Structural and Dielectric Properties of the Mn-Doped BaO-Nd2O3-4TiO2 System

The effect of the Nd2O3 and TiO2 ratios on the microstructure, dielectric properties and quality factor (Q.fr) of the 1 wt% Mn-doped BaO-Nd2O3-4TiO2 system were investigated. The samples sintered at various temperatures were analysed by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and a network analyser at 3 GHz. The grains of the Nd2O3 poor composition MBN0.5T4 were more spherical, whereas the grains of the excess Nd2O3 composition MBN1.5T4 were spherical and rod-like. The grains of the TiO2 poor composition MBNT4 and the TiO2rich composition MBNT5 were more rod-like than spherical. The grain size increased with increasing sintering temperature. The BaNd2Ti5O14 phase was observed for compositions based on a BaO/Nd2O3 = 1 ratio. The composition that deviated from the BaO/Nd2O3 = 1 ratio was composed of a major phase, BaNd2Ti5O14, with some secondary phases, Nd2Ti2O7 and BaTi4O9. The formation of the secondary phases affects the density, dielectric properties and quality factor of the Mn-doped BBaO-Nd2O3-4TiO2 system. The dielectric constant varies from 35–85 with different Nd2O3 and TiO2 contents. Quality factor values of 4200 to 10500 (at 3 GHz) can be obtained by varying the Nd2O3 and TiO2 contents.