INFLUENCE OF THERMAL STRESS ON QUALITY FACTOR OF THE LAYERED Mg0.93Ca0.07TiO3-(Ca0.3Li0.14Sm0.42)TiO3 SYSTEM PREPARED BY SPARK PLASMA SINTERING

The layered Mg0.93Ca0.07TiO3-(Ca0.3Li0.14Sm0.42)TiO3 ceramics were prepared by the spark plasma sintering technique, and the effect of thermal strain on the microwave dielectric properties was investigated. Neither the secondary phase nor the active ionic diffusion through the interface between the two systems was found, which resulted from the rapidly increasing temperature and short sintering time of the spark plasma sintering. The dielectric constant of the specimen was changed by the dielectric mixing rule in addition to the relative density that was increased up to 98% of the theoretical density with an increase of sintering temperature and time. The quality factor showed a high value of 8650 GHz compared with that of 7900 GHz of the layered structure specimens with similar relative densities sintered under atmospheric pressure. The quality factor decreased with an increase of induced thermal strain to each dielectric layer, which resulted from the difference in thermal expansion coefficient between the two systems during the cooling process after sintering. 22 refs.