Microstructure and dielectric properties of Ba_xY₂₆Si₁₆O_71+x (x ≈ 10.2) ceramics prepared using a planetary ball mill

Abstract

BaCO₃, Y₂O₃ and SiO₂ powders weighed at Ba:Y:Si molar ratios of x:26:16 with x = 9.0–14.0 were mixed in a planetary ball mill, compacted, and calcined at 1300 °C for 12 h. The calcined compacts were reground in a planetary ball mill and recompacted to form disk-shaped powder compacts that were then heated at 1600 °C for 2 h. X-ray diffraction measurements revealed that the ceramic disks were mainly composed of the tetragonal oxide, Ba_xY₂₆Si₁₆O_71+x (x ≈ 10.2), with some secondary phases. A ceramic disk with the highest relative density of 96 % respect to the theoretical density of the tetragonal oxide was obtained at x = 10.8. The granular and elongated grains of the tetragonal oxide were contained in a matrix of fine oxide grains. The relative dielectric constant (ε_r) and dielectric loss (tan δ) measured for the ceramic disk at frequencies of 10 Hz and 1 MHz were 5410 and 0.07, and 380 and 0.44 at 25 °C, and 7000 and 0.08 and 3830 and 0.334 at 325 °C, respectively.