Microstructure and Microwave Dielectric Properties of xCa(Al0.5Nb0.5)O3+(1-x)SrTiO3 Solid Solutions

The crystal structure evolution and microwave (MW) dielectric properties of xCa(Al0.5Nb0.5)O-3+(1-x)SrTiO3 (xCAN+(1-x)ST, 0 < x < 1.0, ) dielectric ceramics were investigated. X-ray diffraction patterns illustrated that a single perovskite solid solution could be formed between the two end members; however, minor amount of pyrochlore phase was also detected in the composition range of 0.5 < x < 0.9. With the increase of x value, the crystal structure gradually evolved from a simple Pm3m cubic to a monoclinic P2(1)/n space group with the octahedral tilting and the B-site ordering structure transition subsequently developed. The MW dielectric properties of xCAN+(1-x)ST solid solutions were elaborately investigated and correlated to their crystal structures. The microscopic structure-related thermal parameters in the xCAN+(1-x)ST solid solution were analyzed in terms of the Claussius-Mossotti equation to reveal the original contributors in temperature coefficients. Temperature coefficient-compensated ceramic could be obtained in the xCAN+(1-x)ST system in the range of 0.5 < x < 0.6. When sintered at 1500 degrees C for 4 h, a dielectric constant epsilon(r) of 37.32, a Qf product of 25 430 GHz, and a tau(f) value of -22.4 ppm/degrees C MW dielectric ceramic could be obtained in the 0.6Ca(Al0.5Nb0.5)O-3+0.4SrTiO(3) composition.