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

The microwave dielectric properties and microstructures of (1 - x)La(Mg0.5Ti0.5)O-3-x(Ca0.8Sr0.2)TiO3 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 tau(f) was achieved for samples with x=0.5, although the dielectric properties varied with sintering temperature. The Qxf value of 0.5La(Mg(0.5)Ti0.5)O-3-0.5(Ca0.8Sr0.2)TiO3 increased up to 1475 degrees 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 degrees C for samples where x=0.5 with a dielectric constant epsilon(r) of 47.12, a Qxf value of 35,000 GHz (measured at 6.2 GHz) and a tau(f) value of -4.7 ppm/degrees C. (C) 2010 Elsevier B.V. All rights reserved.