BaY16Si4O33 containing Ba(SiO4)(4) orthosilicates

Single crystals of a new quaternary oxide, barium hexadecayttrium tetrasilicon tritriacontaoxide, BaY16Si4O33, were obtained from a melt-solidified sample prepared by heating a mixture of BaCO3, Y2O3, and SiO2 at 2073 K. X-ray crystal structure analysis revealed that Ba(SiO4)(4) orthosilicate clusters in which a Ba atom is surrounded by four SiO4 tetrahedra were isolated in a framework composed of Y and O in the structure of BaY16Si4O33. The dielectric constant measured for polycrystalline ceramics of BaY16Si4O33 sintered at 1953 K was 13 (298 K, 1 MHz), and the thermal expansion coefficient was 8.70 x 10(-6) K-1 (298-873 K), which are close to the values previously reported for Y2O3.