Growth and high temperature properties of Ca₃Ta(Al_0.9Ga_0.1)₃Si₂O₁₄crystals with ordered langasite structure

A bulk of single crystals Ca₃Ta(Al_0.9Ga_0.1)₃Si₂O₁₄(CTAGS) with ordered langasite structure in which 90% of gallium was replaced by aluminum was successfully grown by the Czochralski technique. X-ray power diffraction (XRPD) studies confirm that the CTAGS crystals possess a langasite structure. The lattice parameters are a=8.053 Å, c=4.938 Å, and V=277.36 ų. High resolution X-ray diffraction (HRXRD) analysis demonstrates that CTAGS single crystals are free of low-angle boundaries. The piezoelectric coefficient d₁₁, dielectric constant ε₁₁/ε₀, dielectric loss electromechanical coupling factor k₁₂, mechanical quality factor Q and electric resistivity of X-cut plate of CTAGS were measured from room temperature up to 900 °C. d₁₁, ε₁₁/ε₀and s11E were found to increase from 3.99 pC/N to 5.67 pC/N, from 13.7 to 15.4 and from 7.92 pm²/N to 8.87 pm²/N, respectively. In addition, the as-growth crystal is transparent in the wavelength range of 300-3200 nm and the highest transmittance exceeds 90%.