Lattice structure and microwave dielectric properties of [Mg0.5Si0.5]3+-doped LiAlO2 solid solution

Microwave dielectric properties of low-permittivity LiAl1-x(Mg0.5Si0.5)(x)O-2 (LAMS) (x=0.02-0.2) ceramics synthesised through solid-state reaction route were investigated. All compositions show pure LiAlO2 phase with a P4(1)2(1)2 space group at x0.18. Microstructure and relative permittivity (epsilon(r)) were greatly affected by the partial substitution of [Mg0.5Si0.5](3+) for Al3+ site. Bond energy decreased with increasing x value, thereby increasing the temperature coefficient of resonant frequency ((f)) in the negative direction. Finally, the optimum microwave dielectric properties of LAMS (x=0.02) sample were obtained at 1300 degrees C with epsilon(r)=6.17, Qxf=53,300GHz and (f)=-129ppm/degrees C. Then CaTiO3 was added to the LAMS (x=0.02) material to adjust the (f) value to near zero.