Elastic, Piezoelectric, and Dielectric Constants of Bi12 GeO20

In order to resolve conflicting published results concerning the values of the elastic, piezoelectric, and dielectric constants of Bi₁₂GeO₂₀, an exhaustive study of this material has been made. Over 45 samples of material grown by three independent sources were tested. The piezoelectric constant was determined using three different techniques. In addition, the first accurate measurements of the dielectric constant of Bi₁₂GeO₂₀ at microwave frequencies have been made. Recommended values of the material constants are as follows: $c_{11}^E{\text{=1.28×10}}^{11}\hspace{0.17em}{\mathrm{N/m}}^2$ , $c_{12}^E{\text{=0.305×10}}^{11}\hspace{0.17em}{\mathrm{N/m}}^2$ , $c_{44}^E{\text{=0.255×10}}^{11}\hspace{0.17em}{\mathrm{N/m}}^2$ , e₁₄ = 0.99 C/m², and ${\epsilon }_{11}^S{\text{=34.2×10}}^{\text{−11}}\hspace{0.17em}\mathrm{F/m}$ .