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Article

Structural Evolution and Enhanced Piezoelectric Activity in Novel Lead-Free BaTiO3-Ca(Sn1/2Zr1/2)O3 Solid Solutions

by
Ke Zhang
1,
Pan Gao
1,*,
Chang Liu
2,*,
Xin Chen
1,
Xinye Huang
1,
Yongping Pu
2 and
Zenghui Liu
3,*
1
School of Electronic Information and Artificial Intelligence, Shaanxi University of Science and Technology, Xi’an 710021, China
2
School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an 710021, China
3
Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education & International Center for Dielectric Research, School of Electronic Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, China
*
Authors to whom correspondence should be addressed.
Energies 2022, 15(20), 7795; https://doi.org/10.3390/en15207795
Submission received: 25 September 2022 / Revised: 18 October 2022 / Accepted: 19 October 2022 / Published: 21 October 2022
(This article belongs to the Special Issue Advanced Materials for Energy Harvesting, Storage and Conversion)
Browse Figures
Versions Notes

Abstract

:
In this study, a series of solid solutions of (1−x)BaTiO3-xCa(Sn1/2Zr1/2)O3 (abbreviated as (1−x)BT-xCSZ, x = 0.00–0.15) ceramics have been prepared by the conventional solid-state reaction method to search for high performance lead-free piezoelectric materials. The structural evolution, microstructure, and piezoelectric properties are investigated. X-ray diffraction (XRD) results indicate that the phase symmetry strongly depends on the CSZ content. A tetragonal phase is well-maintained in the compositions of 0 ≤ x ≤ 0.03, and coexistence of tetragonal and cubic phases is obtained in the range of x = 0.06–0.09, beyond which a pure cubic phase becomes stable. More importantly, a significantly enhanced piezoelectric coefficient of d33 = 388 ± 9 pC/N is attained in the composition of x = 0.06 in the MPB region, where a tetragonal ferroelectric phase and an ergodic relaxor phase with average cubic symmetry coexist. Based on the analysis of crystal structure and dielectric properties, a temperature-composition phase diagram consisting of four phase regions is established. This study indicates that the lead-free BT-CSZ binary system has great potential for use in electromechanical transducer applications.

1. Introduction

Piezoelectric material is capable of converting mechanical energy into electrical energy, and vice versa. For a long time, considerable attention has been paid to Pb(Zr1−xTix)O3 (PZT) ceramics because of their admirable piezoelectric performance, which have been extensively utilized in actuating and sensing devices [1]. With the development of the electronics industry and growing environmental concerns, the use of toxic lead is restricted in many countries due to environmental and human health issues [2,3,4]. As a result, special attention has been paid to lead-free piezoelectric materials in order to replace the toxic PZT. Among the lead-free family, BaTiO3 (BT) ceramic is the first man-made piezoelectric material, but it shows a relatively low piezoelectric coefficient (d33) [5]. Subsequently, great efforts have been put into BT-based ceramics to optimize the piezoelectric properties; effective approaches are being explored, such as doping modification, microstructure design, domain engineering, mechanical imprint, and composite approach [6,7,8,9,10,11,12,13,14].
Among these methods, chemical doping on the perovskite A-site and B-site of BT ceramics to construct a multiphase boundary is particularly effective to obtain better piezoelectric properties. It is well-known that the enhanced piezoelectric responses in PZT are attributed to the morphotropic phase boundary (MPB), where different phases (such as rhombohedral, tetragonal, and monoclinic) coexist. The phase coexistence is believed to facilitate the polarization rotation among these phases, leading to an enhancement of piezoelectric properties [15,16]. Similarly, an enhanced piezoelectric coefficient (d33) has been observed in chemically modified BT-based ceramics by forming a phase boundary, which is comparable to that of PZT ceramics, triggering extensive studies on BT-based lead-free piezoelectric materials [17,18,19,20,21,22,23].
The construction of a phase boundary can be realized by optimizing the phase transition temperatures of BT-based ceramics, i.e., the rhombohedral-orthorhombic, orthorhombic-tetragonal, and tetragonal-cubic phase transition temperatures (TR-O, TO-T, and TT-C). It has been shown that the phase transition temperatures can be tuned by replacing the A-site and/or B-site ions using isovalent elements, such as Ca, Zr, and Hf [24,25,26,27,28,29]. In particular, an enhanced piezoelectric property is expected when these phase transition temperatures become convergent at room temperature, where a phase boundary is formed near the triple point or quadruple compositions [30,31,32,33,34,35,36,37].
Although significant progress has been made in lead-free piezoelectric materials, their overall performances are still inferior to those of lead-based ones. Therefore, the objective of this study is to design novel lead-free piezoelectric materials with better piezoelectric properties. In this study, the replacement of Ca on the A-site and Zr/Sn on the B-site of the BT lattices has been performed to construct a phase boundary. A significantly enhanced piezoelectric property is found in the newly developed phase boundary, where the ferroelectric phase and the ergodic relaxor phase coexist.

2. Experimental Procedures

2.1. Materials Preparation

A series of the piezoceramics (1−x)BT-xCSZ with compositions x = 0–0.15 were fabricated by the conventional solid-state reaction route. Starting powders of barium carbonate (BaCO3, 99%), calcium carbonate (CaCO3, 99%), titanium dioxide (TiO2, 99%), zirconium dioxide (ZrO2, 99%), and stannic dioxide (SnO2, 99%) were used as raw materials. All the reagent-grade powders were thoroughly mixed in proportion and ball-milled for 4 h with stabilized zirconia beads and ethanol as the mixing medium. The mixed powders were dried and then put into a furnace and calcined at 800 °C for 3 h in a sealed Al2O3 crucible. The calcined powders were ball-milled again for 4 h for better homogenization and mixed with a 5 wt% polyvinyl alcohol (PVA) solution. (The PVA solution worked as a binder and 7 drops of that were added to 5 g (1−x)BT-xCSZ powders approximatively). Then, the dried slurries were shaped into pellets of 6 mm in diameter and ~2.0 mm in thickness under uniaxial dry pressing at 10 MPa. The final sintering of the bulk piezoceramics was carried out at 1280–1420 °C depending on their composition for 3 h in air to form dense ceramics.

2.2. Characterization

The density of the sintered (1−x)BT-xCSZ ceramics was measured by the Archimedes water immersion method. The crystal structure and phase evolution were identified by X-ray diffraction (XRD, PANalytical Empyrean diffractometer, Almelo, The Netherlands) with a Cu-Kα1 X-ray radiation. The lattice parameters were calculated by the Rietveld refinements using the Topas Academic software. After sputtering gold on the polished and thermally etched surface, the microstructure of the sintered samples was examined by scanning electron microscopy, (SEM, FEI, Verios 460, Hillsboro, OR, USA). To characterize the electrical properties, the studied ceramics were further polished to ~0.5 mm in thickness and covered with silver paste on both surfaces as electrodes. The permittivity and loss factor were measured under different frequencies using a computer-controlled programmable furnace with an LCR meter (Agilent, E4980A, Santa Clara, CA, USA) in the temperature range of 30 °C to 300 °C. The polarization-electric field (P-E) hysteresis loops were recorded at room temperature by a ferroelectric test system (TF Analyzer 2000, aixACCT, Aachen, Germany) at a frequency of 10 Hz. After poling under a DC electric field of 3 kV/mm at room temperature for 10 min, the piezoelectric coefficient d33 was measured using a quasi-static d33 testing meter (ZJ-3AN, CAS, Beijing, China).

3. Results and Discussion

3.1. Bulk Density

The relationship between the relative density of the (1−x)BT-xCSZ ceramics and the sintering temperature was investigated. The relative density of the (1−x)BT-xCSZ ceramics increased initially and then dropped with increasing sintering temperature, as displayed in Figure 1, suggesting the existence of an optimum sintering temperature (OST) for each composition.
The (1−x)BT-xCSZ ceramics exhibit a number of pores below the OST, above which an over-sintering phenomenon appears. Both of these cases worsen the densification of the ceramics. The relative density of all the samples at the OST is greater than 94%, indicating good sinterability in the samples.
As shown in Figure 1, the OSTs of the (1−x)BT-xCSZ ceramics for x = 0, 0.03, 0.06, 0.09, 0.12, and 0.15 are 1300 °C, 1325 °C, 1360 °C, 1380 °C, 1380 °C, and 1400 °C, respectively. Therefore, a higher sintering temperature is required after doping CSZ in the BT-based ceramics.

3.2. Microstructure

Figure 2 shows the SEM surface micrographs of the (1−x)BT-xCSZ ceramics with x = 0, 0.03, 0.06, 0.09, 0.12, and 0.15 sintered at their respective OST. It can be seen that all the ceramics show a compacted microstructure without any obvious pores. The average grain size of the CSZ-doped BT ceramics was checked by using Nano Measurer software. After calculation by the linear intercept method on SEM images, the average grain size of the samples was determined to be about 26.5 ± 1.5 μm for undoped BT ceramics, and it drops dramatically to 13.2 ± 0.5 μm for 0.85BT-0.15CSZ ceramics with the increasing CSZ content. Therefore, the average grain size is highly relevant with the CSZ concentration. The decreased grain size is due to the introduction of Ca2+, Zr4+, and Sn4+ with larger ionic radii, which have low ionic mobility during sintering, and as a result, inhibit the grain growth [38].

3.3. Crystal Structure

To study the crystal structures and composition-induced phase transition behavior of the (1−x)BT-xCSZ ceramics, the XRD patterns of the sintered samples with different compositions (x = 0.00–0.15) were measured at room temperature, as presented in Figure 3. The characteristic diffraction peaks in Figure 3a reveal the formation of a pure perovskite structure for all the compositions, indicating that the CSZ dopant has diffused completely into the BT lattice to form homogeneous solid solutions without any impurity phases.
Obviously, the ceramics with x = 0–0.03 exhibit a typical tetragonal structure as characterized by the splitting (200)/(002) peaks and a single (111) peak. With the increasing CSZ content, the (111) peak remains almost unchanged (Figure 3b). In comparison, the (200) diffraction peaks gradually broaden in the compositions of x = 0.06–0.09. The (200) and (002) peaks merge into a single peak when the CSZ content increases further to x = 0.12–0.15, indicating the stabilization of a cubic phase in these compositions.
The enlarged XRD patterns of the (200)/(002) peaks of x = 0.06 and 0.09 are given in Figure 3c. Both of their (200)/(002) peaks can be well fitted with three peaks, indicating that these compositions are located in the MPB region. The MPB region can be regarded as a structural bridge between the tetragonal and cubic phases, where these two phases have equal free energy and coexist uniformly.
In order to clarify the detailed structural evolution of the prepared (1−x)BT-xCSZ ceramics, Rietveld refinements for the ceramics with x = 0, 0.15, and 0.06 were carried out using the tetragonal P4mm, cubic Pm 3 ¯ m, and P4mm + Pm 3 ¯ m model, respectively. The refined results are shown in Figure 3d–f. It can be seen that the calculated curves agree well with the observed XRD diffraction profiles, indicating the high reliability of the refined results.
With these observations, we conclude that the crystal structure of the (1−x)BT-xCSZ solid solutions changes from a tetragonal P4mm phase to an MPB region with P4mm and Pm 3 ¯ m phases, and finally turns out to be a cubic Pm 3 ¯ m phase.
Compared with pure BT, it is noted that the (200) peak of the (1−x)BT-xCSZ solid solutions gradually shifts to a lower 2θ degree, indicating the expansion of the unit cells. The expansion of the unit cells arises from the larger ionic radii of Ca2+, Zr4+, and Sn4+ than those of Ba2+ and Ti4+.
The crystal structure and the calculated lattice parameters as a function of x from the refinement results are listed in Table 1. One can notice that the lattice parameters a and b increase, whereas c decreases with increasing CSZ concentration. Therefore, the tetragonality (c/a ratio) of the P4mm phase decreases from 1.01 for pure BT ceramics to 1.003 for the x = 0.06 ceramics and then to 1.00 for the ceramics with higher x values, suggesting the degradation of the P4mm phase.
The effects of the CSZ content on the structural evolution, phase boundary, and lattice parameters calculated from the Rietveld refinements of the BT-based ceramics are shown in Figure 4. As the CSZ concentration increases, a gradual phase transition sequence from tetragonal to MPB, and then to cubic, is clearly revealed.

3.4. Dielectric and Phase Transition Behavior

The permittivity and loss factor of the (1−x)BT-xCSZ (x = 0, 0.03, 0.06, 0.09, 0.12, and 0.15) ceramics at frequencies of 1 kHz to 1 MHz are plotted as a function of temperature, as illustrated in Figure 5. In pure BT ceramic, a sharp dielectric peak independent of frequency is found at Tc = Tm = 125 °C, corresponding to the phase transition temperature from the ferroelectric tetragonal (P4mm) to the paraelectric cubic (Pm 3 ¯ m) phases (Curie temperature Tc) in normal ferroelectric materials. Here Tm refers to the temperature where the permittivity reaches its maximum. The Tc/Tm decreases to 110 °C in x = 0.03.
With the increasing CSZ content (x = 0.06 and x = 0.09), a shoulder gradually develops at the temperature below Tm, and it shifts to a lower temperature as shown in the insert of Figure 5c,d. At the same time, the samples start to show some relaxor behaviors as evidenced by the observation that Tm gradually shifts to higher temperatures with increasing frequency. As a result, a temperature-induced spontaneous transformation from the ferroelectric to ergodic relaxor phases occurs at Tc in x = 0.06 and x = 0.09. A similar phenomenon was also found in PZ-PT-BZN and PMN-BZN-PT systems [39,40,41].
With further increase in the CSZ content, the dielectric curves become evenly diffused, and the value of Tm shows a strong dependence on frequency (Figure 5g–i), suggesting an enhanced relaxor behavior [42,43]. In the compositions of x = 0.12 and 0.15, the dielectric anomaly at Tc disappears, and an ergodic relaxor phase shows up at room temperature.
In relaxor ferroelectrics, the Curie–Weiss law (ε = C/(T − TCW), where ε, C, T, and TCW stands for permittivity, Curie–Weiss constant, measured temperature, and Curie–Weiss temperature, respectively) is found to be satisfied at T > Tb (Burns temperature), where the crystal is of paraelectric (PE) nature. Therefore, by fitting the dielectric curve with the Curie–Weiss law, Tb can be obtained, which determines the phase boundary between the ergodic relaxor state and the paraelectric state.

3.5. Ferroelectric Properties

To further investigate the polarization and phase transition behavior driven by the CSZ dopant, the hysteresis loops of the (1−x)BT-xCSZ ceramics were measured at 10 Hz under various applied fields, as shown in Figure 6a–g. The pure BT ceramic exhibits a saturated P-E hysteresis loop under ±50 kV/cm. With the increase in a small amount of CSZ content, the P-E hysteresis loop becomes well squared (e.g., x = 0.03 and 0.06), indicating a good ferroelectricity at room temperature. With a further increase in the CSZ content, the shapes of the P-E hysteresis loops gradually change from well-squared loops to slim loops, which are characteristic of relaxors.
The values of Pmax, Pr, and Ec versus composition x for the studied ceramics are displayed in Figure 6h,i. Both the maximum polarization (Pmax) and remanent polarization (Pr) measured under 40 kV/cm show an increasing trend first and then decrease with the increasing CSZ content. The increase in Pmax and Pr can be attributed to the phase transformation from a single tetragonal phase to the coexistence of cubic and tetragonal phases, which leads to an easier reorientation of the polarization vectors between different accepted directions and the possible polarization extension due to the flattening of the free energy profile in the MPB region [17,18].
Further increasing the CSZ content leads to the degeneration of the Pr values from 10.2 μC/cm2 (x = 0.06) to 1.3 μC/cm2 (x = 0.15) for the (1−x)BT-xCSZ ceramics, as shown in Figure 6i. The gradual slimming P-E hysteresis loops with smaller Pr are coupled to the enhanced relaxor behavior, as shown in Figure 5g–i.
Moreover, the values of coercive field Ec show a decreasing trend with the increase in CSZ content, which might be related to the increasing presence of the cubic phase and the nanosized domains in the ergodic relaxor state. The nanodomains in the ergodic relaxor state are more responsive to the external electric field than are the macroscopic domains in the ferroelectric state, usually resulting in a slimmer hysteresis loop [44].

3.6. Phase Diagram and Piezoelectric Properties

Based on the analysis of the crystal structure and the dielectric property, a temperature-composition phase diagram of the (1−x)BT-xCSZ ceramics is proposed, as illustrated in Figure 7. The phase diagram studied in this work shows different phase structures and phase transition sequences, consisting of four phase regions, T, T + C (MPB), ER (ergodic relaxor) and cubic phases. With the increasing CSZ content, the tetragonal phase is suppressed with the decreasing tetragonality c/a. It seems that the change of c/a is mainly influenced by the substitution of Sn4+ and Zr4+ for Ti4+ ions, because the replacement of Ca2+ for Ba2+ ion on the A-site has negligible effects on the Tc value [44]. It is noted that the range of the ergodic relaxor phase between Tc and Tb gradually widens, further confirming the enhanced relaxor behavior. The MPB region with the coexistence of C and T phases appears in the composition of 0.06 ≤ x ≤ 0.09.
Figure 7b presents the piezoelectric coefficient of the BT-based ceramics as a function of CSZ content. The value of d33 increases and reaches a maximum value of 388 ± 9 pC/N in the composition of x = 0.06 (in the MPB region), and then decreases with the increasing x. The significantly enhanced piezoelectric coefficient indicates that constructing a phase boundary is an effective way to design lead-free materials with good piezoelectricity.
It should be pointed that noticeable piezoelectricity is observed in the compositions of x > 0.09, which have been determined to be cubic in symmetry by XRD. Therefore, the phase in these compositions is not a real cubic structure at room temperature. Instead, it is a phase with a local polar structure in micro-/nanoscale but with cubic symmetry on average. By applying an electric field (poling), long-range polar order is induced, leading to a detectable macroscopic piezoelectric response [45]. Such a short-range polar structure has been revealed in some relaxor ferroelectrics [46,47]. Further investigations are underway to clarify the relationship between the multiscale structure and electromechanical properties in the (1−x)BT-xCSZ ceramics.

4. Conclusions

In this study, ceramics of the (1−x)BT-xCSZ binary solid solutions have been synthesized by the conventional solid-state reaction method. The effects of CSZ substitution on the crystal structure, dielectric, and piezoelectric properties of the BT ceramics are investigated. With increasing CSZ content, the structure changes from a tetragonal phase to the MPB regions with a mixture of tetragonal and cubic phases, and then toward a cubic phase. The as-prepared (1−x)BT-xCSZ ceramics exhibit dense microstructure. An enhanced relaxor behavior is indicated with the substitution of CSZ. More importantly, a significantly enhanced piezoelectric coefficient of d33 = 388 ± 9 pC/N is attained in the composition of x = 0.06 in the MPB region, where a tetragonal ferroelectric phase and an ergodic relaxor phase with average cubic symmetry coexist. On the basis of the crystal structure and dielectric property analysis, a temperature-composition phase diagram consisting of four phase regions (i.e., tetragonal ferroelectric, MPB ferroelectric, cubic ergodic relaxor, and cubic paraelectric) is established. Our results demonstrate that the newly developed BT-CSZ solid solutions are an attractive lead-free material family for electromechanical transducer applications.

Author Contributions

Preparation and performing of the experiments, electrical properties measurements, manuscript’s writing—origin draft, K.Z.; paper idea, experimental designing, data analysis, manuscript writing—review & editing, P.G., C.L. and Z.L.; experimental investigation and data processing, X.C. and X.H.; data analysis, language polishing, Z.L. and Y.P. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by the National Natural Science Foundation of China (Grant Nos. 52202142 and 51902244), the Natural Science Basic Research Program of Shaanxi Province (Grants Nos. 2022JQ-337 and 2020JQ-710), the Doctoral Scientific Research Startup Foundation of Shaanxi University of Science and Technology (Grants Nos. 2019QNBJ-12 and 2018BJ-07), and the Fundamental Research Funds for the Central Universities of China (Grant No. xzy012021025).

Data Availability Statement

Not applicable.

Acknowledgments

The authors thank Zhixuan Guo for the XRD measurements.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. The relative density of the (1−x)BT-xCSZ ceramics as a function of sintering temperature.
Figure 1. The relative density of the (1−x)BT-xCSZ ceramics as a function of sintering temperature.
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Figure 2. SEM morphologies of the (1−x)BT-xCSZ ceramics with (a) x = 0, (b) x = 0.03, (c) x = 0.06, (d) x = 0.09, (e) x = 0.12, and (f) x = 0.15.
Figure 2. SEM morphologies of the (1−x)BT-xCSZ ceramics with (a) x = 0, (b) x = 0.03, (c) x = 0.06, (d) x = 0.09, (e) x = 0.12, and (f) x = 0.15.
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Figure 3. XRD patterns of (a) the as-sintered (1−x)BT-xCSZ ceramics with different compositions, (b) the amplified patterns at 2θ = 38.4~39.2°, (c) the enlarged XRD patterns of the (200)/(002) peaks and the peak fitting in x = 0.06 and 0.09, (d–f) Rietveld refinement results of the (1−x)BT-xCSZ ceramics with x = 0, x = 0.06 and x = 0.15 at room temperature.
Figure 3. XRD patterns of (a) the as-sintered (1−x)BT-xCSZ ceramics with different compositions, (b) the amplified patterns at 2θ = 38.4~39.2°, (c) the enlarged XRD patterns of the (200)/(002) peaks and the peak fitting in x = 0.06 and 0.09, (d–f) Rietveld refinement results of the (1−x)BT-xCSZ ceramics with x = 0, x = 0.06 and x = 0.15 at room temperature.
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Figure 4. Variations of the crystal structure and lattice parameters as a function of CSZ content for the (1−x)BT-xCSZ ceramics at room temperature.
Figure 4. Variations of the crystal structure and lattice parameters as a function of CSZ content for the (1−x)BT-xCSZ ceramics at room temperature.
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Figure 5. (a–f) Permittivity and loss factor of the (1−x)BT-xCSZ (0 ≤ x ≤ 0.15) ceramics measured at various frequencies. (g–i) Enlarged view of the dielectric peaks for the (1−x)BT-xCSZ ceramics with x = 0.06, 0.09 and 0.12.
Figure 5. (a–f) Permittivity and loss factor of the (1−x)BT-xCSZ (0 ≤ x ≤ 0.15) ceramics measured at various frequencies. (g–i) Enlarged view of the dielectric peaks for the (1−x)BT-xCSZ ceramics with x = 0.06, 0.09 and 0.12.
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Figure 6. Polarization-electric field hysteresis loops measured at room temperature under different electric-field for the (1−x)BT-xCSZ ceramics: (a) x = 0, (b) x = 0.03, (c) x = 0.06, (d) x = 0.09, (e) x = 0.12, and (f) x = 0.15. (g) The P-E loops of the studied ceramics measured at ±40 kV/cm. (h,i) Evolution of the Pmax, Pr, and Ec value as a function of the CSZ content.
Figure 6. Polarization-electric field hysteresis loops measured at room temperature under different electric-field for the (1−x)BT-xCSZ ceramics: (a) x = 0, (b) x = 0.03, (c) x = 0.06, (d) x = 0.09, (e) x = 0.12, and (f) x = 0.15. (g) The P-E loops of the studied ceramics measured at ±40 kV/cm. (h,i) Evolution of the Pmax, Pr, and Ec value as a function of the CSZ content.
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Figure 7. (a) phase diagram and (b) d33 values of the (1−x)BT-xCSZ ceramics as a function of x.
Figure 7. (a) phase diagram and (b) d33 values of the (1−x)BT-xCSZ ceramics as a function of x.
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Table
Table 1. The crystal structure and refined lattice parameters of (1−x)BT-xCSZ ceramics.
Table 1. The crystal structure and refined lattice parameters of (1−x)BT-xCSZ ceramics.
Component 00.060.15
Symmetry TT + CC
Space group P4mmP4mmPm 3 ¯ mPm 3 ¯ m
Lattice parameters parametersa (Å)3.995 (3)4.008 (8)4.011 (2)4.014 (1)
b (Å)3.995 (3)4.008 (8)4.011 (2)4.014 (1)
c (Å)4.035 (2)4.021 (1)4.011 (2)4.014 (1)
c/a1.0101.003 (2)1.0001.000
Cell volumeV (Å3)64.399 (7)64.594 (6)64.529 (4)64.674 (3)
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Zhang, K.; Gao, P.; Liu, C.; Chen, X.; Huang, X.; Pu, Y.; Liu, Z. Structural Evolution and Enhanced Piezoelectric Activity in Novel Lead-Free BaTiO3-Ca(Sn1/2Zr1/2)O3 Solid Solutions. Energies 2022, 15, 7795. https://doi.org/10.3390/en15207795

AMA Style

Zhang K, Gao P, Liu C, Chen X, Huang X, Pu Y, Liu Z. Structural Evolution and Enhanced Piezoelectric Activity in Novel Lead-Free BaTiO3-Ca(Sn1/2Zr1/2)O3 Solid Solutions. Energies. 2022; 15(20):7795. https://doi.org/10.3390/en15207795

Chicago/Turabian Style

Zhang, Ke, Pan Gao, Chang Liu, Xin Chen, Xinye Huang, Yongping Pu, and Zenghui Liu. 2022. "Structural Evolution and Enhanced Piezoelectric Activity in Novel Lead-Free BaTiO3-Ca(Sn1/2Zr1/2)O3 Solid Solutions" Energies 15, no. 20: 7795. https://doi.org/10.3390/en15207795

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