Structural and Dielectric Properties of RE3+, B3+ co-doped (RE3+=Sm3+, Dy3+) BaTa2O6 Tetragonal Tungsten Bronze-Type Ceramics

Abstract

In this paper, the effect of boron doping on dielectric properties was investigated using BaTa2O6:xSm3+, yB3+ (x=5 mol%, y= 0, 5, 15, 30, 50, 70, 100 mol%) and BaTa2O6:xDy3+, yB3+ (x=10 mol%, y= 0, 5, 15, 30, 50, 70, 100 mol%) tungsten bronze ceramics fabricated by the conventional solid-state synthesis. XRD (X-ray diffraction) results revealed a single BaTa2O6 phase with space group P4/mbm (127) for both series. Additionally, in both series, there was an increase in crystallite sizes and cell parameters with increasing B3+ concentration. SEM (scanning electron microscopy) examinations indicated that the increase of boron promoted grain growth and grain elongation. In impedance results, in both series, increasing boron concentration up to 100 mol% increased the dielectric constant. Moreover, the presence of boron was associated with a relaxing transition in the B-site substitution of RE3+ (RE=Sm, Dy) ions and a contribution to the dielectric permittivity, while the increase in tetragonality or c/a ratio for both series was ascribed to the increase in the ferroelectric Curie temperature. In both series, a decrease in dielectric loss (tan δ) occurred, which was explained by the increasing sintering temperature effect with increasing boron, reducing the mobility of oxygen vacancies.