Evaluation of Structural and Dielectric Properties of Eu3+, B3+ co-doped Ba2GdMO6 (M=Nb, Ta) Double Perovskite Ceramics

Abstract

In the study, the structural and dielectric properties of Ba2GdMO6 (M=Nb, Ta) double perovskite ceramics produced with solid-state method were examined by co-doping xEu3+ and yB3+ (x=10 mol%, y=0, 5, 15, 30, 50, 70 and 100 mol%). XRD (X-ray diffraction) results of the ceramic samples exhibited a single-phase structure with cubic symmetry Fm-3m space group, while increasing B3+ concentration led to an increase in crystallite sizes and lattice parameters up to 50 mol% in both series. SEM (scanning electron microscopy) examinations revealed the presence of boron-supported grain growth and agglomeration in the grains of both series, and also a slight angularity occurred in grain shape at high B3+ concentrations. The dielectric constant (ε') of the ceramic samples in both series increased with increasing boron concentration up to 50 mol%, and it was approximately 33.5 and 35.4 at 20 Hz for the Ba2Gd1-xNbO6:xEu3+, yB3+ and Ba2Gd1-xTaO6:xEu3+, yB3+, respectively. The decrease in the dielectric constant after 50 mol% may be attributed to the presence of increased strain in the structure, as shown by the decrease in crystallite size. The increasing B3+ concentration caused a decrease in dielectric loss (tan δ) in both series, which was attributed to the suppression of oxygen vacancies due to the increased presence of B3+ and hence to a decrease in ionic conductivity and dielectric loss.