Relaxor-like Dielectric Behavior in Stoichiometric Sillenite Bi₁₂SiO₂₀

A combination of fixed frequency dielectric measurements (10 3 to 10 6 Hz) and impedance spectroscopy reveal evidence of (nonferroelectric) relaxor-like behavior in the temperature range ∼600–750 K for the stoichiometric sillenite phase Bi 12 SiO 20 (space group I 23, a = 10.1034(5) Å). Variable temperature Raman Spectroscopy reveals significant changes associated with the Bi–O framework vibrations, and the relaxor-type behavior is attributed to noncorrelated local dipole moments associated with the BiO 5 E ( E = 6s 2 lone pair) units in the framework. Sillenites, therefore, represent another family of Bi-based oxides to exhibit relaxor-like dielectric behavior.