- Email: [email protected]
PMN-PT and PIN-PMN-PT single crystals grown by continuous-feeding Bridgman method
Journal of Crystal Growth 531 (2020) 125364
Contents lists available at ScienceDirect
Journal of Crystal Growth journal homepage: www.elsevier.com/locate/jcrysgro
PMN-PT and PIN-PMN-PT single crystals grown by continuous-feeding Bridgman method
T
⁎
Kazuhiko Echizenya , Keiichiro Nakamura, Keisuke Mizuno JFE MINERAL COMPANY, LTD., 1, Niihama-cho, Chuo-ku, Chiba 260-0826, Japan
A R T I C LE I N FO
A B S T R A C T
Communicated by Chung wen Lan
Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) and Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals are superior piezoelectric materials. The single crystal boules grown by the Bridgman method include large property variation due to compositional segregation. We have developed the continuous-feeding Bridgman method to eliminate the compositional segregation. A long size PMN-PT single crystal boule (80 mm in diameter and 320 mm in length) was successfully grown under optimized growth conditions. The boule showed high property uniformity (10% in d33 variation) as a result of high composition uniformity. This results in productivity enhancement of 24% compared to our conventional 220 mm long boules. Two PIN-PMN-PT single crystal boules each with different target composition were also successfully grown. They showed stable properties and also higher coercive field (Ec = 510–550 V/mm) than PMN-PT. One of the crystals exhibited a very high phase transition temperature (Trt = 134 °C). The PIN-PMN-PT single crystals produced during this study will be beneficial for high power or high temperature applications.
Keywords: A1. Segregation A2. Bridgman technique A2. Single crystal growth B1. Perovskites B2. Piezoelectric materials
1. Introduction
characterization of the single crystals was described.
Piezoelectric single crystals such as Pb(Mg1/3Nb2/3)-PbTiO3 (PMNPT) and Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) have attracted attention since they show high electromechanical coupling factors (k33 > 0.8) [1,2]. These single crystals have been utilized for transducers used in medical diagnostic ultrasound systems to obtain better image quality. Single crystal boules are normally grown by the Bridgman method. The unidirectional solidification process causes compositional segregation and the PT contents monotonically increase along the growth direction [3–7]. As a result, the crystal boules have large variations of piezoelectric properties such as piezoelectric constants (d33) and electromechanical coupling factors (k33) along the growth direction. To eliminate the compositional segregation we have developed the continuous-feeding Bridgman method which can control the melt composition during crystal growing and improve the composition uniformity [8–10]. In addition, the continuous-feeding Bridgman method enables long crystal boules to be grown from smaller melt volume compared to the Bridgman method and has excellent composition controllability. In this paper, a long size PMN-PT single crystal boule and PIN-PMNPT single crystal boules with different target compositions were grown taking advantage of the continuous-feeding Bridgman method. The
2. Experimental
⁎
2.1. Crystal growth A schematic of the growth system of the continuous-feeding Bridgman method is shown in Fig. 1. A feeding mechanism which supplies PMN-PT or PIN-PMN-PT ceramics at a precise feeding rate was installed on the top of a vertical Bridgman furnace. The furnace consists of heaters, a support tube and a levitation mechanism for a main crucible. The ceramics were synthesized from Pb3O4, MgO, Nb2O5 TiO2 and In2O3 powder by columbite precursor procedure. A 〈0 1 1〉 seed crystal was placed at the bottom of the platinum main crucible and initial PMN-PT or PIN-PMN-PT ceramics were loaded in the main crucible. For PIN-PMN-PT single crystal growth, main crucibles of 250 mm in length were used. For PMN-PT single crystal growth, a main crucible of 350 mm in length was used to expand the single crystal boule length. The ceramics were melted by heating up to more than the melting point (~1300 °C). Then the continuous-feeding growth started after soaking for 16hr. The continuous-feeding Bridgman method is schematically shown in Fig. 2. The crucible was lowered toward the low temperature zone of
Corresponding author. E-mail address: [email protected] (K. Echizenya).
https://doi.org/10.1016/j.jcrysgro.2019.125364 Received 9 August 2019; Received in revised form 14 November 2019; Accepted 18 November 2019 Available online 19 November 2019 0022-0248/ © 2019 Elsevier B.V. All rights reserved.
Journal of Crystal Growth 531 (2020) 125364
K. Echizenya, et al.
the furnace at an appropriate speed (less than 1.0 mm/hr) and at the same time additional PMN-PT or PIN-PMN-PT ceramics were continuously dropped from the feeding mechanism. After the ceramics were melted in a upper crucible, the droplets were supplied to the melt in the main crucible. The composition of the synthesized ceramics, the lowering speed of the main crucible, the feeding rate and the temperature distribution in the furnace were optimized in order to suppress the variation of the melt composition during the crystal growth. After completion of the continuous-feeding growth, the crystal boule was cooled down to room temperature in the furnace. One PMN-PT and two PIN-PMN-PT single crystal boules were grown. The target compositions were 0.70PMN-0.30PT, 0.24PIN-0.46PMN-0.30PT and 0.31PIN0.43PMN-0.26PT. 2.2. Characterization {0 0 1} oriented plates were cut from the grown crystal boules evenly along the growth direction for evaluation. X-ray fluorescence spectrometer (Rigaku ZSX Primus IV) was used to analyze the composition of the plates. Gold and nichrome layers were deposited on the plate surfaces by sputtering as electrodes. The PMN-PT and PIN-PMNPT plates were poled under DC electric fields of 500 V/mm and 1000 V/ mm, respectively. Dielectric properties were measured at 1 kHz in frequency with an impedance analyzer (HP4192A). Piezoelectric coefficients (d33) were measured with a piezo d33 meter (ZJ-3D). Polarization hysteresis curves were measured at 10 Hz in frequency using a ferroelectric characteristics evaluation system (Toyo Corporation FCE-3). The temperature dependence of permittivity was measured at 1 kHz in frequency from room temperature to 190 °C with an impedance analyzer (HP4192A). Electromechanical coupling factors (k33) were determined using an impedance gain phase analyzer (HP4294A).
Fig. 1. Schematic diagram of growth system for continuous-feeding Bridgman method: a – feeding mechanism; b – main crucible; c – heater; d – seed; e – support tube; f – levitation mechanism.
3. Results and discussion 3.1. PMN-PT crystal A PMN-PT single crystal boule of 80 mm in diameter and 320 mm in length was successfully grown. The as-grown boule is shown in Fig. 3. In our previous results, the crystal length was 220 mm [10]. Expanding of the crystal length by 45% is accomplished. The boule was grown from a small volume melt (less than 80 mm in depth). In case of conventional Bridgman method, the melt depth of 320 mm is required to grow a 320 mm long boule. The crucible damage which sometimes causes melt leaks should therefore be reduced. This will contribute to the successful growth. A {0 0 1} oriented wafer sliced from the boule is shown in Fig. 4. There are no macro defects such as cracks and polycrystalline region. Some cracks were observed only on wafers sliced from the region of
Fig. 2. Schematic concept of continuous-feeding Bridgman method: a – upper crucible; b – melt; c – seed; d – ceramics dropped from feeding mechanism; e – crystal; f – main crucible.
Fig. 3. As grown PMN-PT single crystal boule grown by continuous-feeding Bridgman method. 2
Journal of Crystal Growth 531 (2020) 125364
K. Echizenya, et al.
Fig. 6. Piezoelectric coefficient of 320 mm and 220 mm long PMN-PT single crystal boules along growth direction.
Fig. 4. Wafer sliced from PMN-PT single crystal boule grown by continuousfeeding Bridgman method.
60 mm in length from the boule end. The cracks are not caused by expanding of the boule length, as the same cracks in the boule end portion are observed even in a 220 mm long boule [10]. TiO2 content distributions of the 320 mm long boule and a 220 mm long boule (our conventional size) along the growth direction are shown in Fig. 5. Both TiO2 contents range from 5.95 to 6.15 wt% (4% in variation) in most part of the boules. It should be noted that the content of the 320 mm long boule is well controlled in a tight range even in the expanding region (200–300 mm in position). The 320 mm long boule maintains the same composition uniformity as the 220 mm long boule. Piezoelectric coefficient (d33) distributions of the 320 mm long and 220 mm long PMN-PT single crystal boules are shown in Fig. 6. Both boules show almost the same d33 (~1700 pC/N) over their whole straight body region. The d33 ranges from 1590 to 1760 pC/N (10% in variation) for the 320 mm long boule and from 1650 to 1880 pC/N (13% in variation) for the 220 mm long boule, respectively. It is found that the 320 mm long crystal boule has almost the same property uniformity as the 220 mm long crystal boule. The above demonstrates that the continuous-feeding Bridgman method enables the expansion of the PMN-PT single crystal boule up to 320 mm in length without any deterioration of crystal quality. This expansion delivers a productivity increase of 24%. 3.2. PIN-PMN-PT crystal In2O3 and TiO2 content distributions of PIN-PMN-PT single crystal boules along the growth direction are shown in Fig. 7. All contents are
Fig. 7. Distributions of (a) In2O3 content and (b) TiO2 content along growth direction.
controlled in a tight range in their whole straight body. The variation is 3% which is almost the same as the PMN-PT single crystal boule shown in Fig. 5. High composition uniformity is maintained also in ternary PIN-PMN-PT single crystals. 0.24PIN-0.46PMN-0.30PT crystal shows lower In2O3 (PIN) content and higher TiO2 (PT) content. On the other hand, 0.31PIN-0.43PMN-0.26PT crystal shows higher In2O3 (PIN) content and lower TiO2 (PT) content. The results reflect the target
Fig. 5. TiO2 content distributions of 320 mm and 220 mm long PMN-PT single crystal boules along growth direction. 3
Journal of Crystal Growth 531 (2020) 125364
K. Echizenya, et al.
Fig. 8. d33 distributions of PIN-PMN-PT single crystal boules along growth direction.
Fig. 10. Temperature dependence of dielectric constant for PIN-PMN-PT single crystals.
compositions and demonstrate that the continuous-feeding Bridgman method has excellent composition controllability. The d33 distributions of the PIN-PMN-PT single crystal boules along the growth direction are shown in Fig. 8. Both d33 are almost constant over the whole straight body. The variation of the 0.24PIN-0.46PMN0.30PT and the 0.31PIN-0.43PMN-0.26PT single crystal boule are 110 pC/N and 140 pC/N, respectively. Those values are slightly smaller than the PMN-PT single crystal boule shown in Fig. 6. The d33 of 0.24PIN-0.46PMN-0.30PT single crystal is 1.6 times higher than 0.31PIN-0.43PMN-0.26PT single crystal, as 0.24PIN-0.46PMN-0.30PT is near the morphotropic phase boundary composition. Ferroelectric hysteresis curves of PMN-PT and PIN-PMN-PT single crystals are shown in Fig. 9. All crystals show almost the same remanent polarization (~25 uC/cm2). The coercive fields (Ec) of both PIN-PMNPT crystals are around 500 V/mm which is two times larger than the PMN-PT crystal. The higher PIN content crystal (0.31PIN-0.43PMN0.26PT) has slightly larger Ec. These results show that the PIN component is effective for increasing the coercive field. Temperature dependence of the dielectric constant for the PINPMN-PT single crystals is shown in Fig. 10. The temperatures of some dielectric constant peaks are obviously different. The tetragonal to cubic phase transition temperature (Tc) of the 0.31PIN-0.43PMN0.26PT crystal is lower than that of the 0.24PIN-0.46PMN-0.30PT crystal. On the otherhand, the rhombohedral to tetragonal phase transition temperature (Trt) of the 0.31PIN-0.43PMN-0.26PT crystal is
134 °C which is higher than the 0.24PIN-0.46PMN-0.30PT crystal by 32 °C. Higher PIN and lower PT composition is effective to increase Trt. 3.3. Property comparison Typical properties of 0.70PMN-0.30PT, 0.24PIN-0.46PMN-0.30PT and 0.31PIN-0.43PMN-0.26PT single crystals are summarized in Table 1. The 0.70PMN-0.30PT crystal has the highest dielectric constant and k33. The 0.24PIN-0.46PMN-0.30PT crystal has almost the same piezoelectric properties as the 0.70PMN-0.30PT crystal and higher Ec than the 0.70PMN-0.30PT crystal. Therefore, 0.24PIN0.46PMN-0.30PT crystals will be beneficial for high power piezoelectric applications. The 0.31PIN-0.43PMN-0.26PT crystal has slightly low dielectric and piezoelectric properties but the highest Trt. Therefore 0.31PIN-0.43PMN-0.26PT crystals will be useful for high temperature applications. 4. Conclusion A PMN-PT single crystal boule of 80 mm in diameter and 320 mm in length was successfully grown by the continuous-feeding Bridgman method. The composition was controlled in a tight range (4% in TiO2 content variation) and high property uniformity (10% in d33 variation) was accomplished. The productivity increased by 24% compared to our conventional 220 mm long boules. Two PIN-PMN-PT single crystal boules with different stable properties were successfully grown utilizing the composition controllability of the continuous-feeding Bridgman method. Both crystal showed higher Ec (~500 V/mm) than the PMN-PT crystal. Therefore, PIN-PMNPT crystals will be better for high power applications. The high PIN and low PT composition (0.31PIN-0.43PMN-0.26PT) crystal showed highest Trt (134 °C). Therefore, 0.31PIN-0.43PMN-0.26PT crystals will be Table 1 Typical dielectric and piezoelectric properties for 0.70PMN-0.30PT, 0.24PIN0.46PMN-0.30PT and 0.31PIN-0.43PMN-0.26PT single crystals. PIN PMN PT ε33/ε0 tan δ (%) k33 d33 (pC/N) Ec (V/mm) Trt (℃) Tc (℃)
Fig. 9. Ferroelectric hysteresis of PMN-PT and PIN-PMN-PT single crystals. 4
0 0.70 0.30 6000 0.5 0.94 1780 220 92 143
0.24 0.46 0.30 5100 0.5 0.94 1830 510 102 179
0.32 0.41 0.27 3500 0.5 0.90 1090 560 138 151
Journal of Crystal Growth 531 (2020) 125364
K. Echizenya, et al.
effective for applications in high temperature.
[3] M.C. Shin, S.J. Chung, S.-G. Lee, R.S. Feigelson, Growth and observation of domain structure of Lead Magnesium Niobate-Lead Titanate Single Crystals, J. Cryst. Growth 263 (2004) 412–420, https://doi.org/10.1016/j.jcrysgro.2003.12.024. [4] P. Han, J. Tian, W. Yan, Bridgman growth and properties of PMN-PT-based single crystals, in: Z.G. Ye (Ed.), Handbook of Advanced Dielectric, Piezoelectric and Ferroelectric Materials, NY, CRC Press, New York, 2008, pp. 3–37. [5] W.S. Hackenberger, J. Luo, X. Jiang, K.A. Snook, P.W. Pehrig, S. Zhang, T.R. Shrout, Recent developments and applications of piezoelectric crystals, in: Z.G. Ye (Ed.), Handbook of Advanced Dielectric, Piezoelectric and Ferroelectric Materials, NY, CRC Press, New York, 2008, pp. 73–100. [6] H. Luo, G. Xu, H. Xu, P. Wang, Z. Yin, Compositional homogeneity and electrical properties of lead magnesium niobate titanate single crystals grown by a modified bridgman technique, Jpn. J. Appl. Phys. 39 (2000) 5581–5585, https://doi.org/10. 1143/JJAP.39.5581. [7] F. Li, S. Zhang, Z. Xu, X. Wei, J. Luo, T.R. Shrout, Electromechanical properties of tetragonal Pb(In1/2Nb1/2)O3−Pb(Mg1/3Nb2/3)O3−PbTiO3 ferroelectric crystals, J. Appl. Phys. 107 (2010) 054107, https://doi.org/10.1063/1.3331407. [8] K. Echizenya, M. Matsushita, Continuous feed growth and characterization of PMNPT single crystals, Proc. 2011 IEEE Ultrason. Symp. 2011, pp. 1813–1816, , https:// doi.org/10.1109/ULTSYM.2011.0453. [9] M. Matsushita, K. Echizenya, Continuous feeding growth of ternary PIN-PMN-PT single crystals, Proc. 2014 IEEE Ultrason. Symp. 2014, pp. 1–4, , https://doi.org/10. 1109/ISAF.2014.6922994. [10] K. Echizenya, K. Nakamura, Piezoelectric single crystals grown by continuous feeding growth method, 17th US-Japan Seminar on Dielectric and Piezoelectric Ceramics Extended Abstracts, 2015, pp. 227–230.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments This work was partially supported by the U.S. Office of Naval Research Global, United States [grant numbers N62909-19-1-2048, N62909-14-1-N218]. References [1] S.E. Park, T.R. Shrout, Ultrahigh strain and piezoelectric behavior in relaxor based ferroelectric single crystals, J. Appl. Phys. 82 (1997) 1804, https://doi.org/10. 1063/1.365983. [2] Y. Hosono, Y. Yamashita, H. Sakamoto, N. Ichinose, Growth of single crystals of high-curie-temperature Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ternary systems near morphotropic phase boundary, Jpn. J. Appl. Phys. 42 (2003) 5681, https://doi.org/10.1143/JJAP.42.5681.
5
Contents lists available at ScienceDirect
Journal of Crystal Growth journal homepage: www.elsevier.com/locate/jcrysgro
PMN-PT and PIN-PMN-PT single crystals grown by continuous-feeding Bridgman method
T
⁎
Kazuhiko Echizenya , Keiichiro Nakamura, Keisuke Mizuno JFE MINERAL COMPANY, LTD., 1, Niihama-cho, Chuo-ku, Chiba 260-0826, Japan
A R T I C LE I N FO
A B S T R A C T
Communicated by Chung wen Lan
Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) and Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) single crystals are superior piezoelectric materials. The single crystal boules grown by the Bridgman method include large property variation due to compositional segregation. We have developed the continuous-feeding Bridgman method to eliminate the compositional segregation. A long size PMN-PT single crystal boule (80 mm in diameter and 320 mm in length) was successfully grown under optimized growth conditions. The boule showed high property uniformity (10% in d33 variation) as a result of high composition uniformity. This results in productivity enhancement of 24% compared to our conventional 220 mm long boules. Two PIN-PMN-PT single crystal boules each with different target composition were also successfully grown. They showed stable properties and also higher coercive field (Ec = 510–550 V/mm) than PMN-PT. One of the crystals exhibited a very high phase transition temperature (Trt = 134 °C). The PIN-PMN-PT single crystals produced during this study will be beneficial for high power or high temperature applications.
Keywords: A1. Segregation A2. Bridgman technique A2. Single crystal growth B1. Perovskites B2. Piezoelectric materials
1. Introduction
characterization of the single crystals was described.
Piezoelectric single crystals such as Pb(Mg1/3Nb2/3)-PbTiO3 (PMNPT) and Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) have attracted attention since they show high electromechanical coupling factors (k33 > 0.8) [1,2]. These single crystals have been utilized for transducers used in medical diagnostic ultrasound systems to obtain better image quality. Single crystal boules are normally grown by the Bridgman method. The unidirectional solidification process causes compositional segregation and the PT contents monotonically increase along the growth direction [3–7]. As a result, the crystal boules have large variations of piezoelectric properties such as piezoelectric constants (d33) and electromechanical coupling factors (k33) along the growth direction. To eliminate the compositional segregation we have developed the continuous-feeding Bridgman method which can control the melt composition during crystal growing and improve the composition uniformity [8–10]. In addition, the continuous-feeding Bridgman method enables long crystal boules to be grown from smaller melt volume compared to the Bridgman method and has excellent composition controllability. In this paper, a long size PMN-PT single crystal boule and PIN-PMNPT single crystal boules with different target compositions were grown taking advantage of the continuous-feeding Bridgman method. The
2. Experimental
⁎
2.1. Crystal growth A schematic of the growth system of the continuous-feeding Bridgman method is shown in Fig. 1. A feeding mechanism which supplies PMN-PT or PIN-PMN-PT ceramics at a precise feeding rate was installed on the top of a vertical Bridgman furnace. The furnace consists of heaters, a support tube and a levitation mechanism for a main crucible. The ceramics were synthesized from Pb3O4, MgO, Nb2O5 TiO2 and In2O3 powder by columbite precursor procedure. A 〈0 1 1〉 seed crystal was placed at the bottom of the platinum main crucible and initial PMN-PT or PIN-PMN-PT ceramics were loaded in the main crucible. For PIN-PMN-PT single crystal growth, main crucibles of 250 mm in length were used. For PMN-PT single crystal growth, a main crucible of 350 mm in length was used to expand the single crystal boule length. The ceramics were melted by heating up to more than the melting point (~1300 °C). Then the continuous-feeding growth started after soaking for 16hr. The continuous-feeding Bridgman method is schematically shown in Fig. 2. The crucible was lowered toward the low temperature zone of
Corresponding author. E-mail address: [email protected] (K. Echizenya).
https://doi.org/10.1016/j.jcrysgro.2019.125364 Received 9 August 2019; Received in revised form 14 November 2019; Accepted 18 November 2019 Available online 19 November 2019 0022-0248/ © 2019 Elsevier B.V. All rights reserved.
Journal of Crystal Growth 531 (2020) 125364
K. Echizenya, et al.
the furnace at an appropriate speed (less than 1.0 mm/hr) and at the same time additional PMN-PT or PIN-PMN-PT ceramics were continuously dropped from the feeding mechanism. After the ceramics were melted in a upper crucible, the droplets were supplied to the melt in the main crucible. The composition of the synthesized ceramics, the lowering speed of the main crucible, the feeding rate and the temperature distribution in the furnace were optimized in order to suppress the variation of the melt composition during the crystal growth. After completion of the continuous-feeding growth, the crystal boule was cooled down to room temperature in the furnace. One PMN-PT and two PIN-PMN-PT single crystal boules were grown. The target compositions were 0.70PMN-0.30PT, 0.24PIN-0.46PMN-0.30PT and 0.31PIN0.43PMN-0.26PT. 2.2. Characterization {0 0 1} oriented plates were cut from the grown crystal boules evenly along the growth direction for evaluation. X-ray fluorescence spectrometer (Rigaku ZSX Primus IV) was used to analyze the composition of the plates. Gold and nichrome layers were deposited on the plate surfaces by sputtering as electrodes. The PMN-PT and PIN-PMNPT plates were poled under DC electric fields of 500 V/mm and 1000 V/ mm, respectively. Dielectric properties were measured at 1 kHz in frequency with an impedance analyzer (HP4192A). Piezoelectric coefficients (d33) were measured with a piezo d33 meter (ZJ-3D). Polarization hysteresis curves were measured at 10 Hz in frequency using a ferroelectric characteristics evaluation system (Toyo Corporation FCE-3). The temperature dependence of permittivity was measured at 1 kHz in frequency from room temperature to 190 °C with an impedance analyzer (HP4192A). Electromechanical coupling factors (k33) were determined using an impedance gain phase analyzer (HP4294A).
Fig. 1. Schematic diagram of growth system for continuous-feeding Bridgman method: a – feeding mechanism; b – main crucible; c – heater; d – seed; e – support tube; f – levitation mechanism.
3. Results and discussion 3.1. PMN-PT crystal A PMN-PT single crystal boule of 80 mm in diameter and 320 mm in length was successfully grown. The as-grown boule is shown in Fig. 3. In our previous results, the crystal length was 220 mm [10]. Expanding of the crystal length by 45% is accomplished. The boule was grown from a small volume melt (less than 80 mm in depth). In case of conventional Bridgman method, the melt depth of 320 mm is required to grow a 320 mm long boule. The crucible damage which sometimes causes melt leaks should therefore be reduced. This will contribute to the successful growth. A {0 0 1} oriented wafer sliced from the boule is shown in Fig. 4. There are no macro defects such as cracks and polycrystalline region. Some cracks were observed only on wafers sliced from the region of
Fig. 2. Schematic concept of continuous-feeding Bridgman method: a – upper crucible; b – melt; c – seed; d – ceramics dropped from feeding mechanism; e – crystal; f – main crucible.
Fig. 3. As grown PMN-PT single crystal boule grown by continuous-feeding Bridgman method. 2
Journal of Crystal Growth 531 (2020) 125364
K. Echizenya, et al.
Fig. 6. Piezoelectric coefficient of 320 mm and 220 mm long PMN-PT single crystal boules along growth direction.
Fig. 4. Wafer sliced from PMN-PT single crystal boule grown by continuousfeeding Bridgman method.
60 mm in length from the boule end. The cracks are not caused by expanding of the boule length, as the same cracks in the boule end portion are observed even in a 220 mm long boule [10]. TiO2 content distributions of the 320 mm long boule and a 220 mm long boule (our conventional size) along the growth direction are shown in Fig. 5. Both TiO2 contents range from 5.95 to 6.15 wt% (4% in variation) in most part of the boules. It should be noted that the content of the 320 mm long boule is well controlled in a tight range even in the expanding region (200–300 mm in position). The 320 mm long boule maintains the same composition uniformity as the 220 mm long boule. Piezoelectric coefficient (d33) distributions of the 320 mm long and 220 mm long PMN-PT single crystal boules are shown in Fig. 6. Both boules show almost the same d33 (~1700 pC/N) over their whole straight body region. The d33 ranges from 1590 to 1760 pC/N (10% in variation) for the 320 mm long boule and from 1650 to 1880 pC/N (13% in variation) for the 220 mm long boule, respectively. It is found that the 320 mm long crystal boule has almost the same property uniformity as the 220 mm long crystal boule. The above demonstrates that the continuous-feeding Bridgman method enables the expansion of the PMN-PT single crystal boule up to 320 mm in length without any deterioration of crystal quality. This expansion delivers a productivity increase of 24%. 3.2. PIN-PMN-PT crystal In2O3 and TiO2 content distributions of PIN-PMN-PT single crystal boules along the growth direction are shown in Fig. 7. All contents are
Fig. 7. Distributions of (a) In2O3 content and (b) TiO2 content along growth direction.
controlled in a tight range in their whole straight body. The variation is 3% which is almost the same as the PMN-PT single crystal boule shown in Fig. 5. High composition uniformity is maintained also in ternary PIN-PMN-PT single crystals. 0.24PIN-0.46PMN-0.30PT crystal shows lower In2O3 (PIN) content and higher TiO2 (PT) content. On the other hand, 0.31PIN-0.43PMN-0.26PT crystal shows higher In2O3 (PIN) content and lower TiO2 (PT) content. The results reflect the target
Fig. 5. TiO2 content distributions of 320 mm and 220 mm long PMN-PT single crystal boules along growth direction. 3
Journal of Crystal Growth 531 (2020) 125364
K. Echizenya, et al.
Fig. 8. d33 distributions of PIN-PMN-PT single crystal boules along growth direction.
Fig. 10. Temperature dependence of dielectric constant for PIN-PMN-PT single crystals.
compositions and demonstrate that the continuous-feeding Bridgman method has excellent composition controllability. The d33 distributions of the PIN-PMN-PT single crystal boules along the growth direction are shown in Fig. 8. Both d33 are almost constant over the whole straight body. The variation of the 0.24PIN-0.46PMN0.30PT and the 0.31PIN-0.43PMN-0.26PT single crystal boule are 110 pC/N and 140 pC/N, respectively. Those values are slightly smaller than the PMN-PT single crystal boule shown in Fig. 6. The d33 of 0.24PIN-0.46PMN-0.30PT single crystal is 1.6 times higher than 0.31PIN-0.43PMN-0.26PT single crystal, as 0.24PIN-0.46PMN-0.30PT is near the morphotropic phase boundary composition. Ferroelectric hysteresis curves of PMN-PT and PIN-PMN-PT single crystals are shown in Fig. 9. All crystals show almost the same remanent polarization (~25 uC/cm2). The coercive fields (Ec) of both PIN-PMNPT crystals are around 500 V/mm which is two times larger than the PMN-PT crystal. The higher PIN content crystal (0.31PIN-0.43PMN0.26PT) has slightly larger Ec. These results show that the PIN component is effective for increasing the coercive field. Temperature dependence of the dielectric constant for the PINPMN-PT single crystals is shown in Fig. 10. The temperatures of some dielectric constant peaks are obviously different. The tetragonal to cubic phase transition temperature (Tc) of the 0.31PIN-0.43PMN0.26PT crystal is lower than that of the 0.24PIN-0.46PMN-0.30PT crystal. On the otherhand, the rhombohedral to tetragonal phase transition temperature (Trt) of the 0.31PIN-0.43PMN-0.26PT crystal is
134 °C which is higher than the 0.24PIN-0.46PMN-0.30PT crystal by 32 °C. Higher PIN and lower PT composition is effective to increase Trt. 3.3. Property comparison Typical properties of 0.70PMN-0.30PT, 0.24PIN-0.46PMN-0.30PT and 0.31PIN-0.43PMN-0.26PT single crystals are summarized in Table 1. The 0.70PMN-0.30PT crystal has the highest dielectric constant and k33. The 0.24PIN-0.46PMN-0.30PT crystal has almost the same piezoelectric properties as the 0.70PMN-0.30PT crystal and higher Ec than the 0.70PMN-0.30PT crystal. Therefore, 0.24PIN0.46PMN-0.30PT crystals will be beneficial for high power piezoelectric applications. The 0.31PIN-0.43PMN-0.26PT crystal has slightly low dielectric and piezoelectric properties but the highest Trt. Therefore 0.31PIN-0.43PMN-0.26PT crystals will be useful for high temperature applications. 4. Conclusion A PMN-PT single crystal boule of 80 mm in diameter and 320 mm in length was successfully grown by the continuous-feeding Bridgman method. The composition was controlled in a tight range (4% in TiO2 content variation) and high property uniformity (10% in d33 variation) was accomplished. The productivity increased by 24% compared to our conventional 220 mm long boules. Two PIN-PMN-PT single crystal boules with different stable properties were successfully grown utilizing the composition controllability of the continuous-feeding Bridgman method. Both crystal showed higher Ec (~500 V/mm) than the PMN-PT crystal. Therefore, PIN-PMNPT crystals will be better for high power applications. The high PIN and low PT composition (0.31PIN-0.43PMN-0.26PT) crystal showed highest Trt (134 °C). Therefore, 0.31PIN-0.43PMN-0.26PT crystals will be Table 1 Typical dielectric and piezoelectric properties for 0.70PMN-0.30PT, 0.24PIN0.46PMN-0.30PT and 0.31PIN-0.43PMN-0.26PT single crystals. PIN PMN PT ε33/ε0 tan δ (%) k33 d33 (pC/N) Ec (V/mm) Trt (℃) Tc (℃)
Fig. 9. Ferroelectric hysteresis of PMN-PT and PIN-PMN-PT single crystals. 4
0 0.70 0.30 6000 0.5 0.94 1780 220 92 143
0.24 0.46 0.30 5100 0.5 0.94 1830 510 102 179
0.32 0.41 0.27 3500 0.5 0.90 1090 560 138 151
Journal of Crystal Growth 531 (2020) 125364
K. Echizenya, et al.
effective for applications in high temperature.
[3] M.C. Shin, S.J. Chung, S.-G. Lee, R.S. Feigelson, Growth and observation of domain structure of Lead Magnesium Niobate-Lead Titanate Single Crystals, J. Cryst. Growth 263 (2004) 412–420, https://doi.org/10.1016/j.jcrysgro.2003.12.024. [4] P. Han, J. Tian, W. Yan, Bridgman growth and properties of PMN-PT-based single crystals, in: Z.G. Ye (Ed.), Handbook of Advanced Dielectric, Piezoelectric and Ferroelectric Materials, NY, CRC Press, New York, 2008, pp. 3–37. [5] W.S. Hackenberger, J. Luo, X. Jiang, K.A. Snook, P.W. Pehrig, S. Zhang, T.R. Shrout, Recent developments and applications of piezoelectric crystals, in: Z.G. Ye (Ed.), Handbook of Advanced Dielectric, Piezoelectric and Ferroelectric Materials, NY, CRC Press, New York, 2008, pp. 73–100. [6] H. Luo, G. Xu, H. Xu, P. Wang, Z. Yin, Compositional homogeneity and electrical properties of lead magnesium niobate titanate single crystals grown by a modified bridgman technique, Jpn. J. Appl. Phys. 39 (2000) 5581–5585, https://doi.org/10. 1143/JJAP.39.5581. [7] F. Li, S. Zhang, Z. Xu, X. Wei, J. Luo, T.R. Shrout, Electromechanical properties of tetragonal Pb(In1/2Nb1/2)O3−Pb(Mg1/3Nb2/3)O3−PbTiO3 ferroelectric crystals, J. Appl. Phys. 107 (2010) 054107, https://doi.org/10.1063/1.3331407. [8] K. Echizenya, M. Matsushita, Continuous feed growth and characterization of PMNPT single crystals, Proc. 2011 IEEE Ultrason. Symp. 2011, pp. 1813–1816, , https:// doi.org/10.1109/ULTSYM.2011.0453. [9] M. Matsushita, K. Echizenya, Continuous feeding growth of ternary PIN-PMN-PT single crystals, Proc. 2014 IEEE Ultrason. Symp. 2014, pp. 1–4, , https://doi.org/10. 1109/ISAF.2014.6922994. [10] K. Echizenya, K. Nakamura, Piezoelectric single crystals grown by continuous feeding growth method, 17th US-Japan Seminar on Dielectric and Piezoelectric Ceramics Extended Abstracts, 2015, pp. 227–230.
Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments This work was partially supported by the U.S. Office of Naval Research Global, United States [grant numbers N62909-19-1-2048, N62909-14-1-N218]. References [1] S.E. Park, T.R. Shrout, Ultrahigh strain and piezoelectric behavior in relaxor based ferroelectric single crystals, J. Appl. Phys. 82 (1997) 1804, https://doi.org/10. 1063/1.365983. [2] Y. Hosono, Y. Yamashita, H. Sakamoto, N. Ichinose, Growth of single crystals of high-curie-temperature Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 ternary systems near morphotropic phase boundary, Jpn. J. Appl. Phys. 42 (2003) 5681, https://doi.org/10.1143/JJAP.42.5681.
5