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Materials Data on La3Ga by Materials Project

La3Ga is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. La is bonded to eight equivalent La and four equivalent Ga atoms to form distorted LaLa8Ga4 cuboctahedra that share corners with twelve equivalent LaLa8Ga4 cuboctahedra, edges with eight equivalent GaLa12 cuboctahedra, edges with sixteen equivalent LaLa8Ga4 cuboctahedra, faces with four equivalent GaLa12 cuboctahedra, and faces with fourteen equivalent LaLa8Ga4 cuboctahedra. All La–La bond lengths are 3.49 Å. All La–Ga bond lengths are 3.49 Å. Ga is bonded to twelve equivalent La atoms to form GaLa12 cuboctahedra that share corners with twelve equivalent GaLa12 cuboctahedra, edges with twenty-four equivalent LaLa8Ga4 cuboctahedra, faces with six equivalent GaLa12 cuboctahedra, and faces with twelve equivalent LaLa8Ga4 cuboctahedra.

36 MATERIALS SCIENCE↗

High-Temperature Properties of Piezoelectric Langatate Single Crystals

Langasite type crystals belong to non-polar point group of 32 and do not show any phase transformations up to the melting temperature. Langatate (La3Ga(5.5)Ta(0.5)O14) demonstrates piezoelectric activity better than quartz and possesses attractive properties for high temperature sensors, resonators and filter applications. High-quality and colorless langatate crystals were grown by the Czochralski technique. The electromechanical and electrical properties of langatate crystals in different crystallographic directions were characterized at elevated temperature. The piezoelectric coefficient along x-axis was 7 pC/N as measured by a Berlincourt meter for a plate geometry with an aspect ratio of 10:1. The dielectric constant did not exhibit any significant temperature dependence (K33 approx. 21 at 30 C and K33 approx. 23 at 600 C). Loss tangent at 100 kHz remained <0.003 up to 300 C and <0.65 at 600 C. The dielectric properties along the y-axis were similar and its temperature dependence was analogous to the x-axis. Electromechanically, the inactive z-axis exhibited no resonance with K33 approx. 84 at room temperature, decreasing down to approx. 49 at 600 C. Resistivity of these crystals along x-axis decreased from approx. 6x10(exp 11) omega-cm at room temperature, to approx. 1.6x10(exp 6) omega-cm at 600 C.

Sehirlioglu, Alp↗