Microwave Dielectric Properties of CaTiO ₃ ‐CaAl _1/2 Nb _1/2 O ₃ Ceramics Doped with Li ₃ NbO ₄

Abstract

The microwave dielectric properties of CaTi 1− x (Al 1/2 Nb 1/2 ) x O 3 solid solutions (0.3 ≤ x ≤ 0.7) have been investigated. The sintered samples had perovskite structures similar to CaTiO 3 . The substitution of Ti 4+ by Al 3+ /Nb 5+ improved the quality factor Q of the sintered specimens. A small addition of Li 3 NbO 4 (about 1 wt%) was found to be very effective for lowering sintering temperature of ceramics from 1450–1500° to 1300°C. The composition with x = 0.5 sintered at 1300°C for 5 h revealed excellent dielectric properties, namely, a dielectric constant (ɛ r ) of 48, a Q × f value of 32 100 GHz, and a temperature coefficient of the resonant frequency (τ f ) of −2 ppm/K. Li 3 NbO 4 as a sintering additive had no harmful influence on τ f of ceramics.