Study of acoustic parameters of lanthanum-gallium tantalate single crystals subjected to cyclic deformation and thermal shock

The effect of crystal anisotropy and defects of the structure formed upon mechanical cyclic deformation and thermal shock on acoustic parameters such as phase velocity, attenuation coefficient, Q-factor of bulk acoustic wave (BAW) has been studied in lanthanum-gallium tantalate (LGT, La₃Ta_0,5Ga_5,5O₁₄) anisotropic piezoelectric single crystals using inner friction (IF) method with multiple piezoelectric vibrator at a frequency of 10⁵ Hz. The anisotropy of the effective elasticity modulus (E), BAW phase velocity (V_p), attenuation coefficient and Q-factor was observed in anisotropic LGT single crystals. It is shown that cyclic deformation of LGT samples under a load of 2.5 kN with the number of load cycles up to 5 x 105 with a cycling frequency of 100 MHz and thermal shock (100 - 120°C) have no effect on the values of the effective elasticity modulus and phase velocity of the longitudinal BAW, respectively: for X-cut — E =111 GPa, V_p = 4250 m/sec; for Z-cut — E = 181 GPa, V_p = 5430 m/sec. The attenuation coefficient of the longitudinal BAW increased by 1.5 - 2 times after cyclic deformation for both X-and Z-cuts, which resulted in a two-fold decrease of the quality factor. Thermal shock has almost no effect on the attenuation coefficient and Q-factor for X-cut samples. For Z-cut samples thermal shock leads to a three-fold increase of the attenuation coefficient and decrease of the Q-factor. Sensitive elements of piezopressure sensors based on langatate should be protected from thermal shock at a temperature above 150°C, and the total number of the mechanical compression cycles of the material should not exceed 5 x 105 cycles at a frequency of 100 - 150 Hz with the loads not exceeding 2.5 kN.

1. Tyapunina N. A., Naimi E. K., Zimenkova G. M. The effect of ultrasound on crystals with defects. — Moscow: Izd. MGU, 1999. — 238 p. [in Russian].

2. Naimi E. K. Anisotropy of the dislocation internal friction in a real crystal: author’s abstract of doctoral thesis. — Moscow, 1993. — 37 p. [in Russian].

3. Naimi E. K., Buzanov O. A., Fedoseev S. A. The Influence of the crystallographic orientation of the specimen on the parameters of bulk acoustic waves in langasite at frequencies 10-5 Hz / Mater. Elektron. Tekh. 2005. N 2. P. 39 - 43 [in Russian].

4. Naimi E. K., Stepanov V A. The Effect of container material on the piezoelectric and acoustic characteristics of langasite crystals / Zavod. Lab. Diagn. Mater. 2014. Vol. 80. N 12. P. 25 - 30 [in Russian].

5. Mill B. V., Pisarevsky Yu. V. Langasite-type materials: from discovery to present state / Proc. 2000 IEEE Inter. Frequency Control Symp. 2000. P 133 - 144.

6. Mill B. V, Butashin A. V, Khojabagyan G. G., et al. Modified rare-earth gallate with the structure of Ca3Ga2Ge4O14 / Dokl. AN SSSR. 1982. Vol. 264. N6. P 1385 -1389 [in Russian].

7. Panich A. A., Marakhovsky M. A., Motin D. V. Crystal and ceramic piezoelectric materials / Inzh. Vestn. Dona. 2011. Vol. 15. N 1. P 53 - 64 [in Russian].

8. RF Pat. 2108418, C1, IEI6 WITH 30 29/34,15/00. A method of growing single crystals of lanthanum-gallium silicate / Buza-nov O. A.; applicant and owner Fomos Ltd — N 97103750/25; appl. 12.03.97; publ. 10.04.1998. Byull. N 10 [in Russian].

9. RF Pat. 2126063, C1, MKI6 WITH 30 29/34,15/00. Method for producing furnace charge for growing single crystals entangling silicate / Koznov G. G.; applicant and owner Rafida Developments Ink (GB). — N 96118840/25; appl. 23.09.96; publ. 10.02.98. Byull. N 4.

10. Araki N. et al. Origin of piezoelectricity for langasite A3Ga5SiO14 (A = La and Nd) under high pressure / Journal of the European Ceramic Society. 2007. N 27. P 4099 - 4102.

11. Blanter M. S., Piguzov Yu. V, Ashmarin G. M., et al. The method of internal friction in metallurgical research. — Moscow: Metallurgiya, 1991. — 248 p. [in Russian].

12. Buzanov O. A., Kozlova N. S., Zabelina E. V, et al. The influence of preparation conditions on optic transmission spectra and electrophysical properties of crystals in the group of lanthanum-gallium silicate / Mater. Elektron. Tekh. 2010. N 1. P 14 - 19 [in Russian].

13. Piezoelectric materials and devices. http://www.newpiezo.com (accessed 13.02.2018) [in Russian].

14. Kugaenko O. M., Petrakov V S., Uvarova S. S., et al. Plastic Deformation of Piezoelectric Lanthanum-Gallium Tantalate Crystals during Cyclic Mechanical Actions / Deform. Razrush. Mater. 2012. N 2. P 16 - 21 [in Russian].

15. Aronova M. A., Berezhkova G. V, Butashin A. V, et al. The strength and ductility of single crystals of La3Ga5SiO14 / Kristallografiya. 1990. P 933 - 938 [in Russian].