Characterization of CaTiO3-NdAlO3 dielectric ceramics

An X-ray analysis of the (1−x)CaTiO3–xNdAlO3 tie line revealed solid solubility across the entire compositional range. For x<0.85 the crystal structure of the solid solution is that of the orthorhombically distorted perovskite, which is also the structure of pure CaTiO3, whereas solid solutions with x>0.90 exhibit the trigonal structure, characteristic of pure NdAlO3. With the increase in x the permittivity, the temperature coefficient of resonant frequency and the dielectric losses decrease. Ceramics based on the 0.7CaTiO3–0.3NdAlO3 solid solution exhibit τf≈0 ppm/K, εr=44 and a Q-value that varies between 30000 and 45000 GHz depending on the cooling rate after the sintering. A microstructural analysis revealed the presence of twin related domains, antiphase boundaries and two types of inclusions rich in Al: hexagonal CaAl12O19-based inclusions and the spinel MgAl2O4, which results from the Mg-based impurities.