High-dielectric-constant and low-loss microwave dielectric in the (1 − x)La(Mg 0.5Ti 0.5)O 3– x(Ca 0.8Sr 0.2)TiO 3 solid solution system

Abstract

The microwave dielectric properties and microstructures of (1 − x)La(Mg 0.5Ti 0.5)O 3– x(Ca 0.8Sr 0.2)TiO 3 ceramics, prepared by a mixed oxide route, have been investigated. The forming of solid solutions was confirmed by the XRD patterns and the measured lattice parameters for all compositions. A near zero τ f was achieved for samples with x = 0.5, although the dielectric properties varied with sintering temperature. The Q × f value of 0.5La(Mg 0.5Ti 0.5)O 3–0.5(Ca 0.8Sr 0.2)TiO 3 increased up to 1475 °C, after which it decreased. The decrease in dielectric properties was coincident with the onset of rapid grain growth. The optimum combination of microwave dielectric properties was achieved at 1475 °C for samples where x = 0.5 with a dielectric constant ɛ r of 47.12, a Q × f value of 35,000 GHz (measured at 6.2 GHz) and a τ f value of −4.7 ppm/°C.