Effects of Addition of Glasses Containing BaO and TiO<sub>2</sub> on Properties of BaTiO<sub>3</sub> Ceramics

Abstract

In order to extend to firing range and also improve the dielectric properties of BaTiO3 ceramics, glass powders of the BaO-TiO2-SiO2-Al2O3 system were added as the binding agent in a total amount of 5 to 15wt% to BaTiO3 crystal powders. Compositions of the glasses prepared were in ranges of 40 to 55 BaO, 22 to 33 TiO2, 5 to 12 SiO2 and 5 to 18 Al2O3wt%. The mixtures of crystal and glass powders (particle size: both less than 325 mesh) were formed by dry-pressing, being subjected to the measurement of firing range (from the temperature corresponding to the water-absorption-zero to the deformation temperature). Measurements of dielectric properties were made at room temperature with frequency of 1Mc/sec, of the mixtures fired at 1200° to 1400°C for 60 min.The results obtained are summarized as follows: 1) The firing range of the pressed compacts extends by about 100° to 200°C by addition of the glass powders rich in BaO and TiO2. 2) Dielectric properties of the sintered specimens become less sensitive to their firing temperature by addition of the glasses. 3) Dielectric constant of the sintered specimens are much affected by the composition of glasses added; the MgO component in glass is effective to increase the dielectric constant of the specimens. 4) Addition of the glass powders together with MgF2 crystal powders most increases the dielectric constant of the specimens. 5) Effects of the addition of glass powders can be reasonably explained on the basis of the electron microscopic observation of the microstructure of the specimens.