Lead titanate glass-ceramics derived from a silicate-based melt

摘要

Glass composition 39PbO-lBaO-25TiO_2-9.8Al_2O_3-24.2SiO_2-lB_2O_3 (mol percent) crystallized on heat treatment at >= 600 deg C to form glass-ceramics whose majority phase was PbTiO_3 (PT). At 600 deg C, nano-size PT crystals (-20-50 nm) with a da ratio of 1.000(1) were observed, but as heat-treatment temperature increased to 1000 deg C, the crystal size and da ratio increased to approx 1.2 mu m and 1.056(4), respectively. Permittivity measurements as a function of temperature revealed a broad peak at approx 400 deg C associated with the nanocrystalline PT crystals, but it sharpened and increased in temperature as heat treatment temperature increased to 1000 deg C. The causes of peak broadening and shift of T_c are believed to be due to either clamping of PT crystals by glass matrix, finite size effects due to their intrinsically small size, or the incorporation of dopant impurities such as Al, Si, or Ba ions in the PT phase.