Structure-Dependent Microwave Dielectric Properties and Middle-Temperature Sintering of Forsterite (Mg1-xNix)2SiO4 Ceramics

The crystal structure, microstructure, and microwave dielectric properties of forsterite‐based (Mg1–xNix)2SiO4 (x = 0.02–0.20) ceramics were systematically investigated. All samples present a single forsterite phase of an orthorhombic structure with a space group Pbnm except for a little MgSiO3 secondary phase as x > 0.08. Lattice parameters in all axes decrease linearly with increasing Ni content due to the smaller ionic radius of Ni2+ compared to Mg2+. The substitution of an appropriate amount of Ni2+ could greatly improve the sintering behavior and produce a uniform and closely packed microstructure of the Mg2SiO4 ceramics such that a superior Q × f value (152 300 GHz) can be achieved as x = 0.05. The τf value was found to increase with increasing A‐site ionic bond valences. In addition, various additives were used as sintering aids to lower the sintering temperature from 1500°C to the middle sintering temperature range. Excellent microwave dielectric properties of εr~6.9, Q × f~99800 GHz and τf~−50 ppm/°C can be obtained for 12 wt% Li2CO3‐V2O5‐doped (Mg0.95Ni0.05)2SiO4 ceramics sintered at 1150°C for 4 h.