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3)O3 piezoelectric ceramics
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Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3– 0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics Jianguo Chenn, Yingjie Dong, Jinrong Cheng School of Materials Science and Engineering, Shanghai University, Shanghai, 200444, PR China Received 6 March 2015; received in revised form 30 March 2015; accepted 10 April 2015
Abstract (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 (BS–PT–PMnN) ceramics were prepared by solid-state reaction method. X-ray diffraction analysis revealed that the morphotropic phase boundary (MPB) of BS–PT–PMnN ceramics located near x ¼ 0.58. The high Curie temperature (437 1C), large piezoelectric constant (300 pC/N), low dielectric loss (0.015) and small strain hysteresis (20%) were obtained for the MPB composition. Its dielectric loss and strain hysteresis were reduced down to one third and half those of pure BiScO3–PbTiO3 (BS–PT) ceramics, respectively. In addition, the maximum vibration velocity of the BS–PT–PMnN ceramics was 0.85 ms 1, much superior to those of BS–PT (0.15 ms 1) and modified PZT (0.4 ms 1) ceramics. These results indicated BS–PT–PMnN ceramics were promising candidates for high temperature piezoelectric applications. & 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: BiScO3–PbTiO3–Pb(Mn1/3Nb2/3)O3; High temperature piezoelectric ceramics; Dielectric loss; Strain hysteresis
1. Introduction Piezoelectric actuators have been widely used in adaptive optics, high resolution positioning stages, and micro-electromechanical systems because of their so many merits, such as capable of generating motion on the nanometer scale, compact, energy-saving, large driving and holding forces in small sizes, and silent nonmagnetic operations [1,2]. Recently, it is increasingly recognized that piezoelectric actuators that can function at ambient temperatures above 150 1C without external cooling could greatly benefit a variety of important applications, especially in the fields of automotive, aerospace, and energy production industries [3,4]. These performances require the piezoelectric materials possess high Curie temperature, large piezoelectric constant, low strain hysteresis and/or high mechanical quality factor. The commercial piezoelectric PZT ceramics possess excellent dielectric and piezoelectric properties. Unfortunately, their Curie temperatures are only about 300 1C, indicating that they may seriously depolarize above 150 1C [5]. n
Corresponding author. Tel./fax: þ 86 021 66138065. E-mail address: [email protected] (J. Chen).
BiScO3–PbTiO3 (BS–PT) solid solutions exhibited both high Curie temperature (TC ¼ 450 1C) and large piezoelectric constant (d33 ¼ 450 pC/N), showing potential piezoelectric applications working stably above 150 1C [6]. However, the mechanical quality factor Qm and dielectric loss tan δ of BS–PT ceramics are 28 and 4% (103 Hz), respectively, indicating that they may generate too much heat when they work under high or/and resonate frequency [7,8]. In addition, the strain hysteresis under high electric field (50 kV/cm) of BS–PT ceramics is as high as 50%, which is much larger than those of the commercial PZT based materials. The strain hysteresis of piezoelectric actuator made of BS–PT ceramics is obvious, especially under the temperature of 200 1C, which may affect the precision performance of piezoelectric actuators [3]. Introducing Mn, Fe and Pb(Mn1/3Nb2/3)O3 (PMnN) in the solid solution was proved to decrease the dielectric loss and increase the mechanical quality factor [9–11]. Among these modifications, adding 10 at% PMnN in the BS–PT solid solutions was able to enhance the mechanical quality factor up to 1000, and kept the Curie temperature at about 400 1C [11]. To our best knowledge, this is the highest mechanical quality factor value for BS–PT based solid solutions. However,
http://dx.doi.org/10.1016/j.ceramint.2015.04.056 0272-8842/& 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056
(200)
(112)
(121) (21-1)
(102) (201)
(0-12) (211)
(002) (200)
(111)
(110)
(011)
(001) (100)
Intensity (CSP)
(002)
J. Chen et al. / Ceramics International ] (]]]]) ]]]–]]]
2
x=0.62 x=0.60 x=0.59
20
30
40 2θ (o)
50
(200)
(012)
(200)
(-111)
(111)
(110)
(100)
x=0.56 x=0.54
(-110)
x=0.58
6044 45 46 2θ (o)
Fig. 1. XRD patterns of BS–PT–PMnN ceramics.
too much (10 at%) PMnN addition deteriorated its piezoelectric constant severely (from 460 down to 80 pC/N). Furthermore, little attention has been paid on the strain hysteresis properties of chemical modified BS–PT based ceramics. In this paper, to achieve high curie temperature, large piezoelectric constant, low dielectric loss and small strain hysteresis, small amount (3 at%) of PMnN was introduced in the BS–PT solid solutions, and their structure, and dielectric and piezoelectric properties were systematically studied, especially for their strain hysteresis and generated heat. 2. Experimental procedure Ceramic powders of (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/ (0.54rxr0.62) (BS–PT–PMnN) were prepared using a traditional solid-state reaction method. The starting materials were Bi2O3, Sc2O3, PbO, TiO2, MnCO3 and Nb2O5, which all were of purities greater than 99.9%. The raw powder mixture of MnCO3 and Nb2O5 was ball-milled in polyethylene jar for 24 h. The mixed slurry was dried and calcined at 1000 1C for 5 h for phase formation of Mn1/3Nb2/3O2 powders, which was ball milled again to obtain fine particles. The obtained Mn1/3Nb2/3O2 powders and Bi2O3, Sc2O3, PbO, and TiO2 were mixed and ball milled together. The mixtures were calcined at 750–800 1C for 4 h and then were milled for an additional 24 h to make powders fine and uniform. After that, the powders were pressed into pellets with a diameter of 12.5 mm and thickness of 1.5 mm under 120 MPa. The green compacts were embedded in the calcined powders of same composition and sinter in a covered crucible at 1040–1120 1C for 3 h. The crystalline phase of the sintered pellets was identified by a X-ray diffraction (XRD) technique using Cu kα radiation (X'PertPro Diffractometer, Philips, Netherlands). Surface microstructure was examined by scanning electron microscopy (SEM, S4800, Hitachi, Tokyo, Japan). The sintered pellets were polished down to 0.5 mm, and electroded with a post fire silver paste. For electric measurements, BS–PT–PMnN ceramics were poled in an oil bath under an electric field of 40 kV/cm at 120 1C for 30 min. Poled samples were aged for 24 h before conducting any electrical measurement. Dielectric properties as a function of temperature were measured in the frequency range from 103 Hz to 106 Hz using a computer controlled precision LCR meter (4294A, Agilent 3Nb2/3)O3
Technologies). The piezoelectric constant d33 was measured using a quasi-static piezoelectric meter (ZJ-3D, Institute of Acoustics, Beijing, China). The electromechanical coupling factor kp and mechanical quality factor Qm were calculated based on the resonance method using an impedance analyzer (4294A, Agilent Technologies). The vibration velocity v0 was measured using the kp model using laser doppler vibrometers (LV-S01, Sunny Instruments Singapore Pte. Ltd). The vibration level was the rms value of the vibration velocity v0, which is independent of the sample size at the mechanical resonance frequency. The temperature data of the BS–PT–PMnN ceramics was detected by infrared thermometers (Optris LS-LT, Germany). The temperature dependent electromechanical coupling factor kp was determined by attaching the poled specimens to a conductive jig placed in a furnace. The poled pellets were supported only by the silver wires fired on both surfaces. 3. Results and discussion Fig. 1 shows the XRD patterns of BS–PT–PMnN ceramics with different PT contents. BS–PT–PMnN ceramics are well crystallized, and exhibit single perovskite structure without clearly secondary phases. BS–PT–PMnN ceramics with the composition of PT ¼ 0.54 show typical rhombohedral phase. With the increase of PT content, (200) reflection peak near 2θ ¼ 451 splits into (002) and (200) peaks, indicating that a phase transition from rhombohedral (R) to tetragonal (T) phases takes place in solid solutions. This is one of the morphotropic phase boundary (MPB) characteristics. The composition clearly splitting of rhombohedral and tetragonal phases is found at PT content of 0.58. It was reported that the MPB composition of BS–PT ceramics is at PT content of 0.64, which means that introducing PMnN moves the MPB composition to bismuth-rich side [6]. Taking the XRD data, the lattice parameters were calculated. For the MPB composition, c/a ratio is 1.02, which is comparable to that of BS–PT ceramics with the composition near the MPB. Fig. 2(a)–(d) gives the SEM images derived from fresh fracture surfaces of BS–PT–PMnN ceramics. The grain size of BS–PT–PMnN with PT content of 0.54 is about 5 mm, and its grain distribution is uniform. With the increase of PT content, the grain size increases dramatically, and the grain distribution becomes non-uniform. The average grain size of BS–PT– PMnN ceramics with MPB composition is about 20 mm, much larger than those of BS–PT ceramics. Furthermore, some pores are found in the ceramics. Similar results had been observed in 10 at% PMnN modified BS–PT ceramics. The relative density of BS–PT–PMnN ceramics decreases from 95% down to 92% with the PT content. The decreased density may result from the enlarged c/a ratios. In addition, the fracture surface of BS–PT– PMnN ceramics with PT content of 0.6 and 0.62 look more transgranular rather along grain boundary indicating that the grain boundary has the similar strength as the inside grain. The Curie temperature TC, dielectric constant εr, dielectric loss tan δ, piezoelectric constant d33, mechanical quality factor Qm and electromechanical coupling factor kp of BS–PT–PMnN ceramics are shown in Table 1. The planar electromechanical
Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056
J. Chen et al. / Ceramics International ] (]]]]) ]]]–]]]
3
Fig. 2. (a)–(d) SEM images of fractured surfaces of BS–PT–PMnN ceramics.
Table 1 The dielectric, piezoelectric properties and Curie temperature of BS–PT– PMnN ceramics with reported BS–PT and PZT based ceramics. Material
TC (1C)
d33 (pC/ Qm N)
kp
tan δ εr (1 kHz) (1 kHz)
Reference
PZT-8 PZT-4 BS–PT BS–PT–Mn BS–PT– 10PMnN BS–PT– PZN–Fe This work x¼ 0.54 x¼ 0.56 x¼ 0.58 x¼ 0.59 x¼ 0.60 x¼ 0.62
300 328 447 428 400
225 289 441 254 80
0.51 0.58 0.58 0.47 0.2
1000 1300 1051 865 –
0.004 0.004 0.04 0.01 –
[15] [16] [6] [10] [12]
440
220
40 0.33 1350
0.015
[11]
417 429 437 443 451 456
185 214 300 285 256 189
1000 500 28 210 1000
70 110 200 240 300 320
0.36 0.38 0.41 0.39 0.37 0.28
598 640 710 668 611 563
0.37 0.26 0.015 0.012 0.01 0.009
coupling factor kp and mechanical quality factor Qm are calculated according to the following formula: 1 f ¼ 0:398 r þ 0:579 2 f a f r kp Qm ¼
f 2a 2πf r Rf C T ðf 2a f 2r Þ
ð1Þ
ð2Þ
where fr and fa are the resonance and antiresonance frequency, Rf is the resonant resistance, and CT is the capacitance measured at the frequency of 1 kHz [7]. The Curie temperature TC is determined by the temperature at the dielectric peak in the εr–T curves. Values of εr, d33 and kp show maximum at the PT content of 0.58. Combining the
XRD results and electric properties, it is conjectured that the MPB composition is at the PT content of 0.58. Values of εr (1 kHz), tan δ (1 kHz), Curie temperature TC, piezoelectric constant d33 and mechanical quality factor Qm for the composition x ¼ 0.58 were of 710, 0.015, 437 1C, 300 pC/N and 200, respectively. BS–PT–PMnN ceramics with the composition near MPB show low dielectric loss of 1 1.5%, about one third of BS–PT ceramics (MPB composition). The reduced dielectric loss had been also found in PMnN modified PZT based materials [12]. Introduction of PMnN in the BS–PT may create oxygen vacancies, which may cluster at the domain wall region and pin the polarization, leading to the decrease of dielectric loss. The piezoelectric constant and electromechanical coupling factor of BS–PT–PMnN ceramics are much larger than those of 10% PMnN modified BS–PT ceramics, comparable with the Fe and Mn separately doped BS–PT ceramics and little lower than those of BS–PT ceramics [9,10]. The mechanical quality factor of BS–PT–PMnN ceramics with tetragonal phase is about 300, which is 10 times higher than that of BS–PT ceramics, much larger than those of Mn and Fe doped BS–PT ceramics [8,10–11]. Although, the mechanical quality factor of BS–PT–PMnN ceramics is much smaller than those of traditional commercial “hard” PZT ceramics, their Curie temperature is about 150 1C higher than those [13–14]. The figure of merit (FOM) of commercial hard PZT materials, pure BS–PT ceramics, Mn modified BS–PT and BS–PT–PMnN ceramics as a function of Curie temperature is given in Fig. 3. For BS–PT–PMnN ceramics, FOM is not very sensitive to the PT content, which is about five times higher than that of pure BS–PT ceramics. Mn modified BS–PT and BS–PT–PMnN ceramics exhibit both high Curie temperature and large FOM value. In addition, Curie temperature of BS–PT–PMnN is higher than those of Mn modified BS–PT ceramics, and their FOM values are comparable. These data
Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056
J. Chen et al. / Ceramics International ] (]]]]) ]]]–]]]
4 6
30 @ 1Hz
2
Polarization (μC/cm )
PZT-8 PZT-4 5
10
0.36BS-0.64PTM
4
10
This work
BS-PT (MPB)
20 10 0 -10 -20
-30 -60
320 360 400 440 Curie temperature (oC)
-40
480
Fig. 3. Figure of merit as a function of Curie temperature various for piezoelectric materials.
imply that BS–PT–PMnN ceramics can be used at higher temperature than traditional commercial hard-type PZT and Mn modified BS–PT ceramics. Fig. 4(a) shows the P–E hysteresis loops of poled BS–PT– PMnN ceramics measured at room temperature. With the increase of PT content, the remnant polarization of BS–PT–PMnN ceramics with tetragonal phase decreases whereas the coercive field increases, which may be owing to the enhanced c/a ratio. Compared with pure BS–PT ceramics, values of remnant polarization of BS–PT–PMnN ceramics are smaller, and their coercive fields are much larger, which may result from the pinning of domain wall due to the introduction of PMnN. Further investigations reflect that the P–E loops of BS–PT–PMnN ceramics become asymmetric, implying that there is an internal bias electric field in the polycrystalline grains. This is another character of hard piezoelectric ceramics. The internal bias field Einter (2Ei ¼ E þ E ) may results from the space charges produced by the addition of PMnN in the solid solution [15]. As shown in Fig. 4(b), the internal bias field of BS–PT–PMnN ceramics is very sensitive to the phase structure. The internal bias field of BS–PT–PMnN ceramics with rhombohedral phase is only about 1 kV/cm, whereas it jumps to 9 kV/cm when the composition is tetragonal phase. This may be due to that the tetragonal phase possesses more stable domain configuration than rhombohedral one. The increased internal bias field may lead to the enhancement of the mechanical quality factor in BS–PT–PMnN ceramics. It is interesting that both the coercive field and internal electric field (for x¼ 0.6, Ec ¼ 32.4 kV/cm, Einter ¼ 7.5 kV/cm) are larger than those of “hard” type PZT-4 (Ec ¼ 14.2 kV/cm, Einter ¼ 3 kV/cm) and PZT-8 ceramics (Ec ¼ 19 kV/cm, Einter ¼ 7 kV/cm) [16]. Fig. 5(a) and (b) displays the vibration velocity vo as a function of the electric field (rms value) and the temperature rise as a function of vibration velocity of BS–PT–PMnN ceramics with MPB composition. For comparison, the according data of pure BS–PT ceramics are also given. It is observed that the vibration velocity of BS–PT–PMnN ceramics increases with the electric field initially, and then become nearly saturated with further increasing electric field. This saturation may be due to the decrease in mechanical quality
-20
0
20
40
60
Electric field (kV/cm) 10
40
Coercive field (kV/cm)
280
x = 0.56 x = 0.58 x = 0.60 x = 0.62
8
30
6 20 4 10
0 0.52
2
0.54
0.56
0.58
0.60
0.62
0 0.64
Internal bias field (kV/cm)
Figure of Merit (ε. ε.kij.Qm)
10
PT content, x mol Fig. 4. (a) P–E loops, (b) coercive and internal electric field of BS–PT–PMnN ceramics at 1 Hz.
factor Qm with increasing electric field above a critical vibration level, as well as heat generation. Under the electric field of 9 V/mm (rms value), the vibration velocity reaches up to about 0.85 m/s, which is about 5 times that of pure BS–PT ceramics (0.15) and 2.2 times that of the conventional “hard” PZT ceramics (0.40 m/s) [17]. As mentioned above, the coercive field and internal electric field of BS–PT–PMnN ceramics are much larger than “hard” PZT and pure BS–PT ceramics. This may lead to the fact that the decrease of the mechanical quality factor with the increase of electric field and temperature for BS–PT–PMnN ceramics is not as serious as those of “hard” PZT and pure BS–PT ceramics. As well known, the vibration velocity of piezoelectric materials is proportional to the mechanical quality factor [13]. As a result, larger vibration velocity is obtained in the BS–PT–PMnN ceramics. As shown in Fig. 5(b), the temperature rise of BS–PT–PMnN ceramics is much slower than that of pure BS–PT ceramics, reflecting that PMnN modification is an effect way to decrease the generated heat from BS–PT ceramics driven under resonance frequency. From the practical perspective, the maximum vibration velocity was defined as the vo which generates ΔT¼ 20 k. It is observed that the maximum vibration velocity of BS–PT–PMnN ceramics is near 0.85 m/s. Considering the Curie temperature (TC ¼ 437 1C), piezoelectric properties (d33 ¼ 300 pC/N) and maximum vibration velocity (vo ¼ 0.85 m/s), BS–PT–PMnN ceramics have potential for high temperature and high power piezoelectric device applications.
Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056
J. Chen et al. / Ceramics International ] (]]]]) ]]]–]]]
0.35 BS-PT (MPB composition) BS-PT-PMnN (x = 0.58)
1.2
Strain (%)
0.25
0.9 0.6 0.3
0.20 0.15 0.10 0.05 0.00 0
15
BS-PT (MPB composition) BS-PT-PMnN (x= 0.58)
Strain(%)
30
3 6 9 12 Electric Field ( Vrms /mm)
20
10
20 40 Electric field (kV/cm)
60
0.25
700
0.20
600
0.15
500
0.10
400
0.05
300 200
0.00 0.56 0.57 0.58 0.59 0.60 0.61 0.62 PT content, x mol
0 1.0
60
ð3Þ
where H is strain hysteresis, H Emax =2 is different strain values with rising and falling fields at half maximum electric field, and Smax is the strain at the maximum electric field [18]. The calculated strain hysteresis of BS–PT–PMnN ceramics is presented in Fig. 6(c). The strain hysteresis decreases with the increase of PT content monotonously, reflecting the reduction of domain switching with the enhanced tetragonal
40
20 10 0
PZT
30 x = 0.62
The unipolar strain curves and large-signal d33 value (calculated from the various slopes) of unipolar strain of BS–PT–PMnN ceramics are presented in Fig. 6(a) and (b). Clearly, both the strain and large-signal d33 value reach maximum at MPB composition, which are 0.217% and 480 pm/V, respectively. Strain in piezoelectric materials is related to two different microstructural mechanisms, i.e., the (inverse) piezoelectric effect and domain switching, both contributing significantly to the high field induced strain. It is found that the strain curves of BS–PT–PMnN ceramics with falling and rising electric fields do not coincide with each other, showing the hysteretic characteristic with electric fields, which may be due to the domain switching. The strain hysteresis is commonly evaluated by the following formula:
50
x = 0.60
Fig. 5. (a) Vibration velocity of BS–PT–PMnN ceramics as a function of applied electric field, (b) Temperature rise of BS–PT–PMnN ceramics as a function of vibration velocity.
x = 0.58
0.2 0.4 0.6 0.8 Vibration Velocity (m/s)
BS-PT
0.0
H Emax =2 ; Smax
large-signal d 33 (pm/v)
0.0 0
Temperature Rise (k)
BS-PT (MPB composition) x = 0.58 x = 0.60 x = 0.62
0.30
Strain hysteresis (%)
Vibration Velocity (m/s)
1.5
H¼
5
Materials
Fig. 6. (a) Unipolar strain curves, (b) large-signal d33 value (calculated from the electric field induced strain curves) and (c) strain hysteresis of BS–PT– PMnN ceramics at 1 Hz.
distortion. The strain hysteresis of BS–PT–PMnN ceramics is only about half that of pure BS–PT ceramics, and comparable to the PZT based ceramics [18]. The reduced strain hysteresis may be due to the domain pinning by introducing PMnN in the solid solutions. Fig. 7 presents the effect of thermal depoling on the piezoelectric properties of BS–PT–PMnN ceramics with tetragonal phase. The kp of BS–PT–PMnN ceramics keep stable with increasing temperature initially, and then tend to zero when the temperature is near the TC. The piezoelectric temperature stability of BS–PT–PMnN ceramics increases slightly with PT content. For the composition with PT content of 0.6, the kp are stable up to 420 1C, about 250 1C higher than that of PZT, and 100 1C higher than those of Mn and Fe separately modified BS–PT ceramics [9,10]. In addition, the
Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056
J. Chen et al. / Ceramics International ] (]]]]) ]]]–]]]
6
0.5 x=0.58 x=0.60 x=0.62
kp
0.4
0.3
0.2
0.1 0
100
200
300
400
500
Temperature (oC) Fig. 7. Effect of thermal depoling on planar electromechanicalcouple factor kp of BS–PT–PMnN ceramics with different Fe contents.
temperature coefficient of resonance frequency in the temperature range of 25–400 1C is about 230 ppm/1C, which is comparable to PMnN modified PZT ceramics [19]. These results indicate that BS–PT–PMnN ceramics have potential application in the field of ultrasonic piezoelectric actuators at higher temperature than other chemical modified BS–PT ceramics and traditional commercial “hard” type PZT ceramics. 4. Conclusions The dielectric and piezoelectric properties of 3 at% PMnN modified BS–PT ceramics were investigated and compared with those of pure BS–PT and commercial PZT ceramics. Both high Curie temperature and better electric (piezoelectric and dielectric) properties were obtained in the 3 at% PMnN modified BS–PT ceramics with MPB composition. The Curie temperature of 437 1C, piezoelectric constant of 300 pC/N, maximum vibration velocity of 0.85 m/s and strain hysteresis of 22% was achieved for the MPB composition. In addition, the piezoelectric properties are stable up to 400 1C, which is about 200 1C higher than those of PZT based ceramics. These data reflect that BS–PT–PMnN ceramics are competitive candidates for high temperature and high performance piezoelectric applications. Acknowledgments This work was supported by the National Natural Science Foundation of China (Grant no. 51302163) and the Innovational Foundation of Shanghai University (Grant. no. K. 10-0110-13-009). Authors are also thankful to Mr. Bo Lu for recording XRD patterns (Rigaku D\max 2200, Tokyo, Japan).
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Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056
CERAMICS INTERNATIONAL
Ceramics International ] (]]]]) ]]]–]]] www.elsevier.com/locate/ceramint
Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3– 0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics Jianguo Chenn, Yingjie Dong, Jinrong Cheng School of Materials Science and Engineering, Shanghai University, Shanghai, 200444, PR China Received 6 March 2015; received in revised form 30 March 2015; accepted 10 April 2015
Abstract (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 (BS–PT–PMnN) ceramics were prepared by solid-state reaction method. X-ray diffraction analysis revealed that the morphotropic phase boundary (MPB) of BS–PT–PMnN ceramics located near x ¼ 0.58. The high Curie temperature (437 1C), large piezoelectric constant (300 pC/N), low dielectric loss (0.015) and small strain hysteresis (20%) were obtained for the MPB composition. Its dielectric loss and strain hysteresis were reduced down to one third and half those of pure BiScO3–PbTiO3 (BS–PT) ceramics, respectively. In addition, the maximum vibration velocity of the BS–PT–PMnN ceramics was 0.85 ms 1, much superior to those of BS–PT (0.15 ms 1) and modified PZT (0.4 ms 1) ceramics. These results indicated BS–PT–PMnN ceramics were promising candidates for high temperature piezoelectric applications. & 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: BiScO3–PbTiO3–Pb(Mn1/3Nb2/3)O3; High temperature piezoelectric ceramics; Dielectric loss; Strain hysteresis
1. Introduction Piezoelectric actuators have been widely used in adaptive optics, high resolution positioning stages, and micro-electromechanical systems because of their so many merits, such as capable of generating motion on the nanometer scale, compact, energy-saving, large driving and holding forces in small sizes, and silent nonmagnetic operations [1,2]. Recently, it is increasingly recognized that piezoelectric actuators that can function at ambient temperatures above 150 1C without external cooling could greatly benefit a variety of important applications, especially in the fields of automotive, aerospace, and energy production industries [3,4]. These performances require the piezoelectric materials possess high Curie temperature, large piezoelectric constant, low strain hysteresis and/or high mechanical quality factor. The commercial piezoelectric PZT ceramics possess excellent dielectric and piezoelectric properties. Unfortunately, their Curie temperatures are only about 300 1C, indicating that they may seriously depolarize above 150 1C [5]. n
Corresponding author. Tel./fax: þ 86 021 66138065. E-mail address: [email protected] (J. Chen).
BiScO3–PbTiO3 (BS–PT) solid solutions exhibited both high Curie temperature (TC ¼ 450 1C) and large piezoelectric constant (d33 ¼ 450 pC/N), showing potential piezoelectric applications working stably above 150 1C [6]. However, the mechanical quality factor Qm and dielectric loss tan δ of BS–PT ceramics are 28 and 4% (103 Hz), respectively, indicating that they may generate too much heat when they work under high or/and resonate frequency [7,8]. In addition, the strain hysteresis under high electric field (50 kV/cm) of BS–PT ceramics is as high as 50%, which is much larger than those of the commercial PZT based materials. The strain hysteresis of piezoelectric actuator made of BS–PT ceramics is obvious, especially under the temperature of 200 1C, which may affect the precision performance of piezoelectric actuators [3]. Introducing Mn, Fe and Pb(Mn1/3Nb2/3)O3 (PMnN) in the solid solution was proved to decrease the dielectric loss and increase the mechanical quality factor [9–11]. Among these modifications, adding 10 at% PMnN in the BS–PT solid solutions was able to enhance the mechanical quality factor up to 1000, and kept the Curie temperature at about 400 1C [11]. To our best knowledge, this is the highest mechanical quality factor value for BS–PT based solid solutions. However,
http://dx.doi.org/10.1016/j.ceramint.2015.04.056 0272-8842/& 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056
(200)
(112)
(121) (21-1)
(102) (201)
(0-12) (211)
(002) (200)
(111)
(110)
(011)
(001) (100)
Intensity (CSP)
(002)
J. Chen et al. / Ceramics International ] (]]]]) ]]]–]]]
2
x=0.62 x=0.60 x=0.59
20
30
40 2θ (o)
50
(200)
(012)
(200)
(-111)
(111)
(110)
(100)
x=0.56 x=0.54
(-110)
x=0.58
6044 45 46 2θ (o)
Fig. 1. XRD patterns of BS–PT–PMnN ceramics.
too much (10 at%) PMnN addition deteriorated its piezoelectric constant severely (from 460 down to 80 pC/N). Furthermore, little attention has been paid on the strain hysteresis properties of chemical modified BS–PT based ceramics. In this paper, to achieve high curie temperature, large piezoelectric constant, low dielectric loss and small strain hysteresis, small amount (3 at%) of PMnN was introduced in the BS–PT solid solutions, and their structure, and dielectric and piezoelectric properties were systematically studied, especially for their strain hysteresis and generated heat. 2. Experimental procedure Ceramic powders of (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/ (0.54rxr0.62) (BS–PT–PMnN) were prepared using a traditional solid-state reaction method. The starting materials were Bi2O3, Sc2O3, PbO, TiO2, MnCO3 and Nb2O5, which all were of purities greater than 99.9%. The raw powder mixture of MnCO3 and Nb2O5 was ball-milled in polyethylene jar for 24 h. The mixed slurry was dried and calcined at 1000 1C for 5 h for phase formation of Mn1/3Nb2/3O2 powders, which was ball milled again to obtain fine particles. The obtained Mn1/3Nb2/3O2 powders and Bi2O3, Sc2O3, PbO, and TiO2 were mixed and ball milled together. The mixtures were calcined at 750–800 1C for 4 h and then were milled for an additional 24 h to make powders fine and uniform. After that, the powders were pressed into pellets with a diameter of 12.5 mm and thickness of 1.5 mm under 120 MPa. The green compacts were embedded in the calcined powders of same composition and sinter in a covered crucible at 1040–1120 1C for 3 h. The crystalline phase of the sintered pellets was identified by a X-ray diffraction (XRD) technique using Cu kα radiation (X'PertPro Diffractometer, Philips, Netherlands). Surface microstructure was examined by scanning electron microscopy (SEM, S4800, Hitachi, Tokyo, Japan). The sintered pellets were polished down to 0.5 mm, and electroded with a post fire silver paste. For electric measurements, BS–PT–PMnN ceramics were poled in an oil bath under an electric field of 40 kV/cm at 120 1C for 30 min. Poled samples were aged for 24 h before conducting any electrical measurement. Dielectric properties as a function of temperature were measured in the frequency range from 103 Hz to 106 Hz using a computer controlled precision LCR meter (4294A, Agilent 3Nb2/3)O3
Technologies). The piezoelectric constant d33 was measured using a quasi-static piezoelectric meter (ZJ-3D, Institute of Acoustics, Beijing, China). The electromechanical coupling factor kp and mechanical quality factor Qm were calculated based on the resonance method using an impedance analyzer (4294A, Agilent Technologies). The vibration velocity v0 was measured using the kp model using laser doppler vibrometers (LV-S01, Sunny Instruments Singapore Pte. Ltd). The vibration level was the rms value of the vibration velocity v0, which is independent of the sample size at the mechanical resonance frequency. The temperature data of the BS–PT–PMnN ceramics was detected by infrared thermometers (Optris LS-LT, Germany). The temperature dependent electromechanical coupling factor kp was determined by attaching the poled specimens to a conductive jig placed in a furnace. The poled pellets were supported only by the silver wires fired on both surfaces. 3. Results and discussion Fig. 1 shows the XRD patterns of BS–PT–PMnN ceramics with different PT contents. BS–PT–PMnN ceramics are well crystallized, and exhibit single perovskite structure without clearly secondary phases. BS–PT–PMnN ceramics with the composition of PT ¼ 0.54 show typical rhombohedral phase. With the increase of PT content, (200) reflection peak near 2θ ¼ 451 splits into (002) and (200) peaks, indicating that a phase transition from rhombohedral (R) to tetragonal (T) phases takes place in solid solutions. This is one of the morphotropic phase boundary (MPB) characteristics. The composition clearly splitting of rhombohedral and tetragonal phases is found at PT content of 0.58. It was reported that the MPB composition of BS–PT ceramics is at PT content of 0.64, which means that introducing PMnN moves the MPB composition to bismuth-rich side [6]. Taking the XRD data, the lattice parameters were calculated. For the MPB composition, c/a ratio is 1.02, which is comparable to that of BS–PT ceramics with the composition near the MPB. Fig. 2(a)–(d) gives the SEM images derived from fresh fracture surfaces of BS–PT–PMnN ceramics. The grain size of BS–PT–PMnN with PT content of 0.54 is about 5 mm, and its grain distribution is uniform. With the increase of PT content, the grain size increases dramatically, and the grain distribution becomes non-uniform. The average grain size of BS–PT– PMnN ceramics with MPB composition is about 20 mm, much larger than those of BS–PT ceramics. Furthermore, some pores are found in the ceramics. Similar results had been observed in 10 at% PMnN modified BS–PT ceramics. The relative density of BS–PT–PMnN ceramics decreases from 95% down to 92% with the PT content. The decreased density may result from the enlarged c/a ratios. In addition, the fracture surface of BS–PT– PMnN ceramics with PT content of 0.6 and 0.62 look more transgranular rather along grain boundary indicating that the grain boundary has the similar strength as the inside grain. The Curie temperature TC, dielectric constant εr, dielectric loss tan δ, piezoelectric constant d33, mechanical quality factor Qm and electromechanical coupling factor kp of BS–PT–PMnN ceramics are shown in Table 1. The planar electromechanical
Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056
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3
Fig. 2. (a)–(d) SEM images of fractured surfaces of BS–PT–PMnN ceramics.
Table 1 The dielectric, piezoelectric properties and Curie temperature of BS–PT– PMnN ceramics with reported BS–PT and PZT based ceramics. Material
TC (1C)
d33 (pC/ Qm N)
kp
tan δ εr (1 kHz) (1 kHz)
Reference
PZT-8 PZT-4 BS–PT BS–PT–Mn BS–PT– 10PMnN BS–PT– PZN–Fe This work x¼ 0.54 x¼ 0.56 x¼ 0.58 x¼ 0.59 x¼ 0.60 x¼ 0.62
300 328 447 428 400
225 289 441 254 80
0.51 0.58 0.58 0.47 0.2
1000 1300 1051 865 –
0.004 0.004 0.04 0.01 –
[15] [16] [6] [10] [12]
440
220
40 0.33 1350
0.015
[11]
417 429 437 443 451 456
185 214 300 285 256 189
1000 500 28 210 1000
70 110 200 240 300 320
0.36 0.38 0.41 0.39 0.37 0.28
598 640 710 668 611 563
0.37 0.26 0.015 0.012 0.01 0.009
coupling factor kp and mechanical quality factor Qm are calculated according to the following formula: 1 f ¼ 0:398 r þ 0:579 2 f a f r kp Qm ¼
f 2a 2πf r Rf C T ðf 2a f 2r Þ
ð1Þ
ð2Þ
where fr and fa are the resonance and antiresonance frequency, Rf is the resonant resistance, and CT is the capacitance measured at the frequency of 1 kHz [7]. The Curie temperature TC is determined by the temperature at the dielectric peak in the εr–T curves. Values of εr, d33 and kp show maximum at the PT content of 0.58. Combining the
XRD results and electric properties, it is conjectured that the MPB composition is at the PT content of 0.58. Values of εr (1 kHz), tan δ (1 kHz), Curie temperature TC, piezoelectric constant d33 and mechanical quality factor Qm for the composition x ¼ 0.58 were of 710, 0.015, 437 1C, 300 pC/N and 200, respectively. BS–PT–PMnN ceramics with the composition near MPB show low dielectric loss of 1 1.5%, about one third of BS–PT ceramics (MPB composition). The reduced dielectric loss had been also found in PMnN modified PZT based materials [12]. Introduction of PMnN in the BS–PT may create oxygen vacancies, which may cluster at the domain wall region and pin the polarization, leading to the decrease of dielectric loss. The piezoelectric constant and electromechanical coupling factor of BS–PT–PMnN ceramics are much larger than those of 10% PMnN modified BS–PT ceramics, comparable with the Fe and Mn separately doped BS–PT ceramics and little lower than those of BS–PT ceramics [9,10]. The mechanical quality factor of BS–PT–PMnN ceramics with tetragonal phase is about 300, which is 10 times higher than that of BS–PT ceramics, much larger than those of Mn and Fe doped BS–PT ceramics [8,10–11]. Although, the mechanical quality factor of BS–PT–PMnN ceramics is much smaller than those of traditional commercial “hard” PZT ceramics, their Curie temperature is about 150 1C higher than those [13–14]. The figure of merit (FOM) of commercial hard PZT materials, pure BS–PT ceramics, Mn modified BS–PT and BS–PT–PMnN ceramics as a function of Curie temperature is given in Fig. 3. For BS–PT–PMnN ceramics, FOM is not very sensitive to the PT content, which is about five times higher than that of pure BS–PT ceramics. Mn modified BS–PT and BS–PT–PMnN ceramics exhibit both high Curie temperature and large FOM value. In addition, Curie temperature of BS–PT–PMnN is higher than those of Mn modified BS–PT ceramics, and their FOM values are comparable. These data
Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056
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4 6
30 @ 1Hz
2
Polarization (μC/cm )
PZT-8 PZT-4 5
10
0.36BS-0.64PTM
4
10
This work
BS-PT (MPB)
20 10 0 -10 -20
-30 -60
320 360 400 440 Curie temperature (oC)
-40
480
Fig. 3. Figure of merit as a function of Curie temperature various for piezoelectric materials.
imply that BS–PT–PMnN ceramics can be used at higher temperature than traditional commercial hard-type PZT and Mn modified BS–PT ceramics. Fig. 4(a) shows the P–E hysteresis loops of poled BS–PT– PMnN ceramics measured at room temperature. With the increase of PT content, the remnant polarization of BS–PT–PMnN ceramics with tetragonal phase decreases whereas the coercive field increases, which may be owing to the enhanced c/a ratio. Compared with pure BS–PT ceramics, values of remnant polarization of BS–PT–PMnN ceramics are smaller, and their coercive fields are much larger, which may result from the pinning of domain wall due to the introduction of PMnN. Further investigations reflect that the P–E loops of BS–PT–PMnN ceramics become asymmetric, implying that there is an internal bias electric field in the polycrystalline grains. This is another character of hard piezoelectric ceramics. The internal bias field Einter (2Ei ¼ E þ E ) may results from the space charges produced by the addition of PMnN in the solid solution [15]. As shown in Fig. 4(b), the internal bias field of BS–PT–PMnN ceramics is very sensitive to the phase structure. The internal bias field of BS–PT–PMnN ceramics with rhombohedral phase is only about 1 kV/cm, whereas it jumps to 9 kV/cm when the composition is tetragonal phase. This may be due to that the tetragonal phase possesses more stable domain configuration than rhombohedral one. The increased internal bias field may lead to the enhancement of the mechanical quality factor in BS–PT–PMnN ceramics. It is interesting that both the coercive field and internal electric field (for x¼ 0.6, Ec ¼ 32.4 kV/cm, Einter ¼ 7.5 kV/cm) are larger than those of “hard” type PZT-4 (Ec ¼ 14.2 kV/cm, Einter ¼ 3 kV/cm) and PZT-8 ceramics (Ec ¼ 19 kV/cm, Einter ¼ 7 kV/cm) [16]. Fig. 5(a) and (b) displays the vibration velocity vo as a function of the electric field (rms value) and the temperature rise as a function of vibration velocity of BS–PT–PMnN ceramics with MPB composition. For comparison, the according data of pure BS–PT ceramics are also given. It is observed that the vibration velocity of BS–PT–PMnN ceramics increases with the electric field initially, and then become nearly saturated with further increasing electric field. This saturation may be due to the decrease in mechanical quality
-20
0
20
40
60
Electric field (kV/cm) 10
40
Coercive field (kV/cm)
280
x = 0.56 x = 0.58 x = 0.60 x = 0.62
8
30
6 20 4 10
0 0.52
2
0.54
0.56
0.58
0.60
0.62
0 0.64
Internal bias field (kV/cm)
Figure of Merit (ε. ε.kij.Qm)
10
PT content, x mol Fig. 4. (a) P–E loops, (b) coercive and internal electric field of BS–PT–PMnN ceramics at 1 Hz.
factor Qm with increasing electric field above a critical vibration level, as well as heat generation. Under the electric field of 9 V/mm (rms value), the vibration velocity reaches up to about 0.85 m/s, which is about 5 times that of pure BS–PT ceramics (0.15) and 2.2 times that of the conventional “hard” PZT ceramics (0.40 m/s) [17]. As mentioned above, the coercive field and internal electric field of BS–PT–PMnN ceramics are much larger than “hard” PZT and pure BS–PT ceramics. This may lead to the fact that the decrease of the mechanical quality factor with the increase of electric field and temperature for BS–PT–PMnN ceramics is not as serious as those of “hard” PZT and pure BS–PT ceramics. As well known, the vibration velocity of piezoelectric materials is proportional to the mechanical quality factor [13]. As a result, larger vibration velocity is obtained in the BS–PT–PMnN ceramics. As shown in Fig. 5(b), the temperature rise of BS–PT–PMnN ceramics is much slower than that of pure BS–PT ceramics, reflecting that PMnN modification is an effect way to decrease the generated heat from BS–PT ceramics driven under resonance frequency. From the practical perspective, the maximum vibration velocity was defined as the vo which generates ΔT¼ 20 k. It is observed that the maximum vibration velocity of BS–PT–PMnN ceramics is near 0.85 m/s. Considering the Curie temperature (TC ¼ 437 1C), piezoelectric properties (d33 ¼ 300 pC/N) and maximum vibration velocity (vo ¼ 0.85 m/s), BS–PT–PMnN ceramics have potential for high temperature and high power piezoelectric device applications.
Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056
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0.35 BS-PT (MPB composition) BS-PT-PMnN (x = 0.58)
1.2
Strain (%)
0.25
0.9 0.6 0.3
0.20 0.15 0.10 0.05 0.00 0
15
BS-PT (MPB composition) BS-PT-PMnN (x= 0.58)
Strain(%)
30
3 6 9 12 Electric Field ( Vrms /mm)
20
10
20 40 Electric field (kV/cm)
60
0.25
700
0.20
600
0.15
500
0.10
400
0.05
300 200
0.00 0.56 0.57 0.58 0.59 0.60 0.61 0.62 PT content, x mol
0 1.0
60
ð3Þ
where H is strain hysteresis, H Emax =2 is different strain values with rising and falling fields at half maximum electric field, and Smax is the strain at the maximum electric field [18]. The calculated strain hysteresis of BS–PT–PMnN ceramics is presented in Fig. 6(c). The strain hysteresis decreases with the increase of PT content monotonously, reflecting the reduction of domain switching with the enhanced tetragonal
40
20 10 0
PZT
30 x = 0.62
The unipolar strain curves and large-signal d33 value (calculated from the various slopes) of unipolar strain of BS–PT–PMnN ceramics are presented in Fig. 6(a) and (b). Clearly, both the strain and large-signal d33 value reach maximum at MPB composition, which are 0.217% and 480 pm/V, respectively. Strain in piezoelectric materials is related to two different microstructural mechanisms, i.e., the (inverse) piezoelectric effect and domain switching, both contributing significantly to the high field induced strain. It is found that the strain curves of BS–PT–PMnN ceramics with falling and rising electric fields do not coincide with each other, showing the hysteretic characteristic with electric fields, which may be due to the domain switching. The strain hysteresis is commonly evaluated by the following formula:
50
x = 0.60
Fig. 5. (a) Vibration velocity of BS–PT–PMnN ceramics as a function of applied electric field, (b) Temperature rise of BS–PT–PMnN ceramics as a function of vibration velocity.
x = 0.58
0.2 0.4 0.6 0.8 Vibration Velocity (m/s)
BS-PT
0.0
H Emax =2 ; Smax
large-signal d 33 (pm/v)
0.0 0
Temperature Rise (k)
BS-PT (MPB composition) x = 0.58 x = 0.60 x = 0.62
0.30
Strain hysteresis (%)
Vibration Velocity (m/s)
1.5
H¼
5
Materials
Fig. 6. (a) Unipolar strain curves, (b) large-signal d33 value (calculated from the electric field induced strain curves) and (c) strain hysteresis of BS–PT– PMnN ceramics at 1 Hz.
distortion. The strain hysteresis of BS–PT–PMnN ceramics is only about half that of pure BS–PT ceramics, and comparable to the PZT based ceramics [18]. The reduced strain hysteresis may be due to the domain pinning by introducing PMnN in the solid solutions. Fig. 7 presents the effect of thermal depoling on the piezoelectric properties of BS–PT–PMnN ceramics with tetragonal phase. The kp of BS–PT–PMnN ceramics keep stable with increasing temperature initially, and then tend to zero when the temperature is near the TC. The piezoelectric temperature stability of BS–PT–PMnN ceramics increases slightly with PT content. For the composition with PT content of 0.6, the kp are stable up to 420 1C, about 250 1C higher than that of PZT, and 100 1C higher than those of Mn and Fe separately modified BS–PT ceramics [9,10]. In addition, the
Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056
J. Chen et al. / Ceramics International ] (]]]]) ]]]–]]]
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Temperature (oC) Fig. 7. Effect of thermal depoling on planar electromechanicalcouple factor kp of BS–PT–PMnN ceramics with different Fe contents.
temperature coefficient of resonance frequency in the temperature range of 25–400 1C is about 230 ppm/1C, which is comparable to PMnN modified PZT ceramics [19]. These results indicate that BS–PT–PMnN ceramics have potential application in the field of ultrasonic piezoelectric actuators at higher temperature than other chemical modified BS–PT ceramics and traditional commercial “hard” type PZT ceramics. 4. Conclusions The dielectric and piezoelectric properties of 3 at% PMnN modified BS–PT ceramics were investigated and compared with those of pure BS–PT and commercial PZT ceramics. Both high Curie temperature and better electric (piezoelectric and dielectric) properties were obtained in the 3 at% PMnN modified BS–PT ceramics with MPB composition. The Curie temperature of 437 1C, piezoelectric constant of 300 pC/N, maximum vibration velocity of 0.85 m/s and strain hysteresis of 22% was achieved for the MPB composition. In addition, the piezoelectric properties are stable up to 400 1C, which is about 200 1C higher than those of PZT based ceramics. These data reflect that BS–PT–PMnN ceramics are competitive candidates for high temperature and high performance piezoelectric applications. Acknowledgments This work was supported by the National Natural Science Foundation of China (Grant no. 51302163) and the Innovational Foundation of Shanghai University (Grant. no. K. 10-0110-13-009). Authors are also thankful to Mr. Bo Lu for recording XRD patterns (Rigaku D\max 2200, Tokyo, Japan).
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Please cite this article as: J. Chen, et al., Reduced dielectric loss and strain hysteresis in (0.97 x)BiScO3–xPbTiO3–0.03Pb(Mn1/3Nb2/3)O3 piezoelectric ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.056