Characterization of low loss CoTiNb2O8 microwave dielectric ceramics based on the complex bond theory

The tetragonal-structured CoTiNb2O8 was prepared by the conventional solid-state method. Morphology, crystal structure and microwave dielectric properties of the ceramics were investigated by means of scanning electron microscope and X-ray diffraction. Single-phase CoTiNb2O8 could be obtained in the temperature range of 1100–1200 °C with the space group of P42/mnm. The dielectric constant and quality factors gradually increased with the increase of apparent density. The τf values were shifted toward zero with the increase of sintering temperature. Complex bond theory was reported for the first time to characterize the correlations between crystal structure and microwave dielectric properties. Typically, the saturated samples sintered at 1150 °C exhibited excellent microwave properties with εr value of 66.41, Q·f value of 10,153 GHz and τf value of 25.56 ppm/°C.