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 × 10^-6 K^-1 (298-873 K), which are close to the values previously reported for Y₂O₃. [ABSTRACT FROM AUTHOR]