Crystal structure and dielectric properties of (1-x)Ca0.61Nd0.26TiO3+xNd(Mg1/2Ti1/2)O3 complex perovskite at microwave frequencies

The crystal structure and microwave dielectric properties of (1-x)Ca0.61Nd0.26TiO3+xNd(Mg1/2Ti1/2)O-3 (0 <= x <= 1.0) solid solutions incorporated with 1 wt % CuO were investigated. Pure perovskite phases were formed in the whole composition range, and the crystal space group and unit cell volume of the perovskites were analyzed based on x-ray diffraction patterns. The configuration of octahedral tilting and the B-site ordering phase transition between x=0.9 and 1.0 were unambiguously assigned, respectively, to the corresponding superlattice diffractions. Moreover, the two important fingerprints A(1g) mode and F-2g mode in Raman spectra, associated with the evolution of short range ordering and long range ordering of B-site cations, respectively, were further investigated by employing the full width at half-maximum and their Raman shifts to determine the degree of B-site ordering and the crystal bond strength in the perovskites. The microwave dielectric constants, quality factors, and temperature coefficients of resonant frequency of the solid solutions were elaborately investigated and correlated with their crystal structures. The microscopic structure-related thermal parameters in the solid solution were calculated using the Claussius-Mossotti equation to determine the original contributors in the temperature coefficients. Temperature compensated tau(f) value ceramics could be obtained in the range of 0.3 < x < 0.5. When sintered at 1400 degrees C for 2.5 h, a dielectric constant epsilon(r) of 39.9, a quality factor product of 12 600 GHz, and a tau(f) of -25.3 ppm/degrees C microwave dielectric ceramic were obtained in 0.5Ca(0.61)Nd(0.26)TiO(3)+0.5Nd(Mg1/2Ti1/2)O-3+1 wt % CuO composition.