Effect of La_2O_3-Dopant on Microstructure and Microwave Dielectric Properties of CaO-MgO-Nb_2O_5-TiO_2 System Ceramics

摘要

La2O3-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 La3+ ions. The results show that the replacement of Ca2+ by La3+ at A-site of the ceramics can increase the quality factor Q·f value as well as the temperature coefficient of resonant frequency τf and decrease the dielectric constant εr. With increase of La3+ contents, the dielectric constant decreases from 57 to 35 and Q·f value increases from 33400 GHz to 35000 GHz （at 7.6 GHz）. Meanwhile, the temperature coefficient of resonant frequency is improved towards near zero. The dielectric properties of these compounds are related to octahedra tilting due to deficient vacancies at A-site.