Dielectric properties of a-site deficient perovskite-type lanthanum-calcium-titanium oxide solid solution system [(1 − x)La23TiO3 − xCaTiO3 (0.1 ≤ x ≤ 0.96)]

Solid solution system of the double perovskite La23TiO3 and the GdFeO3-type perovskite CaTiO3, (1 − x)CaTiO3 — xLa23TiO3, has been prepared to investigate the crystal structure and the dielectric properties. In this system, the structure changed from pseudo-cubic perovskite to tetragonal double perovskite at x ≈ 0.7, and to orthorhombic double perovskite at x ≈ 0.9. Microwave dielectric measurement showed a decrease in dielectric constant and temperature coefficient of the resonant frequency and an increase in Q value with increasing x. The sample with x = 0.96 showed excellent microwave characteristics, especially high Q(2700) along with high εr(90) at 10 GHz. In the low frequency dielectric measurement, dielectric relaxation could be observed in the composition range x ≤ 0.3. The dielectric relaxation showed strikingly different behaviors depending on the annealing process in oxygen after sintering.