Phase and Microstructure Evaluation and Microwave Dielectric Properties of Mg1−x Ni x SiO3 Ceramics

The ceramics were prepared using the solid-state reaction method and their phase, microstructure and microwave dielectric properties were investigated. A single-phase clinoenstatite system with monoclinic structure (space group P2 1 /c) was confirmed through x-ray diffraction (XRD) analysis for the compositions with x  ≤ 0.1. The compositions with x  ≥ 0.15 contain SiO 2 and (Mg 1− x Ni x ) 2 SiO 4 phases only as confirmed from the XRD data of their sintered samples. The unit cell volume was decreased while the theoretical density was increased with increase in x from 0 to 0.1. A decrease in dielectric constant ( ε r ) while an increase in unloaded quality factor multiplying the resonant frequency ( Q u f o ) and temperature coefficient of resonant frequency ( τ f ) was observed with increase in Ni content from 0 to x  = 0.1. In the present study, ε r  ∼ 6.10, Q u f o  ∼ 118,702 GHz and τ f  ∼ −10 ppm/°C was achieved for the composition with x  = 0.1 sintered at 1425°C for 9 h. The material is a good candidate for millimeter wave applications.