Ferroelectricity in Bi_(26-x)M_xO_(40-δ) (M = Al and Ga) with the γ-Bi_2O_3 structure

摘要

We report on the dielectric properties of bismuth aluminate and gallate with Bi:Al(Ga) ratio of 1:1 and 12:1 prepared at high temperature and ambient pressure. These compounds crystallize in a noncentrosymmetric body-centered cubic structure (space group I23) with a ～ 10.18 A rather than in the perovskite structure. This cubic phase is related to the γ-Bi_2O_3 structure which has the actual chemical formula Bi_(24)~(3+)(Bi~(3+)Bi~(5+))O_(40-δ). In the aluminates and gallates studied by us, the Al and Ga ions are distributed over the 24f and 2a sites. These compounds exhibit ferroelectric hysteresis at room temperature with a weak polarization.