Effect of Rare Earth Oxides on the Microstructure and Microwave Dielectric Properties of CaO-MgO-Nb_2O_5-TiO_2 System Ceramics

摘要

La2O3 and SrO-doped CaO-MgO-Nb2O5-TiO2 system ceramics were prepared by solid-state ceramic technique. The microstructure and microwave dielectric properties of CaO-MgO-Nb2O5-TiO2-La2O3 ceramics can be adjusted by varying the amount of La 3+ or Sr 2+ ions respectively. The replacement of Ca 2+ by La 3+ at A-site of the ceramics increases the quality factor Q value （at 7.6 GHz） as well as the temperature coefficient of resonant frequency τf and decreases the dielectric constant εr and the substitution of Sr 2+ at A-site in this ceramics system exhibits opposite characteristics. The microwave properties of La 3+,Sr 2+-doped CaO-MgO-Nb2O5-TiO2 system ceramics depend on the degree of octahedral distortion inside materials.