Transport and Electromechanical Properties of Ca3TaGa3Si2O14 Piezoelectric Crystals at Extreme Temperatures

Abstract

Transport mechanisms in structurally ordered piezoelectric Ca3TaGa3Si2O14 (CTGS) single crystals are studied in the temperature range of 1000-1300 °C by application of the isotope 18O as a tracer and subsequent analysis of diffusion profiles of this isotope using secondary ion mass spectrometry (SIMS). Determined oxygen self-diffusion coefficients enable calculation of oxygen ion contribution to the total conductivity, which is shown to be small. Since very low contributions of the cations have to be expected, the total conductivity must be dominated by electron transport. Ion and electron conductivities are governed by different mechanisms with activation energies (1.9±0.1) eV and (1.2±0.07) eV, respectively. Further, the electromechanical losses are studied as a function of temperature by means of impedance spectroscopy on samples with electrodes and a contactless tone-burst excitation technique. At temperatures above 650 °C the conductivity-related losses are dominant. Finally, the operation of CTGS resonators is demonstrated at cryogenic temperatures and materials piezoelectric strain constants are determined from 4.2 K to room temperature.

High-temperature behavior of housed piezoelectric resonators based on CTGS

“…Here, Rh impurities may have lead to a compensation of unintended defects. Furthermore, the inverse Q factor shows a maximum at about 400 • C; it can be attributed to anelastic relaxations of point defects (Suhak et al, 2018;Suhak et. al., 2019).…”

“…Since the impedance of sapphire is still in the 10 6 range at 1000 • C, i.e., it exceeds the bulk impedance of the resonator by several orders of magnitude, its influence on the resonant properties of CTGS is negligible. The high temperature loss in CTGS is described by Suhak et al (2018) andSuhak et. al.…”

“…al., 2019). Above 650 • C, the losses are governed by piezoelectric/conductivity relaxation (Suhak et. al., 2019).…”

“…Catangasite (Ca 3 TaGa 3 Si 2 O 14 -CTGS) gained considerable attention since it exhibits an ordered crystal structure and, thus, shows significantly lower electromechanical losses (Johnson et. al., 2014;Suhak et. al., 2019).…”

“…where e 26 , c 66 and ε 11 are the piezoelectric coefficient, stiffness coefficient and dielectric permittivity, respectively, equals 11 % at room temperature and constantly increases up to about 15 % at 1000 • C (Zhang et. al., 2009;Zhang and Yu, 2011;Suhak et al, 2018;Suhak et. al., 2019).…”