Ultra low loss (Mg1 − xCax)2SiO4dielectric ceramics (x = 0 to 0.15) for millimeter wave applications

Abstract (Mg 1 − x Ca x ) 2 SiO 4 dense ceramics (x ≥ 0.15) were prepared, and their microwave dielectric characteristics were investigated together with the structure evolution. The sintering temperature for Mg 2 SiO 4 ceramics was reduced significantly with Ca 2+ substitution. (Mg 1 − x Ca x ) 2 SiO 4 ceramics exhibited a small increase in dielectric constant ( ε r ) correlated with increased crystallite size, and ultra‐high quality factor Qf value was achieved throughout the compositional range. Temperature coefficient of resonant frequency ( τ f ) was considerably tuned from −70 ppm/°C to −33 ppm/°C, and this improvement was deeply linked with the decreased bond valance. At x = 0.075, (Mg 1 − x Ca x ) 2 SiO 4 ceramics exhibited the best combination of microwave dielectric characteristics: ε r = 7.2, Qf = 199,800 GHz at 26 GHz, τ f = −33 ppm/°C. The present ceramics could be expected as promising candidate of dielectric materials for millimeter wave applications.