Synthesis and structure of new phases of the Am?1Bi2BmO3m+3 (m = 2) type

Three polycrystalline bismuth-containing layered perovskite-like oxides are synthesized by high-temperature solid-state reactions. One of these compounds was described previously, namely, Bi₃Ti_1.5W_0.5O₉, for which the unit cell parameters a = 5.372(5) Å, b = 5.404(4) Å, and c = 24.95(2) Å are determined in this study. The other two compounds, namely, Na_0.75Bi_2.25Nb_1.5W_0.5O₉ with the unit cell parameters a = 5.463(1) Å, b = 5.490(7) Å, and c = 24.78(0) Å and Ca_0.5Bi_2.5Ti_0.5Nb_1.5O₉ with the unit cell parameters a = b = 3.843(2) Å and c = 24.97(6) Å, are synthesized for the first time. The compositions of these compounds are based on the composition of the well-known compound Bi₃TiNbO₉ with a high Curie temperature (T _C = 1223 K), in which bismuth, niobium, and titanium atoms are partially or completely replaced by other atoms. The experimental and calculated interplanar distances determined from the X-ray diffraction patterns of the studied compounds are presented. __________ Translated from Kristallografiya, Vol. 50, No. 1, 2005, pp. 59–64. Original Russian Text Copyright ? 2005 by Geguzina, Shuvaev, Shuvaeva, Shilkina, Vlasenko.