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Reduced dielectric loss and high piezoelectric constant in Ce and Mn co-doped BiScO3-PbCexTi1-xO3-Bi(Zn0.5Ti0.5)O3 ceramics
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Reduced dielectric loss and high piezoelectric constant in Ce and Mn codoped BiScO3-PbCexTi1-xO3-Bi(Zn0.5Ti0.5)O3 ceramics Zhuang Liua, Bo Wua,b, Jiagang Wua, a b
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Department of Materials Science, Sichuan University, Chengdu 610064, China Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu, China
A R T I C LE I N FO
A B S T R A C T
Keywords: BiScO3-PbTiO3 Composition design Dielectric loss Piezoelectric constant
MnO2-doped 0.99(0.36BiScO3-0.64PbTi1-xCexO3)-0.01Bi(Zn0.5Ti0.5)O3 (BS-PTC-BZT-MnO2) ceramics are fabricated by the solid-state method. Here, it's firstly reported that Ce element can reduce dielectric loss (tan δ) and suppress the decrease of piezoelectric constant (d33) simultaneously. Effects of Ce contents on the structure and electrical properties of BS-PTC-BZT-MnO2 ceramics are studied. The ceramics (x = 0.02) with MPB (rhombohedral-tetragonal) possess low dielectric loss (tan δ = 1.36%, 1 kHz) and high piezoelectric constant (d33 = 360 pC/N) simultaneously, which is superior to most reported BS-PT. Besides, excellent comprehensive properties including high Curie temperature (TC = 422 °C), large dielectric constant (ɛr = 1324), and high remnant polarization (Pr = 35.1 µC/cm2) are obtained. Asymmetric S-E and P-E hysteresis loops indicate that defects and oxygen vacancies are induced by multi-valence elements (Ce and Mn), which is the origin for reducing tan δ. In addition, good thermal stability of piezoelectric and dielectric properties is observed. These results indicate that Ce and Mn co-doped BS-PTC-BZT-MnO2 ceramics can be well applied as power electronic devices under high temperature.
1. Introduction Lead zirconate-titanate (PZT) piezoceramics have been widely applied in some devices due to their outstanding piezoelectric properties [1–5]. However, the limit of usage temperature is half of the Curie temperature (TC). Unfortunately, the TC of most PZT-based ceramics is less than 350 °C [1,6–8]. Therefore, low TC makes it difficult for PZTbased ceramics to work at above 200 °C because they may depolarize absolutely under high temperature. Recently, many high-temperature piezoelectric materials are developed and become the competitive competitor to PZT, such as BiFeO3 (BFO) and (K, Na)NbO3 (KNN) [9–12]. Afterwards, lots of piezoelectric materials are reported with high TC including CaBi2Nb2O9 (TC ~ 930 °C) [13,14] and Ca0.9(Li0.5Ce0.25Pr0.25)0.1Bi2Nb2O9 (TC ~ 940 °C) [15]. However, low piezoelectric constant (d33 < 40 pC/N) is often observed in these materials [13–15]. Bi(Me)O3-PbTiO3 systems (Me = Sc, In, Y, Yb, etc) have attracted more attention, possessing both high TC and large d33 [16–19]. Among them, BiScO3-PbTiO3 (BS-PT) with MPB composition (36 mol% BiScO3) owns large d33 (d33 = 450 pC/N) as compared with PZT, and even higher TC (TC = 450 °C) can be found [19], showing excellent prospects in the field of high-temperature applications. Afterwards, the
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researchers found that doping ABO3 end numbers could promote d33 effectively in BS-PT [20–22], and our recent work also indicated that the addition of Bi(ZnTi)0.5O3 could enhance d33 obviously (d33 = 520 pC/N) [22]. However, one of the most important drawbacks of BS-PTbased materials is high dielectric loss (tan δ > 4% in BS-PT and tan δ > 6% in BS-PT-ABO3, 1 kHz) [6,8,22–24], leading to a relatively high degree of heat generation and energy dissipation as high power electronic devices when working under high resonance frequency [6,8,24]. Previously, some measurements have been employed to decrease tan δ of BS-PT-ABO3 ternary systems [6,8,24,25]. Among them, one of the most effective methods is to introduce defects and oxygen vacancies using multi-valence elements such as Mn and Fe [8], and then tan δ can be reduced effectively. It was reported that the defects and oxygen vacancies produced by multi-valence elements may diffuse into domain boundaries and lower the overall energy of the ceramics, resulting in the pinning behavior of the 180° domain motions and considering as one of the most critical contributions to reduce tan δ [8,24]. Unfortunately, their d33 deteriorates greatly (d33 ≤ 300 pC/N) and dielectric constant (ɛr) also decreases significantly to less than 103 [6,8,24,25], which is only nearly half of BS-PT-BZT (ɛr = 1825) [22]. Therefore, it is wondered whether high d33 as well as low tan δ can be developed simultaneously in BS-PT-BZT by the composition design and
Corresponding author. E-mail addresses: [email protected], [email protected] (J. Wu).
https://doi.org/10.1016/j.ceramint.2018.06.065 Received 5 June 2018; Received in revised form 8 June 2018; Accepted 9 June 2018 0272-8842/ © 2018 Published by Elsevier Ltd.
Please cite this article as: Liu, Z., Ceramics International (2018), https://doi.org/10.1016/j.ceramint.2018.06.065
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bismuth (Bi) in the high-temperature sintering process [1,6,8]. The solution after ball-milled for 24 h with alcohol was dried and calcined at 780 °C for 3 h in air. The calcined mixtures were adhered using polyvinyl alcohol (PVA) and then were pressed into disks with ~ 10.0 mm diameter and ~ 6.0 mm thickness. Green disks samples were sintered at 500 °C for 3 h in air for burning out the PVA binder, and then the samples were embedded in the calcined powders of same composition and sintered at 1120 °C for 2 h. Silver was pasted on both sides of as-sintered samples and fired at 600 °C for 10 min. For electrical characteristics, samples were polarized at 120 °C in silicon oil under a dc field of 50 kV/cm. X-ray diffraction (XRD, Bruker D8 Advanced XRD, Bruker AXS, Inc., Madison, WI) with a Cu Kα radiation (λ = 1.5406 Å) was used to identify the phase structure of the sintered samples. The field emissionscanning electron microscopy (FE-SEM, JSM7500, Japan) was applied to characterize the morphologies evolutions. The planar electromechanical coupling factor (kp) was calculated through the resonanceantiresonance method using an impedance analyzer (HP4294A). The temperature dependence of the dielectric properties was gained by an LCR meter (HP 4980 Agilent, U.S.A. and TH 2816A) equipped with a temperature-controlled box. Bipolarization hysteresis loops (P-E) were obtained using a Radiant Precise Workstation (Radiant Technologies, Medina NY), measured at f = 10 Hz. The strain versus electric field curves (S-E) were gained using a strain instrument (aixACCT TF Analyzer 2000, Germany). d33 was determined by a Belincourt meter (ZJ-3A, China). To measure the thermal stability of d33, poled samples were heated to various temperatures and hold for 30 min, and then d33 was gained by a Belincourt meter.
Fig. 1. (a) XRD patterns of the ceramics with different Ce contents as well as samples doped with x = 0.02 Ce only. (b) Partial enlarged drawings of 2θ = 30–33°.
optimization. In this work, we co-doped 1 mol% MnO2 as a sintering aid and another multi-valence element Ce to BS-PT-BZT ceramics. Through optimizing the contents of Ce, we realize the established objectives in BiScO3-PbTi1-xCexO3-Bi(Zn0.5Ti0.5)O3-MnO2 (BS-PTC-BZT-MnO2) ceramics with MPB of rhombohedral-tetragonal (R-T) phase coexistence. Low dielectrics loss (tan δ = 1.36%) and large piezoelectric constant (d33 = 360 pC/N) together with a high TC (TC = 422 °C) are observed at x = 0.02. In addition, the related physical mechanism for enhanced properties is also discussed. We believe that this work can optimize piezoelectric constant and dielectric loss simultaneously.
3. Results and discussions The XRD patterns of the ceramics with 2θ = 20–70° are shown in Fig. 1(a), and partial enlarged drawings of 2θ = 30–33° are also exhibited in Fig. 1(b) to identify phase accurately. The XRD patterns confirm that all the ceramics are pure perovskite phases without secondary phases, indicating that Ce and MnO2 are diffused into BS-PTBZT matrix. According to our previous reports, the BS-PT-BZT ceramics possess the MPB of R-T phase boundary [22]. It is found from Fig. 1(b) that the phase structure of this work remains unchanged after introducing Ce and/or MnO2, and the R-T phase coexistence can be observed in all compositions. Fig. 2 shows the SEM photographs derived from the surfaces of the
2. Experimental section 1 mol% MnO2 modified 0.99(0.36BiScO3-0.64PbTi1-xCexO3)-0.01Bi (Zn0.5Ti0.5)O3 (BS-PTC-BZT-MnO2) ceramics (x = 0, 0.01, 0.015, 0.02, 0.025, 0.03, and 0.04) were prepared by the conventional solid-state process method. Starting raw materials including Bi2O3 (99%), Sc2O3 (99.99%), PbO (99%), TiO2 (99%), ZnO (99.9%), MnO2 (99.9%), and CeO2 (99.99%) were weighed according to their stoichiometric ratio. The excess 2 mol% Bi2O3 was added to compensate the evaporation of
Fig. 2. FE-SEM images of surfaces of BS-PTC-BZT-MnO2 ceramics with (a)–(e) different Ce contents, and (f) x = 0.02 Ce doped only. 2
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Fig. 3. Temperature-dependent (a) dielectric constant (ɛr) and (b) dielectric loss (tan δ) of Ce and/or MnO2 doped ceramics as a function of Ce contents, and the inset in (a) is TC against compositions.
Fig. 4. (a) Piezoelectric and (b) dielectric properties of Ce and/or MnO2 doped ceramics as a function of Ce contents.
between Mn and Ce during the substitution of Ti results in formation of less oxygen vacancies, leading to weaker assistance effect of mass transport. Eqs. (1)–(5) can represent the above process [26,27]. VO·· and ′ (A = Ce and Mn) present oxygen vacancies and defect-dipole ATi clusters, respectively. 3MnO2 → MnO + Mn2O3 + OO
(1)
2CeO2 → Ce2O3 + 1/2OO
(2)
Ce2 O3 + 2TiO2 → 2Ce′Ti +
V ⋅⋅O
+ 3OO
(3)
Mn2 O3 + 2TiO2 → 2Mn′Ti + V ⋅⋅O + 3OO
(4)
MnO + TiO2 → Mn′Ti + V ⋅⋅O + OO
(5)
On the other hand, excessive oxides may not completely dissolve in the solutions, resulting in assemble at grain boundaries and then restraining the grain growth [8]. In summary, the Ce and MnO2 co-doped ceramics possess small grain sizes with dense structure and uniform distribution. The temperature dependence of dielectric properties of the samples is shown in Fig. 3, measured at f = 1 kHz and 25–500 °C. The ferroelectric-paraelectric phase transition with increasing temperatures is revealed by the appearance of dielectric maximum. Curie temperature (TC) can be gained from the temperature at the dielectric peak, and the curves of TC vs. compositions are also exhibited in the inset of Fig. 3(a). In Fig. 3(a), it is found that TC decreases monotonously from 431 °C to 385 °C with increasing Ce contents (x = 0.00 to x = 0.04). It is found from Fig. 3(b) that dielectric loss (tan δ) of all samples with different Ce contents shows a stable changing tendency with increasing
Fig. 5. Comparison of BS-PT-based ceramic systems against their d33 and tan δ.
samples. All the specimens own a dense microstructure and uniform grains distribution. We can find from Fig. 2(e) and (f) that the samples with MnO2/Ce possess a larger grain size of approximately 3.5–4 µm than those of co-doped ones. Similar results are also observed in previous Mn-modified BS-PT-based systems [8,24]. According to previous reports, the concentration of oxygen vacancies increases due to the Ti substitution for multi-valence ions (Mn or Ce), which promotes mass transport and further assists grain growth during sintering process [8]. However, it is found from Fig. 2(a)–(e) that the average grain size becomes much smaller of ~ 1 µm after the addition of Ce, which can be explained in two aspects. On the one hand, the competitive relationship 3
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Fig. 6. (a) P-E loops of the samples. (b) Pr and (c) Eint values as a function of compositions.
Fig. 7. (a) S-E curves as a function of compositions. (b) Relevant parameters in S-E loops. (c) Asymmetry factor γs vs. compositions.
tan δ of the samples with x = 0.02 is higher than those of co-doped ones, but is more stable with increasing temperatures. Therefore, the ceramics with Ce and MnO2 possess high TC and low tan δ. Piezoelectric and dielectric properties of Ce and/or MnO2-doped ceramics with different Ce contents are exhibited in Fig. 4, measured at f = 1 kHz and room temperature. In Fig. 4(a), It is found that d33 and kp firstly increase with increasing Ce contents and then decrease with further doping, reaching the maximum values (d33 = 360 pC/N and kp = 0.512) for x = 0.02. Besides, the samples with x = 0.02 Ce (without MnO2) possess better piezoelectric properties (d33 = 380 pC/N and kp = 0.525) than those of co-doped ones, indicating that MnO2 does harm to piezoelectric properties [6,8,24,25]. It is found from Fig. 4(b) that with increasing Ce contents, dielectric constant (ɛr) firstly increases (x = 0.00–0.02) and then decreases with continuous dopants (x = 0.02–0.04), reaching the optimum values (ɛr = 1324) for x = 0.02. As for tan δ, it keeps a low level (tan δ < 1.7%) with the increase of Ce (x = 0.00–0.04) [Fig. 4(b)]. tan δ of the samples with x = 0.02 Ce (without MnO2) is 1.85%, which is higher than those of codoped samples, indicating that MnO2 can effectively reduce tan δ [6,8,24,25]. The optimized electrical property of d33 = 360 pC/N and
Fig. 8. Physical model for reducing tan δ in this work, in which defects and oxygen vacancies are amplified to clarify the process more clearly.
temperatures. As shown in the insert chart of Fig. 3(b), the Ce and MnO2 co-modified samples exhibit a lower tan δ than those of Mnmodified ones, indicating that Ce can usefully decrease tan δ. In addition, lower tan δ will be observed when more Ti is replaced by Ce. In addition, the temperature dependence of tan δ with x = 0.02 Ce (without MnO2) is also shown in the inset of Fig. 3(b). It is found that
Fig. 9. (a) d33 of the samples after annealing at various temperatures. (b) Curves of Td and TC against compositions. 4
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tan δ = 1.36% is observed at x = 0.02. This result indicates that Ce can suppress the deterioration of piezoelectric properties and keeps a stable low tan δ simultaneously. In addition, combined with SEM images [Fig. 2], we find that small grains are useful to enhance piezoelectric and dielectric properties in co-doped samples, while large grains are bad to the enhancement of electrical properties [24]. To evaluate the advance of this work, the statistics including d33 and tan δ [6,8,23,24,28,29] are gathered in Fig. 5. Higher d33 together with low tan δ can be achieved in this work. We realize the target of high d33 (d33 = 360 pC/N) and low tan δ (tan δ = 1.36%) simultaneously. As a result, the comprehensive properties in this work are superior to most previous reports of BS-PT-based ceramics. Fig. 6(a) shows the room-temperature polarization hysteresis loops (P-E) of the ceramics. We can find from Fig. 6(a) that all P-E loops are saturated but asymmetric, demonstrating the existence of internal bias field (Eint) [6,8,24]. It is found from Fig. 6(b) that the remnant polarization (Pr) initially decreases from 36.9 µC/cm2 (x = 0.00) to 35.1 µC/ cm2 (x = 0.02), which may result from the pinning of domain walls caused by the defects and oxygen vacancies produced by Ce and the acceptor type substitution of Ti for Ce in the lattice [24]. When further doping Ce from x = 0.02 to x = 0.04, Pr increases to 38.7 µC/cm2, resulting from the production of more oxygen vacancies induced by excessive addition of Ce. Combined with SEM images [Fig. 2], we find that large grains enhance ferroelectric properties, while small grains are harmful to electrical properties [6,23]. Eint values can be calculated by the Eq. (6) and shown in Fig. 6(c).
Eint = (E+ − E−)/2
chemical reaction [Eqs. (1)–(5)], compositing with matrix well and lowering the overall energy of the ceramics, which leads to the pinning of the 180° domain motions, finally reduce tan δ effectively. Fig. 9 shows the thermal stability of d33 in all the ceramics. It is found from Fig. 9(a) that d33 is stable with increasing temperatures initially and then rapidly drops to zero when the temperature approaches to TC. Depolarization temperature (Td) can be derived from the mutational point in curves of d33 vs. temperature. Although the temperature stability of d33 decreases slightly with increasing Ce contents, their d33 still keeps stable up to more than 350 °C, which is superior to PZT [1,6–8]. Fig. 9(b) presents the Td and TC vs. compositions of the ceramics. Similar changing trend of Td and TC indicates a good thermal stability of BS-PTC-BZT-MnO2 ceramics. 4. Conclusion We realize the excellent comprehensive properties (d33 = 360 pC/N and tan δ = 1.36%) in BS-PTC-BZT-MnO2 ceramics (MPB of R-T phase coexistence) with high TC of 422 °C by adding MnO2 and refining Ce contents. Partially replacing Ti with Ce can achieve a low dielectric loss and suppress the decrease of piezoelectric constant simultaneously. In addition, the temperature-dependent piezoelectric and dielectric properties are stable in a wide temperature range. Asymmetric P-E and S-E loops confirm the existence of defects and oxygen vacancies induced by Ce and Mn, which reduce dielectric loss effectively. We believe that BSPTC-BZT-MnO2 system can be well applied to high-temperature piezoelectric fields as power electronic devices.
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The initial increase of Eint from x = 0.00 to x = 0.02 is attributed to the space charges produced by the addition of Ce [8,24]. Then the decrease of Eint with further doping may be due to the competitive relation between Ce and Mn. Mn4+ and Ti4+ possess the similar ionic radius (0.0645 nm and 0.0605 nm, respectively), while much larger radius of Ce4+ (0.087 nm) makes it difficult for Ce4+ to occupy the sites of Ti4+. Moreover, the Eint of the compositions with x = 0.02 (without MnO2) (Eint = 2.15 kV/cm) plus the Eint of x = 0.00 (without Ce) (Eint = 2.0 kV/cm) is much larger than those of co-doped component (Eint = 2.32 kV/cm), further confirming the competitive relationship of the Ti substitution for multi-valence elements (Ce and Mn). As a result, the ceramics possess large Pr, and the existence of Eint confirms the existence of defects and oxygen vacancies induced by Ce and Mn, which helps reduce tan δ, as discussed above. Room-temperature strain loops (S-E) of all the samples are shown in Fig. 7(a). Butterfly-shaped loops can be observed in all compositions. However, all curves behave asymmetric, further implying the existence of Eint and the formation of defects and oxygen vacancies [8]. In addition, with increasing Ce contents from x = 0.00 to x = 0.02, S-E curves become more and more asymmetric, and then the degree of asymmetry becomes smaller with further doping. According to previous reports, any asymmetry in S-E loops can be expressed by an asymmetry factor γs, defined by the Eq. (7) [30]. Relevant parameters are shown in Fig. 7(b).
γs = (ΔS+ − ΔS −)/(ΔS+ + ΔS −)
Acknowledgement Authors gratefully acknowledge the supports of the National Science Foundation of China (NSFC Nos. 51722208 and 51472169). We also appreciate Wang Hui from the Analytical & Testing Center of Sichuan University for her help with SEM characterization. References [1] J.G. Chen, H.D. Shi, G.X. Liu, J.R. Cheng, S.X. Dong, Temperature dependence of dielectric, piezoelectric and elastic properties of BiScO3-PbTiO3 high temperature ceramics with morphotropic phase boundary (MPB) composition, J. Alloy. Compd. 537 (1) (2012) 280–285. [2] A.H. Qureshi, G. Shabbir, D.A. Hall, On the synthesis and dielectric studies of (1-x) Bi(Mg1/2Zr1/2)O3-xPbTiO3 piezoelectric ceramic system, Mater. Lett. 61 (23) (2007) 4482–4484. [3] J.G. Chen, J.R. Cheng, Enhanced thermal stability of lead-free high temperature 0.75BiFeO3−0.25BaTiO3 ceramics with excess Bi content, J. Alloy. Compd. 589 (9) (2014) 115–119. [4] Z.H. Yao, C.B. Xu, Z.J. Wang, Z. Song, Y.M. Zhang, W. Hu, H. Hao, M.H. Cao, H.X. Liu, Microstructure, ferro-piezoelectric and thermal stability of SiO2 modified BiFeO3-BaTiO3 high temperature piezoceramics, J. Mater. Sci. 26 (1) (2015) 479–484. [5] K. Yamakawa, K. Imai, O. Arisumi, T. Arikado, M. Yoshioka, T. Owada, K.O. kumura, Novel Pb(Ti, Zr)O3 (PZT) crystallization technique using flash lamp for ferroelectric RAM (FeRAM) embedded LSIs and one transistor type FeRAM devices, Jpn. J. Appl. Phys. 41 (4) (2002) 2630–2634. [6] J.G. Chen, Y.J. Dong, J.R. Cheng, Reduced dielectric loss and strain hysteresis in (0.97-x)BiScO3-xPbTiO3−0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceram. Int. 41 (8) (2015) 9828–9833. [7] Z. Gubinyi, C. Batur, A. Sayir, F. Dynys, Electrical properties of PZT piezoelectric ceramic at high temperatures, J. Electroceram. 20 (2) (2008) 95–105. [8] J.G. Chen, G.X. Jin, C.M. Wang, J.R. Cheng, Reduced dielectric loss and strain hysteresis in Fe and Mn comodified high-temperature BiScO3-PbTiO3 ceramics, J. Am. Ceram. Soc. 97 (12) (2014) 3890–3896. [9] J.G. Wu, Z. Fan, D.Q. Xiao, J.G. Zhu, J. Wang, Multiferroic bismuth ferrite-based materials for multifunctional applications: ceramic bulks, thin films and nanostructures, Prog. Mater. Sci. 84 (2016) 335–402. [10] J.G. Wu, D.Q. Xiao, J.G. Zhu, Potassium-sodium niobate lead-free piezoelectric materials: past, present, and future of phase boundaries, Chem. Rev. 115 (7) (2015) 2559–2595. [11] Y.Y. Wang, L. Hu, Q.L. Zhang, H. Yang, Phase transition characteristics and associated piezoelectricity of potassium-sodium niobate lead-free ceramics, Dalton Trans. 44 (30) (2015) 13688–13699. [12] H. Tian, C.P. Hu, X.D. Meng, Z.X. Zhou, G. Shi, Dielectric, piezoelectric, and elastic properties of K0.8Na0.2NbO3 single crystals, J. Mater. Chem. C 3 (37) (2015)
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It is found from Fig. 7(c) that γs firstly increases and then decreases with further doping, reaching the maximum value for x = 0.02. This result is accordance with the variation of Eint [Fig. 6(c)], also confirming the production of defects and oxygen vacancies, which can reduce tan δ. Besides, the ceramics with x = 0.02 (without MnO2) possess much lower γs than those of co-doped samples, indicating that the co-doped ceramics possess more defects and oxygen vacancies, and then tan δ can be further reduced [Fig. 4(b)]. Based on the evidences of existence of defects and oxygen vacancies, a detailed physical model for reducing tan δ is supplied, as shown in Fig. 8. Multi-valence elements (Ce and Mn) diffuse into BS-PT-BZT matrix, and defects and oxygen vacancies are produced after complex 5
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9609–9614. [13] J. Chen, J. Yuan, S.M. Bao, Y.J. Wu, G. Liu, Q. Chen, D.Q. Xiao, J.G. Zhu, Effects of (Li, Ce, Y) co-substitution on the properties of CaBi2Nb2O9 high temperature piezoceramics, Ceram. Int. 6 (43) (2017) 5002–5006. [14] X.D. Zhang, H.X. Yan, R.M.J. Reece, Effect of A site substitution on the properties of CaBi2Nb2O9 ferroelectric ceramics, J. Am. Ceram. Soc. 91 (9) (2010) 2928–2932. [15] Z.H. Peng, Q. Chen, Y.D. Wang, D.Q. Xin, D.Q. Xiao, J.G. Zhu, Enhancement of piezoelectric properties of (LiCePr)-multidoped CaBi2Nb2O9 high temperature ceramics, Mater. Lett. 15 (107) (2013) 14–16. [16] R.E. Eitel, C.A. Randall, T.R. Shrout, P.W. Rehring, W. Hackenberger, S.E. Park, New high temperature morphotropic phase boundary piezoelectrics based on Bi (Me)O3-PbTiO3 ceramics, Jpn. J. Appl. Phys. 40 (10) (2014) 5999–6002. [17] C.A. Randall, R. Eitel, B. Jones, T.R. Shrout, D.I. Woodward, I.M. Reaney, Investigation of a high TC piezoelectric system: (1-x)Bi(Mg1/2Ti1/2)O3-xPbTiO3, J. Appl. Phys. 95 (7) (2004) 3633–3639. [18] M.R. Suchomel, P.K. Davies, Predicting the position of the morphotropic phase boundary in high temperature PbTiO3-Bi(B′B”)O3 based dielectric ceramics, J. Appl. Phys. 96 (8) (2004) 4405–4410. [19] R.E. Eitel, C.A. Randall, T.R. Shrout, S.E. Park, Preparation and characterization of high temperature perovskite ferroelectrics in the solid solution (1-x)BiScO3xPbTiO3, Jpn. J. Appl. Phys. 41 (4A) (2002) 2099–2104. [20] I. Sterianou, I.M. Reaney, D.C. Sinclair, D.I. Woodward, High-temperature (1-x) BiSc1/2Fe1/2O3-xPbTiO3 piezoelectric ceramics, Appl. Phys. Lett. 87 (24) (2005) 299. [21] Z.H. Liu, A.R. Paterson, H. Wu, P. Gao, W. Ren, Z.G. Ye, Synthesis, structure and
[22]
[23]
[24]
[25] [26] [27] [28]
[29]
[30]
6
piezo-/ferroelectric properties of novel bismuth-containing ternary complex perovskite solid solution, J. Mater. Chem. C 5 (16) (2017) 3916–3923. Z. Liu, C.L. Zhao, J.F. Li, K. Wang, J.G. Wu, Large strain and temperature-insensitive piezoelectric effect in high-temperature piezoelectric ceramics, J. Mater. Chem. C 6 (3) (2018) 456–463. Q.W. Liao, X.S. Chen, X.C. Chu, F. Zeng, D. Guo, Effect of Fe doping on the structure and electric properties of relaxor type BSPT-PZN piezoelectric ceramics near the morphotropic phase boundary, Sens. Actuators A-Phys. 201 (10) (2013) 222–229. J.G. Chen, Z.Q. Hu, H.D. Shi, M.Y. Li, S.X. Dong, High-power piezoelectric characteristics of manganese-modified BiScO3-PbTiO3 high-temperature piezoelectric ceramics, J. Phys. D: Appl. Phys. 45 (46) (2012) 465303. J. Ryu, S. Priya, C. Sakaki, K. Uchino, High power piezoelectric characteristics of BiScO3-PbTiO3-Pb(Mn1/3Nb2/3)O3, Jpn. J. Appl. Phys. 41 (41) (2002) 6040–6044. X.J. Cheng, Z.W. Li, J.G. Wu, Colossal permittivity in ceramics of TiO2 co-doped with niobium and trivalent cation, J. Mater. Chem. A 3 (11) (2015) 5805–5810. Z.W. Li, J.G. Wu, W.J. Wu, Composition dependence of colossal permittivity in (Sm0.5Ta0.5)xTi1-xO2 ceramics, J. Mater. Chem. C 3 (35) (2015) 9206–9216. T.Y. Ansell, D.P. Cann, Piezoelectric properties of the high temperature MPB xPbTiO3-(1-x)[BiScO3-Bi(Ni1/2Ti1/2)O3] composition, J. Electroceram. 31 (1) (2013) 159–167. T. Sebastian, I. Sterianou, D.C. Sinclair, A.J. Bell, D.A. Hall, I.M. Reaney, High temperature piezoelectric ceramics in the Bi(Mg1/2Ti1/2)O3-BiFeO3-BiScO3-PbTiO3 system, J. Electroceram. 25 (2) (2010) 130–134. N. Balke, D.C. Lupascu, T. Granzow, J. Rödel, Fatigue of lead zirconate titanate ceramics. I: unipolar and DC loading, J. Am. Ceram. Soc. 90 (4) (2007) 1081–1087.
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Ceramics International journal homepage: www.elsevier.com/locate/ceramint
Reduced dielectric loss and high piezoelectric constant in Ce and Mn codoped BiScO3-PbCexTi1-xO3-Bi(Zn0.5Ti0.5)O3 ceramics Zhuang Liua, Bo Wua,b, Jiagang Wua, a b
⁎
Department of Materials Science, Sichuan University, Chengdu 610064, China Sichuan Province Key Laboratory of Information Materials and Devices Application, Chengdu University of Information Technology, Chengdu, China
A R T I C LE I N FO
A B S T R A C T
Keywords: BiScO3-PbTiO3 Composition design Dielectric loss Piezoelectric constant
MnO2-doped 0.99(0.36BiScO3-0.64PbTi1-xCexO3)-0.01Bi(Zn0.5Ti0.5)O3 (BS-PTC-BZT-MnO2) ceramics are fabricated by the solid-state method. Here, it's firstly reported that Ce element can reduce dielectric loss (tan δ) and suppress the decrease of piezoelectric constant (d33) simultaneously. Effects of Ce contents on the structure and electrical properties of BS-PTC-BZT-MnO2 ceramics are studied. The ceramics (x = 0.02) with MPB (rhombohedral-tetragonal) possess low dielectric loss (tan δ = 1.36%, 1 kHz) and high piezoelectric constant (d33 = 360 pC/N) simultaneously, which is superior to most reported BS-PT. Besides, excellent comprehensive properties including high Curie temperature (TC = 422 °C), large dielectric constant (ɛr = 1324), and high remnant polarization (Pr = 35.1 µC/cm2) are obtained. Asymmetric S-E and P-E hysteresis loops indicate that defects and oxygen vacancies are induced by multi-valence elements (Ce and Mn), which is the origin for reducing tan δ. In addition, good thermal stability of piezoelectric and dielectric properties is observed. These results indicate that Ce and Mn co-doped BS-PTC-BZT-MnO2 ceramics can be well applied as power electronic devices under high temperature.
1. Introduction Lead zirconate-titanate (PZT) piezoceramics have been widely applied in some devices due to their outstanding piezoelectric properties [1–5]. However, the limit of usage temperature is half of the Curie temperature (TC). Unfortunately, the TC of most PZT-based ceramics is less than 350 °C [1,6–8]. Therefore, low TC makes it difficult for PZTbased ceramics to work at above 200 °C because they may depolarize absolutely under high temperature. Recently, many high-temperature piezoelectric materials are developed and become the competitive competitor to PZT, such as BiFeO3 (BFO) and (K, Na)NbO3 (KNN) [9–12]. Afterwards, lots of piezoelectric materials are reported with high TC including CaBi2Nb2O9 (TC ~ 930 °C) [13,14] and Ca0.9(Li0.5Ce0.25Pr0.25)0.1Bi2Nb2O9 (TC ~ 940 °C) [15]. However, low piezoelectric constant (d33 < 40 pC/N) is often observed in these materials [13–15]. Bi(Me)O3-PbTiO3 systems (Me = Sc, In, Y, Yb, etc) have attracted more attention, possessing both high TC and large d33 [16–19]. Among them, BiScO3-PbTiO3 (BS-PT) with MPB composition (36 mol% BiScO3) owns large d33 (d33 = 450 pC/N) as compared with PZT, and even higher TC (TC = 450 °C) can be found [19], showing excellent prospects in the field of high-temperature applications. Afterwards, the
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researchers found that doping ABO3 end numbers could promote d33 effectively in BS-PT [20–22], and our recent work also indicated that the addition of Bi(ZnTi)0.5O3 could enhance d33 obviously (d33 = 520 pC/N) [22]. However, one of the most important drawbacks of BS-PTbased materials is high dielectric loss (tan δ > 4% in BS-PT and tan δ > 6% in BS-PT-ABO3, 1 kHz) [6,8,22–24], leading to a relatively high degree of heat generation and energy dissipation as high power electronic devices when working under high resonance frequency [6,8,24]. Previously, some measurements have been employed to decrease tan δ of BS-PT-ABO3 ternary systems [6,8,24,25]. Among them, one of the most effective methods is to introduce defects and oxygen vacancies using multi-valence elements such as Mn and Fe [8], and then tan δ can be reduced effectively. It was reported that the defects and oxygen vacancies produced by multi-valence elements may diffuse into domain boundaries and lower the overall energy of the ceramics, resulting in the pinning behavior of the 180° domain motions and considering as one of the most critical contributions to reduce tan δ [8,24]. Unfortunately, their d33 deteriorates greatly (d33 ≤ 300 pC/N) and dielectric constant (ɛr) also decreases significantly to less than 103 [6,8,24,25], which is only nearly half of BS-PT-BZT (ɛr = 1825) [22]. Therefore, it is wondered whether high d33 as well as low tan δ can be developed simultaneously in BS-PT-BZT by the composition design and
Corresponding author. E-mail addresses: [email protected], [email protected] (J. Wu).
https://doi.org/10.1016/j.ceramint.2018.06.065 Received 5 June 2018; Received in revised form 8 June 2018; Accepted 9 June 2018 0272-8842/ © 2018 Published by Elsevier Ltd.
Please cite this article as: Liu, Z., Ceramics International (2018), https://doi.org/10.1016/j.ceramint.2018.06.065
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bismuth (Bi) in the high-temperature sintering process [1,6,8]. The solution after ball-milled for 24 h with alcohol was dried and calcined at 780 °C for 3 h in air. The calcined mixtures were adhered using polyvinyl alcohol (PVA) and then were pressed into disks with ~ 10.0 mm diameter and ~ 6.0 mm thickness. Green disks samples were sintered at 500 °C for 3 h in air for burning out the PVA binder, and then the samples were embedded in the calcined powders of same composition and sintered at 1120 °C for 2 h. Silver was pasted on both sides of as-sintered samples and fired at 600 °C for 10 min. For electrical characteristics, samples were polarized at 120 °C in silicon oil under a dc field of 50 kV/cm. X-ray diffraction (XRD, Bruker D8 Advanced XRD, Bruker AXS, Inc., Madison, WI) with a Cu Kα radiation (λ = 1.5406 Å) was used to identify the phase structure of the sintered samples. The field emissionscanning electron microscopy (FE-SEM, JSM7500, Japan) was applied to characterize the morphologies evolutions. The planar electromechanical coupling factor (kp) was calculated through the resonanceantiresonance method using an impedance analyzer (HP4294A). The temperature dependence of the dielectric properties was gained by an LCR meter (HP 4980 Agilent, U.S.A. and TH 2816A) equipped with a temperature-controlled box. Bipolarization hysteresis loops (P-E) were obtained using a Radiant Precise Workstation (Radiant Technologies, Medina NY), measured at f = 10 Hz. The strain versus electric field curves (S-E) were gained using a strain instrument (aixACCT TF Analyzer 2000, Germany). d33 was determined by a Belincourt meter (ZJ-3A, China). To measure the thermal stability of d33, poled samples were heated to various temperatures and hold for 30 min, and then d33 was gained by a Belincourt meter.
Fig. 1. (a) XRD patterns of the ceramics with different Ce contents as well as samples doped with x = 0.02 Ce only. (b) Partial enlarged drawings of 2θ = 30–33°.
optimization. In this work, we co-doped 1 mol% MnO2 as a sintering aid and another multi-valence element Ce to BS-PT-BZT ceramics. Through optimizing the contents of Ce, we realize the established objectives in BiScO3-PbTi1-xCexO3-Bi(Zn0.5Ti0.5)O3-MnO2 (BS-PTC-BZT-MnO2) ceramics with MPB of rhombohedral-tetragonal (R-T) phase coexistence. Low dielectrics loss (tan δ = 1.36%) and large piezoelectric constant (d33 = 360 pC/N) together with a high TC (TC = 422 °C) are observed at x = 0.02. In addition, the related physical mechanism for enhanced properties is also discussed. We believe that this work can optimize piezoelectric constant and dielectric loss simultaneously.
3. Results and discussions The XRD patterns of the ceramics with 2θ = 20–70° are shown in Fig. 1(a), and partial enlarged drawings of 2θ = 30–33° are also exhibited in Fig. 1(b) to identify phase accurately. The XRD patterns confirm that all the ceramics are pure perovskite phases without secondary phases, indicating that Ce and MnO2 are diffused into BS-PTBZT matrix. According to our previous reports, the BS-PT-BZT ceramics possess the MPB of R-T phase boundary [22]. It is found from Fig. 1(b) that the phase structure of this work remains unchanged after introducing Ce and/or MnO2, and the R-T phase coexistence can be observed in all compositions. Fig. 2 shows the SEM photographs derived from the surfaces of the
2. Experimental section 1 mol% MnO2 modified 0.99(0.36BiScO3-0.64PbTi1-xCexO3)-0.01Bi (Zn0.5Ti0.5)O3 (BS-PTC-BZT-MnO2) ceramics (x = 0, 0.01, 0.015, 0.02, 0.025, 0.03, and 0.04) were prepared by the conventional solid-state process method. Starting raw materials including Bi2O3 (99%), Sc2O3 (99.99%), PbO (99%), TiO2 (99%), ZnO (99.9%), MnO2 (99.9%), and CeO2 (99.99%) were weighed according to their stoichiometric ratio. The excess 2 mol% Bi2O3 was added to compensate the evaporation of
Fig. 2. FE-SEM images of surfaces of BS-PTC-BZT-MnO2 ceramics with (a)–(e) different Ce contents, and (f) x = 0.02 Ce doped only. 2
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Fig. 3. Temperature-dependent (a) dielectric constant (ɛr) and (b) dielectric loss (tan δ) of Ce and/or MnO2 doped ceramics as a function of Ce contents, and the inset in (a) is TC against compositions.
Fig. 4. (a) Piezoelectric and (b) dielectric properties of Ce and/or MnO2 doped ceramics as a function of Ce contents.
between Mn and Ce during the substitution of Ti results in formation of less oxygen vacancies, leading to weaker assistance effect of mass transport. Eqs. (1)–(5) can represent the above process [26,27]. VO·· and ′ (A = Ce and Mn) present oxygen vacancies and defect-dipole ATi clusters, respectively. 3MnO2 → MnO + Mn2O3 + OO
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2CeO2 → Ce2O3 + 1/2OO
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Ce2 O3 + 2TiO2 → 2Ce′Ti +
V ⋅⋅O
+ 3OO
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Mn2 O3 + 2TiO2 → 2Mn′Ti + V ⋅⋅O + 3OO
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MnO + TiO2 → Mn′Ti + V ⋅⋅O + OO
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On the other hand, excessive oxides may not completely dissolve in the solutions, resulting in assemble at grain boundaries and then restraining the grain growth [8]. In summary, the Ce and MnO2 co-doped ceramics possess small grain sizes with dense structure and uniform distribution. The temperature dependence of dielectric properties of the samples is shown in Fig. 3, measured at f = 1 kHz and 25–500 °C. The ferroelectric-paraelectric phase transition with increasing temperatures is revealed by the appearance of dielectric maximum. Curie temperature (TC) can be gained from the temperature at the dielectric peak, and the curves of TC vs. compositions are also exhibited in the inset of Fig. 3(a). In Fig. 3(a), it is found that TC decreases monotonously from 431 °C to 385 °C with increasing Ce contents (x = 0.00 to x = 0.04). It is found from Fig. 3(b) that dielectric loss (tan δ) of all samples with different Ce contents shows a stable changing tendency with increasing
Fig. 5. Comparison of BS-PT-based ceramic systems against their d33 and tan δ.
samples. All the specimens own a dense microstructure and uniform grains distribution. We can find from Fig. 2(e) and (f) that the samples with MnO2/Ce possess a larger grain size of approximately 3.5–4 µm than those of co-doped ones. Similar results are also observed in previous Mn-modified BS-PT-based systems [8,24]. According to previous reports, the concentration of oxygen vacancies increases due to the Ti substitution for multi-valence ions (Mn or Ce), which promotes mass transport and further assists grain growth during sintering process [8]. However, it is found from Fig. 2(a)–(e) that the average grain size becomes much smaller of ~ 1 µm after the addition of Ce, which can be explained in two aspects. On the one hand, the competitive relationship 3
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Fig. 6. (a) P-E loops of the samples. (b) Pr and (c) Eint values as a function of compositions.
Fig. 7. (a) S-E curves as a function of compositions. (b) Relevant parameters in S-E loops. (c) Asymmetry factor γs vs. compositions.
tan δ of the samples with x = 0.02 is higher than those of co-doped ones, but is more stable with increasing temperatures. Therefore, the ceramics with Ce and MnO2 possess high TC and low tan δ. Piezoelectric and dielectric properties of Ce and/or MnO2-doped ceramics with different Ce contents are exhibited in Fig. 4, measured at f = 1 kHz and room temperature. In Fig. 4(a), It is found that d33 and kp firstly increase with increasing Ce contents and then decrease with further doping, reaching the maximum values (d33 = 360 pC/N and kp = 0.512) for x = 0.02. Besides, the samples with x = 0.02 Ce (without MnO2) possess better piezoelectric properties (d33 = 380 pC/N and kp = 0.525) than those of co-doped ones, indicating that MnO2 does harm to piezoelectric properties [6,8,24,25]. It is found from Fig. 4(b) that with increasing Ce contents, dielectric constant (ɛr) firstly increases (x = 0.00–0.02) and then decreases with continuous dopants (x = 0.02–0.04), reaching the optimum values (ɛr = 1324) for x = 0.02. As for tan δ, it keeps a low level (tan δ < 1.7%) with the increase of Ce (x = 0.00–0.04) [Fig. 4(b)]. tan δ of the samples with x = 0.02 Ce (without MnO2) is 1.85%, which is higher than those of codoped samples, indicating that MnO2 can effectively reduce tan δ [6,8,24,25]. The optimized electrical property of d33 = 360 pC/N and
Fig. 8. Physical model for reducing tan δ in this work, in which defects and oxygen vacancies are amplified to clarify the process more clearly.
temperatures. As shown in the insert chart of Fig. 3(b), the Ce and MnO2 co-modified samples exhibit a lower tan δ than those of Mnmodified ones, indicating that Ce can usefully decrease tan δ. In addition, lower tan δ will be observed when more Ti is replaced by Ce. In addition, the temperature dependence of tan δ with x = 0.02 Ce (without MnO2) is also shown in the inset of Fig. 3(b). It is found that
Fig. 9. (a) d33 of the samples after annealing at various temperatures. (b) Curves of Td and TC against compositions. 4
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tan δ = 1.36% is observed at x = 0.02. This result indicates that Ce can suppress the deterioration of piezoelectric properties and keeps a stable low tan δ simultaneously. In addition, combined with SEM images [Fig. 2], we find that small grains are useful to enhance piezoelectric and dielectric properties in co-doped samples, while large grains are bad to the enhancement of electrical properties [24]. To evaluate the advance of this work, the statistics including d33 and tan δ [6,8,23,24,28,29] are gathered in Fig. 5. Higher d33 together with low tan δ can be achieved in this work. We realize the target of high d33 (d33 = 360 pC/N) and low tan δ (tan δ = 1.36%) simultaneously. As a result, the comprehensive properties in this work are superior to most previous reports of BS-PT-based ceramics. Fig. 6(a) shows the room-temperature polarization hysteresis loops (P-E) of the ceramics. We can find from Fig. 6(a) that all P-E loops are saturated but asymmetric, demonstrating the existence of internal bias field (Eint) [6,8,24]. It is found from Fig. 6(b) that the remnant polarization (Pr) initially decreases from 36.9 µC/cm2 (x = 0.00) to 35.1 µC/ cm2 (x = 0.02), which may result from the pinning of domain walls caused by the defects and oxygen vacancies produced by Ce and the acceptor type substitution of Ti for Ce in the lattice [24]. When further doping Ce from x = 0.02 to x = 0.04, Pr increases to 38.7 µC/cm2, resulting from the production of more oxygen vacancies induced by excessive addition of Ce. Combined with SEM images [Fig. 2], we find that large grains enhance ferroelectric properties, while small grains are harmful to electrical properties [6,23]. Eint values can be calculated by the Eq. (6) and shown in Fig. 6(c).
Eint = (E+ − E−)/2
chemical reaction [Eqs. (1)–(5)], compositing with matrix well and lowering the overall energy of the ceramics, which leads to the pinning of the 180° domain motions, finally reduce tan δ effectively. Fig. 9 shows the thermal stability of d33 in all the ceramics. It is found from Fig. 9(a) that d33 is stable with increasing temperatures initially and then rapidly drops to zero when the temperature approaches to TC. Depolarization temperature (Td) can be derived from the mutational point in curves of d33 vs. temperature. Although the temperature stability of d33 decreases slightly with increasing Ce contents, their d33 still keeps stable up to more than 350 °C, which is superior to PZT [1,6–8]. Fig. 9(b) presents the Td and TC vs. compositions of the ceramics. Similar changing trend of Td and TC indicates a good thermal stability of BS-PTC-BZT-MnO2 ceramics. 4. Conclusion We realize the excellent comprehensive properties (d33 = 360 pC/N and tan δ = 1.36%) in BS-PTC-BZT-MnO2 ceramics (MPB of R-T phase coexistence) with high TC of 422 °C by adding MnO2 and refining Ce contents. Partially replacing Ti with Ce can achieve a low dielectric loss and suppress the decrease of piezoelectric constant simultaneously. In addition, the temperature-dependent piezoelectric and dielectric properties are stable in a wide temperature range. Asymmetric P-E and S-E loops confirm the existence of defects and oxygen vacancies induced by Ce and Mn, which reduce dielectric loss effectively. We believe that BSPTC-BZT-MnO2 system can be well applied to high-temperature piezoelectric fields as power electronic devices.
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The initial increase of Eint from x = 0.00 to x = 0.02 is attributed to the space charges produced by the addition of Ce [8,24]. Then the decrease of Eint with further doping may be due to the competitive relation between Ce and Mn. Mn4+ and Ti4+ possess the similar ionic radius (0.0645 nm and 0.0605 nm, respectively), while much larger radius of Ce4+ (0.087 nm) makes it difficult for Ce4+ to occupy the sites of Ti4+. Moreover, the Eint of the compositions with x = 0.02 (without MnO2) (Eint = 2.15 kV/cm) plus the Eint of x = 0.00 (without Ce) (Eint = 2.0 kV/cm) is much larger than those of co-doped component (Eint = 2.32 kV/cm), further confirming the competitive relationship of the Ti substitution for multi-valence elements (Ce and Mn). As a result, the ceramics possess large Pr, and the existence of Eint confirms the existence of defects and oxygen vacancies induced by Ce and Mn, which helps reduce tan δ, as discussed above. Room-temperature strain loops (S-E) of all the samples are shown in Fig. 7(a). Butterfly-shaped loops can be observed in all compositions. However, all curves behave asymmetric, further implying the existence of Eint and the formation of defects and oxygen vacancies [8]. In addition, with increasing Ce contents from x = 0.00 to x = 0.02, S-E curves become more and more asymmetric, and then the degree of asymmetry becomes smaller with further doping. According to previous reports, any asymmetry in S-E loops can be expressed by an asymmetry factor γs, defined by the Eq. (7) [30]. Relevant parameters are shown in Fig. 7(b).
γs = (ΔS+ − ΔS −)/(ΔS+ + ΔS −)
Acknowledgement Authors gratefully acknowledge the supports of the National Science Foundation of China (NSFC Nos. 51722208 and 51472169). We also appreciate Wang Hui from the Analytical & Testing Center of Sichuan University for her help with SEM characterization. References [1] J.G. Chen, H.D. Shi, G.X. Liu, J.R. Cheng, S.X. Dong, Temperature dependence of dielectric, piezoelectric and elastic properties of BiScO3-PbTiO3 high temperature ceramics with morphotropic phase boundary (MPB) composition, J. Alloy. Compd. 537 (1) (2012) 280–285. [2] A.H. Qureshi, G. Shabbir, D.A. Hall, On the synthesis and dielectric studies of (1-x) Bi(Mg1/2Zr1/2)O3-xPbTiO3 piezoelectric ceramic system, Mater. Lett. 61 (23) (2007) 4482–4484. [3] J.G. Chen, J.R. Cheng, Enhanced thermal stability of lead-free high temperature 0.75BiFeO3−0.25BaTiO3 ceramics with excess Bi content, J. Alloy. Compd. 589 (9) (2014) 115–119. [4] Z.H. Yao, C.B. Xu, Z.J. Wang, Z. Song, Y.M. Zhang, W. Hu, H. Hao, M.H. Cao, H.X. Liu, Microstructure, ferro-piezoelectric and thermal stability of SiO2 modified BiFeO3-BaTiO3 high temperature piezoceramics, J. Mater. Sci. 26 (1) (2015) 479–484. [5] K. Yamakawa, K. Imai, O. Arisumi, T. Arikado, M. Yoshioka, T. Owada, K.O. kumura, Novel Pb(Ti, Zr)O3 (PZT) crystallization technique using flash lamp for ferroelectric RAM (FeRAM) embedded LSIs and one transistor type FeRAM devices, Jpn. J. Appl. Phys. 41 (4) (2002) 2630–2634. [6] J.G. Chen, Y.J. Dong, J.R. Cheng, Reduced dielectric loss and strain hysteresis in (0.97-x)BiScO3-xPbTiO3−0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceram. Int. 41 (8) (2015) 9828–9833. [7] Z. Gubinyi, C. Batur, A. Sayir, F. Dynys, Electrical properties of PZT piezoelectric ceramic at high temperatures, J. Electroceram. 20 (2) (2008) 95–105. [8] J.G. Chen, G.X. Jin, C.M. Wang, J.R. Cheng, Reduced dielectric loss and strain hysteresis in Fe and Mn comodified high-temperature BiScO3-PbTiO3 ceramics, J. Am. Ceram. Soc. 97 (12) (2014) 3890–3896. [9] J.G. Wu, Z. Fan, D.Q. Xiao, J.G. Zhu, J. Wang, Multiferroic bismuth ferrite-based materials for multifunctional applications: ceramic bulks, thin films and nanostructures, Prog. Mater. Sci. 84 (2016) 335–402. [10] J.G. Wu, D.Q. Xiao, J.G. Zhu, Potassium-sodium niobate lead-free piezoelectric materials: past, present, and future of phase boundaries, Chem. Rev. 115 (7) (2015) 2559–2595. [11] Y.Y. Wang, L. Hu, Q.L. Zhang, H. Yang, Phase transition characteristics and associated piezoelectricity of potassium-sodium niobate lead-free ceramics, Dalton Trans. 44 (30) (2015) 13688–13699. [12] H. Tian, C.P. Hu, X.D. Meng, Z.X. Zhou, G. Shi, Dielectric, piezoelectric, and elastic properties of K0.8Na0.2NbO3 single crystals, J. Mater. Chem. C 3 (37) (2015)
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It is found from Fig. 7(c) that γs firstly increases and then decreases with further doping, reaching the maximum value for x = 0.02. This result is accordance with the variation of Eint [Fig. 6(c)], also confirming the production of defects and oxygen vacancies, which can reduce tan δ. Besides, the ceramics with x = 0.02 (without MnO2) possess much lower γs than those of co-doped samples, indicating that the co-doped ceramics possess more defects and oxygen vacancies, and then tan δ can be further reduced [Fig. 4(b)]. Based on the evidences of existence of defects and oxygen vacancies, a detailed physical model for reducing tan δ is supplied, as shown in Fig. 8. Multi-valence elements (Ce and Mn) diffuse into BS-PT-BZT matrix, and defects and oxygen vacancies are produced after complex 5
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9609–9614. [13] J. Chen, J. Yuan, S.M. Bao, Y.J. Wu, G. Liu, Q. Chen, D.Q. Xiao, J.G. Zhu, Effects of (Li, Ce, Y) co-substitution on the properties of CaBi2Nb2O9 high temperature piezoceramics, Ceram. Int. 6 (43) (2017) 5002–5006. [14] X.D. Zhang, H.X. Yan, R.M.J. Reece, Effect of A site substitution on the properties of CaBi2Nb2O9 ferroelectric ceramics, J. Am. Ceram. Soc. 91 (9) (2010) 2928–2932. [15] Z.H. Peng, Q. Chen, Y.D. Wang, D.Q. Xin, D.Q. Xiao, J.G. Zhu, Enhancement of piezoelectric properties of (LiCePr)-multidoped CaBi2Nb2O9 high temperature ceramics, Mater. Lett. 15 (107) (2013) 14–16. [16] R.E. Eitel, C.A. Randall, T.R. Shrout, P.W. Rehring, W. Hackenberger, S.E. Park, New high temperature morphotropic phase boundary piezoelectrics based on Bi (Me)O3-PbTiO3 ceramics, Jpn. J. Appl. Phys. 40 (10) (2014) 5999–6002. [17] C.A. Randall, R. Eitel, B. Jones, T.R. Shrout, D.I. Woodward, I.M. Reaney, Investigation of a high TC piezoelectric system: (1-x)Bi(Mg1/2Ti1/2)O3-xPbTiO3, J. Appl. Phys. 95 (7) (2004) 3633–3639. [18] M.R. Suchomel, P.K. Davies, Predicting the position of the morphotropic phase boundary in high temperature PbTiO3-Bi(B′B”)O3 based dielectric ceramics, J. Appl. Phys. 96 (8) (2004) 4405–4410. [19] R.E. Eitel, C.A. Randall, T.R. Shrout, S.E. Park, Preparation and characterization of high temperature perovskite ferroelectrics in the solid solution (1-x)BiScO3xPbTiO3, Jpn. J. Appl. Phys. 41 (4A) (2002) 2099–2104. [20] I. Sterianou, I.M. Reaney, D.C. Sinclair, D.I. Woodward, High-temperature (1-x) BiSc1/2Fe1/2O3-xPbTiO3 piezoelectric ceramics, Appl. Phys. Lett. 87 (24) (2005) 299. [21] Z.H. Liu, A.R. Paterson, H. Wu, P. Gao, W. Ren, Z.G. Ye, Synthesis, structure and
[22]
[23]
[24]
[25] [26] [27] [28]
[29]
[30]
6
piezo-/ferroelectric properties of novel bismuth-containing ternary complex perovskite solid solution, J. Mater. Chem. C 5 (16) (2017) 3916–3923. Z. Liu, C.L. Zhao, J.F. Li, K. Wang, J.G. Wu, Large strain and temperature-insensitive piezoelectric effect in high-temperature piezoelectric ceramics, J. Mater. Chem. C 6 (3) (2018) 456–463. Q.W. Liao, X.S. Chen, X.C. Chu, F. Zeng, D. Guo, Effect of Fe doping on the structure and electric properties of relaxor type BSPT-PZN piezoelectric ceramics near the morphotropic phase boundary, Sens. Actuators A-Phys. 201 (10) (2013) 222–229. J.G. Chen, Z.Q. Hu, H.D. Shi, M.Y. Li, S.X. Dong, High-power piezoelectric characteristics of manganese-modified BiScO3-PbTiO3 high-temperature piezoelectric ceramics, J. Phys. D: Appl. Phys. 45 (46) (2012) 465303. J. Ryu, S. Priya, C. Sakaki, K. Uchino, High power piezoelectric characteristics of BiScO3-PbTiO3-Pb(Mn1/3Nb2/3)O3, Jpn. J. Appl. Phys. 41 (41) (2002) 6040–6044. X.J. Cheng, Z.W. Li, J.G. Wu, Colossal permittivity in ceramics of TiO2 co-doped with niobium and trivalent cation, J. Mater. Chem. A 3 (11) (2015) 5805–5810. Z.W. Li, J.G. Wu, W.J. Wu, Composition dependence of colossal permittivity in (Sm0.5Ta0.5)xTi1-xO2 ceramics, J. Mater. Chem. C 3 (35) (2015) 9206–9216. T.Y. Ansell, D.P. Cann, Piezoelectric properties of the high temperature MPB xPbTiO3-(1-x)[BiScO3-Bi(Ni1/2Ti1/2)O3] composition, J. Electroceram. 31 (1) (2013) 159–167. T. Sebastian, I. Sterianou, D.C. Sinclair, A.J. Bell, D.A. Hall, I.M. Reaney, High temperature piezoelectric ceramics in the Bi(Mg1/2Ti1/2)O3-BiFeO3-BiScO3-PbTiO3 system, J. Electroceram. 25 (2) (2010) 130–134. N. Balke, D.C. Lupascu, T. Granzow, J. Rödel, Fatigue of lead zirconate titanate ceramics. I: unipolar and DC loading, J. Am. Ceram. Soc. 90 (4) (2007) 1081–1087.