Microwave Dielectric Properties of Ca_0.8Sr_0.2TiO₃–Li_0.5Nd_0.5TiO₃ Ceramics with Near-Zero Temperature Coefficient of Resonant Frequency

The microstructure and microwave dielectric properties of (1-x)Ca_0.8Sr_0.2TiO₃–xLi_0.5Nd_0.5TiO₃ (x=0–1.0) were investigated. X-ray diffraction and scanning electron microscopy results show that all samples exhibit a single perovskite structure and a dense microstructure. The order of A-site cations was observed in the structure of samples with x≥0.80 in the X-ray diffraction pattern. The dielectric constant decreased with an increase in x. The quality factor first decreased with an increase in x and then increased slightly with a further increase in x. The temperature coefficient of resonant frequency decreased from high positive values to negative values as x increased. A near-zero temperature coefficient of resonant frequency (-2.75 ppm/°C) was obtained at x=0.87. Optimized microwave dielectric properties were estimated to be (ε_r=111.6; Q×f=2013 GHz; τ_f=-2.75 ppm/°C) at x=0.87.