Synthesis and microwave dielectric properties of CaSiO3 nanopowder by the sol–gel process

The synthesis and microwave dielectric properties of CaSiO3 nanopowder by sol–gel method have been investigated in this paper. CaSiO3 nanoparticles with an average grain size of 50–60 nm were obtained by calcining the CaO–SiO2 xerogel that was prepared from Calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and tetraethylortho silicate (TEOS). Calcining the CaO–SiO2 xerogel at 1150 °C, the pseudowollastonite-CaSiO3 phase was completely formed. However, the main phase is not CaSiO3 or CaSi2O4 but SiO2 when calcining the mixture of SiO2 and CaCO3 at 1150 °C. Comparing with CaO–SiO2 ceramics prepared by solid-state process, the CaSiO3 ceramics made from nanopowders calcined at 1000 °C achieved more compact structure at the sintering temperature of 1320 °C, and then had excellent microwave dielectric properties: ɛr = 6.69, Qf = 25398 GHz.