Sintering Behavior and Microwave Dielectric Properties of (Ca, La)(Ti, Al)O3 Ceramics

The dielectric and sintering properties of (1- x )CaTiO 3 – x LaAlO 3 were investigated. The greater the amount of LaAlO 3 , which has a lower sintering temperature than CaTiO 3 , the higher the relative density is obtained. As x increased in (1- x )CaTiO 3 – x LaAlO 3 , the following phase transformation occurred: orthorhombic ( x ≤0.4) →pseudocubic ( x =0.5) →rhombohedral ( x ≥0.6). The microwave dielectric properties of ε r =37, Q · f 0 =47,000 (at 7 GHz), and τ f =5 ppm/°C were obtained at 0.65CaTiO 3 –0.35LaAlO 3 . Also, various compounds of low melting point were added to 0.5CaTiO 3 –0.5LaAlO 3 in order to decrease the sintering temperature. When 3 wt% of 0.97Bi 2 O 3 –0.03Al 2 O 3 or 0.76Bi 2 O 3 –0.24NiO as sintering additive was added, the sintering temperature was lowered from 1600°C to 1450°C, and the relative dielectric constant ( ε r ) and the temperature coefficient of the resonant frequency (τ f ) were not changed, whereas the Q · f 0 values were lowered by about 15% and 34%, respectively.