close to or below room temperature by doping Mn ions into the crystalline lattices, even though the lowest doping concentration is as low as 0.0025%. Fig. 2 shows the thermally etched surfaces of Mn-doped BCT-0.5BCT ceramics. The SEM micrographs reveal polygonal grains with few pores, suggesting compact structures. The grain size is roughly estimated as
21316
Ceramics International 45 (2019) 21315–21320
F. Feng and Y. Yan
Fig. 3. Dielectric constant as a function of temperature for undoped and Mndoped BCZT50 ceramics measured at 1 kHz, 10 kHz, and 100 kHz from 120 K to 420 K at a heating rate of 2 K/min. (a) x = 0; (b) x = 0.0025; (c) x = 0.005; (d) x = 0.01 and (e) x = 0.02. (f) Dielectric constant measured at 100 kHz as a function of temperature for undoped and Mn-doped BCZT50 ceramics. The inset of Fig. 3(f) shows the Tm as a function of doping content.
Fig. 4. (a) εr/εm versus T-Tm curves for undoped and Mn-doped BCZT50 ceramics measured at 100 kHz. (b) The W2/3M − H and δg as a function of doping content. The insets of Fig. 4(b) show the fitting results based on Eq. (3).
approximately 2–3 μm. Compared to the case of pristine BCZT ceramics sintered under the sample conditions, the grain size decreased drastically from dozens of microns to several microns. It is assumed that introducing Mn ions into BCZT50 results in the generation of oxygen vaccines, which might reduce the mobility of grain boundaries during sintering, consequently inhibiting the grain growth. This phenomenon was observed in several acceptor-doped lead-containing ferrielectric ceramics [35,36]. Fig. 3 shows the dielectric constants of Mn-doped BCZT50 ceramics, determined at 1, 10, and 100 kHz from 120 to 420 K. The dielectric properties of undoped BCZT50 are included for comparison. The TC of undoped BCZT50 is 365 K, as indicated by the sharp peak in dielectric constant, which is consistent with previous observations [30,37]. In the low-temperature region, there is a dielectric step at approximately 300 K, which is attributed to a tetragonal-to-rhombohedral phase transition [34]. In contrast, in Mn-doped BCZT50 ceramics, the sharp ferroelectric-to-paraelectric phase-transition peaks become broad diffuse phase-transition (DPT) peaks when the Mn ions increase from 0.0025 to 0.02, as shown in Fig. 3(b)–(e). Since Mn-doped BCZT50 ceramics exhibit DPT features, it is convenient to use the term Tm instead of TC to denote the temperature correlated to the maximum εr. εr shows little difference on the low-temperature side, because it converts
to the same value as the temperature is a few degrees above the Tm. Fig. 3(f) shows the dielectric constant (measured at 100 kHz) of undoped and Mn-doped BCZT50 samples as a function of temperature. It is clear that Tm decreased drastically with the introduction of the Mn ions into the BCZT system, from 360 K in x = 0 to approximately 280 K in x = 0.02. It is interesting to note that either Fe or Mn ions are frequently used as acceptor-dopants to tailor the dielectric and proprieties in lead-containing ceramics, such as PZT [2,4,35]. However, the TC of these acceptor-doped PZT ceramics is reduced by a few K. This phenomenon suggests that the ferroelectricity of lead-containing systems is considerably stronger than these of lead-free systems. With the introduction of Mn ions into the BCZT50 system, the dielectric properties of doped compositions exhibit the same typical DPT characteristics, such as broadening of the phase-transition peaks. We adopt two methods to describe the DPT width (or the degree of diffuseness) quantitively. According to Fig. 4(a), W2/3M − H and W2/3M-L are defined as the difference between Tm and the temperatures correspond to εr, which reaches two-thirds of the maximum value on the high-temperature and low-temperature sides of the dielectric peaks, respectively. Here, W2/3M − H is used to evaluate the DPT width, because the second method can only extract the diffuseness from the high-temperature side. Fig. 4(b) shows the DPT width as a function of x
21317
Ceramics International 45 (2019) 21315–21320
F. Feng and Y. Yan
Fig. 5. P-E hysteresis loops (group 1) and corresponding S-E curves (group 2) of Mn-doped BCZT50 ceramics measured at different temperature. (a) x = 0.0025; (b) x = 0.005; (c) x = 0.01 and (d) x = 0.02.
represented by W2/3M-H. The DPT width of undoped BCZT50 is only approximately 20 K. In contrast, the DPT width in Mn-doped BCZT50 increased abruptly from 45 to 50 K. This value is as much as twice that of the undoped counterpart. The DPT width was also calculated based on the diffuseness parameter (δg) [38]. It was supposed that the DPT width was attributed to a Gaussian distribution of TC. Thus, εm can be expressed as a function of temperature by Eq. (2), m
=
r exp
TC ) 2
(T 2
2 g
,
(2)
where, εm is the maximum εr, and δg the Gaussian diffuseness. Eq. (2) was expanded as power series, and all higher orders were omitted. Then, we obtained Eq. (3) to extract δg with a limitation of 1 < εm/ εr < 1.5. m r
=1+
1 (T TC )2 2 2 g2
(3)
Eq. (3) is similar to the Curie-Weiss law, and can be used to calculate the dielectric properties above the TC of ferroelectric materials. Representative fitting results for x = 0 and x = 0.005 are shown in the insets of Fig. 4(b). It is evident that the εr of these two samples above TC can be described well by Eq. (3), which suggests the effectiveness of this method. The Gaussian δg as a function of doping content is illustrated in Fig. 4(b). Note that the DPT widths extracted by the two aforementioned methods yield very similar values. These results confirm that the diffuseness degree of BCZT50 ceramics is drastically increased by Mn ions, even though the doping level is as low as 0.0025. Owing to the appearance of such a DPT, anhysteretic S–P curves are expected in these Mn-doped BCZT50 ceramics. To determine the electrostrictive coefficient, we need to obtain both P-E and S-E curves of Mn-doped BCZT50 ceramics. Fig. 5 presents the PE and S-E curves of Mn-doped BCZT50 ceramics determined at 22, 40, 60 and 80 °C. Note that in the x = 0.0025 composition, the maximum electric field (Emax) was set as 30 kV/cm, whereas Emax was 40 kV/cm for other three compositions. Both P-E and S-E curves of Mn-doped BCZT50 ceramics show very slim characteristics, which suggest that electrostrictive effect, instead of extrinsic domain wall motion, dominate the strain responses. Although the strain levels show a variation regarding to the x content, the purely electrostrictive nature of the
strain responses can be identified according to Fig. 5. Representative S–P curves measured at 22, 40, 60, and 80 °C for BCZT50 ceramics doped with different Mn ion concentrations are shown in Fig. 6. Fig. 6 illustrates that for all studied compositions, both the polarization and induced strain decrease as temperature increases. More importantly, all S–P curves are well fitted by the quadratic relation expressed in Eq. (1). In undoped BCZT ceramics, there are large differences between the measured S–P curves and fitting curves, especially in the low electric-field regions, which is attributed to the domain-wall motion [25,39,40]. In contrast to the S–P behaviors in undoped BCZT50 ceramics, the S–P behaviors of Mn-doped BCZT50 ceramics follow the quadratic relation strictly, suggesting a purely electrostrictive response. The corresponding P-E loops and S-E curves of these studied compositions are rather slim. Fig. 7(a) shows Q33 for Mndoped BCZT50 ceramics as a function of temperature. The maximum/ minimum ratios of Q33 for these compositions are 1.049, 1.021, 1.093, and 1.021, respectively. Taking into account discrepancies during measurement, it can be seen that Q33 is almost insensitive to temperature. Although the temperature region center is at Tm, εr changes considerably as a result of the phase transition. In contrast, Q33 does not change evidently. The thermal stability of Q33 has also been reported in many ferroelectric ceramics, including BNT-based and BT-based systems [25–28,41–49]. An average Q33 value of 0.0466 m4/C2 for the studied compositions is obtained for the Mn-doped BCZT50 ceramics. As summarized in Fig. 7(b), the Q33 of lead-containing and BNT-based ferroelectric materials is normally less than 0.03 m4/C2. The Q33 of Mndoped BCZT50 is impressive, and almost twice that in these systems. For example, in the (Sr0.35Na0.25Bi0.35)TiO3 ceramic, although a purely electrostrictive response was observed, Q33 was merely 0.02 m4/C2 [23]. In contrast, although Q33 values of approximately 0.021–0.027 were reported for other lead-free ferroelectric ceramics, inherent hysteresis in S–P curves were also observed in these ferroelectric or antiferroelectric ceramics owing to domain-walls movement [24]. A purely electrostrictive response with a high Q33 was obtained simultaneously only in Mn-doped BCZT50 ceramics. This feature makes Mn-doped BCZT50 ceramics a potential candidate for applications in high-resolution actuator devices. 4. Conclusions
21318
In summary, the doping effects of Mn ions on the dielectric and
Ceramics International 45 (2019) 21315–21320
F. Feng and Y. Yan
Fig. 6. Representative S–P curves for Mn-doped BCZT50 ceramics measured at 22 °C, 40 °C, 60 °C and 80 °C. (a) x = 0.0025; (b) x = 0.005; (c) x = 0.01 and (d) x = 0.02. Open circles are measuring data and solid lines are fitting curves based on Eq. (1). Fig. 7. (a) Q33 as a function of temperature for Mndoped BCZT50 ceramics. (b) Comparison of the Q33 among representative ferroelectric ceramics and single crystals, including PMN [11], PMN crystal [50], PZN crystal [50], 0.82(0.94BNT-0.06BT)-0.18KNN [24], 0.93BNT-0.07BT [24], (Sr0.35Na0.25Bi0.35)TiO3 (SNBT) [23], 0.9(Bi0.5Na0.5)TiO3-0.08KNbO30.02SrTiO3 (0.90BNT-0.08KN-0.02ST) [27], 0.74BNT0.06BT-0.2KNN [51], 0.95Bi1/2(Na0.82K0.18)1/2TiO30.05BaZrO3 (0.95BNKT-0.05BZ) [49], (Na0.42Bi0.48) Ti0.93O2.79-0.07 BaTiO3 (0.93NBT-0.07BT) [52], 0.095Bi0.5(Na0.78K0.22)0.5TiO3-0.05Bi(Ni0.5Ti0.5)O3 (BNKT-0.05BNT) [53], BCZT50 [30], NN-0.25BT [33] and this work. PZN: Pb(Zr1/3Nb2/3)O3; KNN: (K0.5Na0.5) NbO3, KN: KNbO3.
electrostrictive properties of BCZT50 ceramics were investigated by means of dielectric spectrum and S–P curves. Besides the decreases in grain size and Tm and the notable DPT characteristic, a purely electrostrictive response (anhysteretic in S–P curves), high Q33 (average of 0.0466 m4/C2), and high temperature stability (from 22 °C to 80 °C) were observed in this system. These merits suggest that Mn-doped BCZT50 ceramics can be considered as promising electrostrictive materials in actuators. Acknowledgements The work is supported by the Fundamental Research Funds for the Central Universities (XDJK2018B009 and XDJK2018C002). References [1] D. Damjanovic, Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics, Rep. Prog. Phys. 61 (1998) 1267–1324. [2] F. Li, L. Wang, L. Jin, D. Lin, J. Li, Z. Li, Z. Xu, S. Zhang, Piezoelectric activity in perovskite ferroelectric crystals, IEEE Trans. Ultrason. Ferroelectr. Freq. Control 62 (2015) 18–32. [3] L. Jin, V. Porokhonskyy, D. Damjanovic, Domain wall contributions in Pb(Zr,Ti)O3 ceramics at morphotropic phase boundary: a study of dielectric dispersion, Appl.
Phys. Lett. 96 (2010) 242902. [4] L. Jin, Z. He, D. Damjanovic, Nanodomains in Fe+3-doped lead zirconate titanate ceramics at the morphotropic phase boundary do not correlate with high properties, Appl. Phys. Lett. 95 (2009) 012905. [5] F. Li, L. Jin, Z. Xu, S. Zhang, Electrostrictive effect in ferroelectrics: an alternative approach to improve piezoelectricity, Appl. Phys. Rev. 1 (2014) 011103. [6] L. Jin, F. Li, S. Zhang, Decoding the fingerprint of ferroelectric loops: comprehension of the material properties and structures, J. Am. Ceram. Soc. 97 (2014) 1–27. [7] K. Xu, J. Li, X. Lv, J.G. Wu, X.X. Zhang, D.Q. Xiao, J.G. Zhu, Superior piezoelectric properties in potassium-sodium niobate lead-free ceramics, Adv. Mater. 28 (2016) 8519–8523. [8] X. Wang, J. Wu, D. Xiao, J. Zhu, X. Cheng, T. Zheng, B. Zhang, X. Lou, X. Wang, Giant piezoelectricity in potassium-sodium niobate lead-free ceramics, J. Am. Ceram. Soc. 136 (2014) 2905–2910. [9] H. Zhang, C. Groh, Q. Zhang, W. Jo, K.G. Webber, J. Rödel, Large strain in relaxor/ ferroelectric composite lead-free piezoceramics, Adv. Electron. Mater. 1 (2015) 1500018. [10] H. Zhang, P. Xu, E. Patterson, J. Zang, S. Jiang, J. Rödel, Preparation and enhanced electrical properties of grain-oriented (Bi1/2Na1/2)TiO3-based lead-free incipient piezoceramics, J. Eur. Ceram. Soc. 35 (2015) 2501–2512. [11] J. Kuwata, K. Uchino, S. Nomura, Electrostrictive coefficients of Pb(Mg1/3Nb2/3)O3 ceramics, Jpn. J. Appl. Phys. 19 (1980) 2099–2103. [12] D. Damjanovic, N. Klein, J. Li, V. Porokhonskyy, What can be expected from leadfree piezoelectric materials? Funct. Mater. Lett. 3 (2010) 5–13. [13] J. Wu, D. Xiao, J. Zhu, Potassium-sodium niobate lead-free piezoelectric materials: past, present, and future of phase boundaries, Chem. Rev. 115 (2015) 2559–2595. [14] X. Wei, Y. Feng, L. Hang, S. Xia, L. Jin, X. Yao, Abnormal C–V curve and clockwise hysteresis loop in ferroelectric barium stannate titanate ceramics, Mater. Sci. Eng. B
21319
Ceramics International 45 (2019) 21315–21320
F. Feng and Y. Yan 120 (2005) 64–67. [15] L. Zhang, Y. Pu, M. Chen, Influence of BaZrO3 additive on the energy-storage properties of 0.775Na0.5Bi0.5TiO3-0.225BaSnO3 relaxor ferroelectrics, J. Alloy. Comp. 775 (2019) 342–347. [16] Y. Pu, L. Zhang, Y. Cui, M. Chen, High energy storage density and optical transparency of microwave sintered homogeneous (Na0.5Bi0.5)(1-x)BaxTi(1-y)SnyO3 ceramics, ACS Sustain. Chem. Eng. 6 (2018) 6102–6109. [17] Y. Pu, M. Yao, H. Liu, T. Frömling, Phase transition behavior, dielectric and ferroelectric properties of (1−x)(Bi0.5Na0.5)TiO3-xBa0.85Ca0.15Ti0.9Zr0.1O3 ceramics, J. Eur. Ceram. Soc. 36 (2016) 2461–2468. [18] Y. Pu, M. Yao, L. Zhang, P. Jing, High energy storage density of 0.55Bi0.5Na0.5TiO30.45Ba0.85Ca0.15Ti0.9-xZr0.1SnxO3 ceramics, J. Alloy. Comp. 687 (2016) 689–695. [19] W. Wang, Y. Pu, X. Guo, T. Ouyang, Y. Shi, M. Yang, J. Li, R. Shi, G. Liu, Enhanced energy storage properties of lead-free (Ca0.5Sr0.5)1-1.5xLaxTiO3 linear dielectric ceramics within a wide temperature range, Ceram. Int. 45 (2019) 14684–14690. [20] G. Liu, Y. Li, Z. Wang, L. Zhang, P. Chen, F. Wei, Y. Wang, K. Yu, Y. Yan, L. Jin, Z. He, Dielectric, ferroelectric and energy storage properties of lead-free (1-x) Ba0.9Sr0.1TiO3-xBi(Zn0.5Zr0.5)O3 ferroelectric ceramics sintered at lower temperature, Ceram. Int. 45 (2019) 15556–15565. [21] K. Han, N. Luo, Y. Jing, X. Wang, B. Peng, L. Liu, C. Hu, H. Zhou, Y. Wei, X. Chen, Q. Feng, Structure and energy storage performance of Ba-modified AgNbO3 leadfree antiferroelectric ceramics, Ceram. Int. 45 (2019) 5559–5565. [22] Z. Yang, F. Gao, H. Du, L. Jin, L. Yan, Q. Hu, Y. Yu, S. Qu, X. Wei, Z. Xu, Y.-J. Wang, Grain size engineered lead-free ceramics with both large energy storage density and ultrahigh mechanical properties, Nano Energy 58 (2019) 768–777. [23] C. Ang, Z. Yu, High, purely electrostrictive strain in lead-free dielectrics, Adv. Mater. 18 (2006) 103–106. [24] S.-T. Zhang, A.B. Kounga, W. Jo, C. Jamin, K. Seifert, T. Granzow, J. Rödel, D. Damjanovic, High-strain lead-free antiferroelectric electrostrictors, Adv. Mater. 21 (2009) 4716–4720. [25] L. Jin, W. Luo, L. Wang, Y. Tian, Q. Hu, L. Hou, L. Zhang, X. Lu, H. Du, X. Wei, G. Liu, Y. Yan, High thermal stability of electric field-induced strain in (1−x) (Bi0.5Na0.5)TiO3-xBa0.85Ca0.15Ti0.9Zr0.1O3 lead-free ferroelectrics, J. Eur. Ceram. Soc. 39 (2019) 277–286. [26] W. Bai, D. Chen, P. Zheng, J. Zhang, B. Shen, J. Zhai, Z. Ji, Grain-orientated leadfree BNT-based piezoceramics with giant electrostrictive effect, Ceram. Int. 43 (2017) 3339–3345. [27] W. Bai, L. Li, W. Wang, B. Shen, J. Zhai, Phase diagram and electrostrictive effect in BNT-based ceramics, Solid State Commun. 206 (2015) 22–25. [28] J. Hao, W. Bai, W. Li, B. Shen, J. Zhai, Phase transitions, relaxor behavior, and electrical properties in (1-x)(Bi0.5Na0.5)TiO3-x(K0.5Na0.5)NbO3 lead-free piezoceramics, J. Mater. Res. 27 (2012) 2943–2955. [29] L. Jin, R. Huo, R. Guo, F. Li, D. Wang, Y. Tian, Q. Hu, X. Wei, Z. He, Y. Yan, G. Liu, Diffuse phase transitions and giant electrostrictive coefficients in lead-free Fe3+doped 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ferroelectric ceramics, ACS Appl. Mater. Interfaces 8 (2016) 31109–31119. [30] F. Li, L. Jin, R. Guo, High electrostrictive coefficient Q33 in lead-free Ba(Zr0.2Ti0.8) O3-x(Ba0.7Ca0.3)TiO3 piezoelectric ceramics, Appl. Phys. Lett. 105 (2014) 232903. [31] R. Zuo, H. Qi, J. Fu, J. Li, M. Shi, Y. Xu, Giant electrostrictive effects of NaNbO3BaTiO3 lead-free relaxor ferroelectrics, Appl. Phys. Lett. 108 (2016) 232904. [32] X. Lu, L. Hou, L. Jin, L. Wang, Y. Tian, K. Yu, Q. Hu, L. Zhang, X. Wei, Structure evolution and exceptionally ultra-low hysteresis unipolar electric field-induced strain in (1−x)NaNbO3-xBaTiO3 lead-free ferroelectrics, Ceram. Int. 44 (2018) 5492–5499. [33] X. Lu, L. Hou, L. Jin, D. Wang, Q. Hu, D.O. Alikin, A.P. Turygin, L. Wang, L. Zhang, X. Wei, Origin of composition-insensitive electrostrictive coefficient and continuous decrease of domain wall density in (1−x)NaNbO3-xBaTiO3 lead-free ferroelectrics, J. Eur. Ceram. Soc. 38 (2018) 3127–3135.
[34] W. Liu, X. Ren, Large piezoelectric effect in Pb-free ceramics, Phys. Rev. Lett. 103 (2009) 257602. [35] L. Jin, D. Damjanovic Porokhonskyy, Separation of piezoelectric grain resonance and domain wall dispersion in Pb(Zr,Ti)O3 ceramics, Appl. Phys. Lett. 94 (2009) 212906. [36] Z. Xing, L. Jin, T. Wang, Q. Hu, Y. Feng, X. Wei, Achieving both high d33 and high Qm for the Pb(Zr0.26Sn0.26Ti0.48)1-xFexO3-x/2 ternary system for use in high-power ultrasonic transducers, J. Electron. Mater. 43 (2014) 3905–3911. [37] P. Hansen, D. Hennings, H. Schreinemacher, Dielectric properties of acceptor-doped (Ba,Ca)(Ti,Zr)O3 ceramics, J. Electroceram. 2 (1998) 85–94. [38] K. Uchino, S. Nomura, Critical exponents of the dielectric constants in diffusedphase-transition crystals, Ferroelectrics 44 (1982) 55–61. [39] M.C. Ehmke, J. Glaum, M. Hoffman, J.E. Blendell, K.J. Bowman, The effect of electric poling on the performance of lead-free (1−x)Ba(Zr0.2Ti0.8)O3-x (Ba0.7Ca0.3)TiO3 piezoceramics, J. Am. Ceram. Soc. 96 (2013) 3805–3811. [40] Y. Tian, X. Chao, L. Jin, L. Wei, P. Liang, Z. Yang, Polymorphic structure evolution and large piezoelectric response of lead-free (Ba,Ca)(Zr,Ti)O3 ceramics, Appl. Phys. Lett. 104 (2014) 112901. [41] L. Jin, J. Qiao, L. Hou, L. Wang, L. Zhang, X. Lu, H. Du, X. Wei, Y. Yan, G. Liu, High electrostrictive effect in La3+-doped Ba(Zr0.2Ti0.8)O3 lead-free ferroelectrics, J. Alloy. Comp. 776 (2019) 599–605. [42] L. Jin, W. Luo, L. Hou, Y. Tian, Q. Hu, L. Wang, L. Zhang, X. Lu, H. Du, X. Wei, Y. Yan, G. Liu, High electric field-induced strain with ultra-low hysteresis and giant electrostrictive coefficient in barium strontium titanate lead-free ferroelectrics, J. Eur. Ceram. Soc. 39 (2019) 295–304. [43] H. Pan, J. Zhang, X. Jia, H. Xing, J. He, J. Wang, F. Wen, Large electrostrictive effect and high optical temperature sensing in Bi0.5Na0.5TiO3-BaTiO3(Sr0.7Bi0.18Er0.02)TiO3 luminescent ferroelectrics, Ceram. Int. 44 (2018) 5785–5789. [44] J. Hao, Z. Xu, R. Chu, W. Li, P. Fu, J. Du, G. Li, Structure evolution and electrostrictive properties in (Bi0.5Na0.5)0.94Ba0.06TiO3–M2O5 (M=Nb, Ta, Sb) lead-free piezoceramics, J. Eur. Ceram. Soc. 36 (2016) 4003–4014. [45] L. Jin, J. Qiao, L. Wang, L. Hou, R. Jing, J. Pang, L. Zhang, X. Lu, X. Wei, G. Liu, Y. Yan, Ultra-low hysteresis electric field-induced strain with high electrostrictive coefficient in lead-free Ba(ZrxTi1-x)O3 ferroelectrics, J. Alloy. Comp. 784 (2019) 931–938. [46] J. Hao, W. Li, J. Zhai, H. Chen, Progress in high-strain perovskite piezoelectric ceramics, Mater. Sci. Eng. R 135 (2019) 1–57. [47] L. Jin, J. Qiao, L. Hou, Y. Tian, Q. Hu, L. Wang, X. Lu, L. Zhang, H. Du, X. Wei, G. Liu, Y. Yan, A strategy for obtaining high electrostrictive properties and its application in barium stannate titanate lead-free ferroelectrics, Ceram. Int. 44 (2018) 21816–21824. [48] J. Hao, Z. Xu, R. Chu, W. Li, J. Du, Lead-free electrostrictive (Bi0.5Na0.5)TiO3(Bi0.5K0.5)TiO3-(K0.5Na0.5)NbO3 ceramics with good thermostability and fatiguefree behavior, J. Mater. Sci. 50 (2015) 5328–5336. [49] T. Vu Diem Ngoc, D. Thi Hinh, H.-S. Han, W. Jo, J.-S. Lee, Lead-free Bi1/ 2(Na0.82K0.18)1/2TiO3 relaxor ferroelectrics with temperature insensitive electrostrictive coefficient, Ceram. Int. 39 (2013) S119–S124. [50] K. Uchino, S. Nomura, L.E. Cross, S.J. Jang, R.E. Newnham, Electrostrictive effect in lead magnesium niobate single-crystals, J. Appl. Phys. 51 (1980) 1142–1145. [51] S.-T. Zhang, F. Yan, B. Yang, W. Cao, Phase diagram and electrostrictive properties of Bi0.5Na0.5TiO3–BaTiO3–K0.5Na0.5NbO3 ceramics, Appl. Phys. Lett. 97 (2010) 122901. [52] Y. Guo, M. Gu, H. Luo, Y. Liu, R.L. Withers, Composition-induced antiferroelectric phase and giant strain in lead-free (Nay,Biz)Ti1-xO3(1-x)-xBaTiO3 ceramics, Phys. Rev. B 83 (2011) 054118. [53] A. Ullah, H.B. Gul, A. Ullah, M. Sheeraz, J.-S. Bae, W. Jo, C.W. Ahn, I.W. Kim, T.H. Kim, Giant room-temperature electrostrictive coefficients in lead-free relaxor ferroelectric ceramics by compositional tuning, Apl. Mater. 6 (2018) 016104.
21320