Formation characteristics of calcium stannate from SnO2 and CaCO3 synthesized in CO-CO2 and air atmospheres

Calcium stannate (Ca2SnO4) is a common dielectric ceramic that is generally prepared by a high-temperature solid-state method in an air atmosphere with a roasting temperature of more than 1300 °C. In this study, Ca2SnO4 was much more easily synthesized in a CO-CO2 atmosphere at a relatively low temperature of less than 1000 °C for 30 min. We comparatively investigated the formation behavior and microwave dielectric properties of Ca2SnO4 synthesized from tin dioxide (SnO2) and calcium carbonate (CaCO3) by a solid-state method in air and CO-CO2 atmospheres using X-ray diffraction, scanning electron microscopy, inductively coupled plasma atomic emission spectroscopy, and vector network analysis. The formation behavior of calcium stannate indicated that the reactions between SnO2 and CaCO3 in CO-CO2 and air atmospheres were both controlled by three-dimensional diffusion. In a CO-CO2 atmosphere, the reaction had a higher reaction rate constant (k) and lower apparent activation energy (E). In addition, Ca2SnO4 was synthesized by a low-temperature solid-state method in a CO-CO2 atmosphere. The results indicated that Ca2SnO4 ceramics had a higher dielectric constant and lower dielectric tangent loss than those synthesized by the high-temperature solid-state method in air. However, the synthesis temperature and time were reduced by more than 300 °C and 8 h, respectively.