Preparation and dielectric properties of (Ca0.61,Nd0.26)TiO3nanoparticles by a sol–gel method

Abstract

Ultrafine (Ca_0.61,Nd_0.26)TiO₃ powder was synthesized by a sol–gel method. The X-ray diffraction result of the powder showed the presence of an orthorhombic GdFeO₃-type perovskite phase with minute amounts of CaCO₃. As the heat-treatment temperature of the xerogel was increased to 800 °C, CaCO₃ disappeared completely. The average particle size calculated from the transmission electron microscopy micrograph of the powder was 5–10 nm. Compared with conventional solid-state method (1400 °C for 4 h), the ultrafine (Ca_0.61,Nd_0.26)TiO₃ powder can be sintered compactly at relatively low temperature (1200 °C for 2 h). Microwave dielectric characteristics of (Ca_0.61,Nd_0.26)TiO₃ ceramics fabricated from nanoparticles prepared via the sol–gel process were improved. At 1200 °C, very dense ceramics with uniform grains and good dielectric properties of dielectric constant (ε) = 90.2, Q × f value (the product of quality factor Q and frequency f) = 25 200 GHz, and a temperature coefficient of resonant frequency (τ_f) = +243ppm °C⁻¹ were achieved.