Crystalline Phases and Dielectric Properties of Crystallized Glasses in the (Ca, Sr, Ba) O-Al2O3-SiO2-TiO2 System.

Abstract

The relationship between crystallized phases and dielectric properties of crystallized glasses in the (Ca, Sr, Ba)O-Al2O3-SiO2-TiO2 system was investigated. Powder sample of 0.386(Ca0.189, Sr0.518, Ba0.293)O⋅0.094Al2O3⋅0.520SiO2⋅0.121TiO2 glass (sample Ti-G) was used for this study and powder samples of 0.386(Ca0.189, Sr0.518, Ba0.293)O⋅0.094Al2O3⋅0.520SiO2 glass (sample G) and mixture of sample G with 0.121TiO2 (sample G/Ti) were used to obtain reference data. These powders were pressed in disks and sintered at 850, 900 and 950°C for 2h. Crystalline phases of (Ca, Sr, Ba)Al2Si2O8 (AS) and (Ca, Sr, Ba)2TiSi2O8 (TS) precipitated in sample Ti-G and only AS phase precipitated in sample G at 950°C. Dielectric constant and temperature coefficient of capacitance (TCC) were measured for each sintered sample. The TCC values of the samples Ti-G and G (sintered at 950°C) were negative and positive values, respectively. These experimental results clearly show that the negative TCC value of sintered Ti-G samples is mainly due to the presence of TS phase. The dielectric constant and the TCC of the TS phase, estimated by empirical equations involving the rule of mixture, were 13.2 and -241ppm/°C, respectively.