Electro-elastic features of Ca3Ta(Ga0.7Al0.3)3Si2O14 single crystals grown in different atmospheres

Abstract

Langasite-type crystals have emerged as promising candidates for high-temperature piezoelectric sensing. In this study, high-quality Ca₃Ta(Ga_0.7Al_0.3)₃Si₂O₁₄ (CTGAS) crystals were grown via the Czochralski (Cz) pulling method under two distinct atmospheres: pure N₂ and O₂-mixed (99 vol% N₂ + 1 vol% O₂). Their electrical resistivity and electro-elastic properties were systematically investigated within 25–800 °C. It was found that CTGAS crystals grown in pure N₂ exhibited an electrical resistivity of ∼4.0 × 10⁶ Ω cm at 800 °C, which was fourfold higher than those grown in an O₂-mixed atmosphere. The longitudinal piezoelectric coefficient d₁₁ was measured to be 4.2 pC N⁻¹ (N₂) and 4.6 pC N⁻¹ (O₂-mixed) at room temperature, with <10% variation over 25–800 °C. The shear piezoelectric coefficient d₁₄ decreased from 8.3 pC N⁻¹ (N₂) and 9.2 pC N⁻¹ (O₂-mixed) at room temperature to 4.4 pC N⁻¹ and 4.7 pC N⁻¹ at 800 °C, respectively. Based on the above results, the optimized crystal cuts for lateral and thickness shear modes were designed, exhibiting a low variation of <5% across the tested temperature range of 25–800 °C. These results highlight the potential of CTGAS for stable high-temperature piezoelectric sensors (e.g., force and acceleration sensors).