High-dielectric-constant and low-loss microwave dielectric in the (1 − x)La(Mg0.5Ti0.5)O3–x(Ca0.8Sr0.2)TiO3 solid solution system

Abstract The microwave dielectric properties and microstructures of (1 −  x )La(Mg 0.5 Ti 0.5 )O 3 – x (Ca 0.8 Sr 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 0.5 Ti 0.5 )O 3 –0.5(Ca 0.8 Sr 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.