Electrical properties and scaling behaviour of Sm^3 + doped CaF₂-bismuth borate glasses

Abstract

The electrical properties for 20Bi₂O₃–60B₂O₃ (20−x)–CaF₂–xSm₂O₃ glasses (0 ≤ x ≤ 2) were measured in the temperature range 297 K up to 629 K and in the frequency range 0·1–100 kHz. The d.c. and a.c. conductivity values and the dielectric loss (tan δ) values were found to increase with increasing Sm₂O₃ content, whereas the activation energy of conductivities and the dielectric constant decreased. These results were attributed to the introduction of the rare earth ions; promote the formation of a high number of non-bridging oxygen atoms, which facilitate the mobility of charge carriers. The frequency dependence of the a.c. conductivity follows the power law σ _ac(ω) = Aω ^s. The frequency exponent (s) values (0·64 < s < 0·8) decrease with increasing temperature. This suggested that the a.c. conduction mechanism follows the correlated barrier hopping model (CBH). The dielectric constant (ε ^′) and dielectric loss (tan δ values) were found to increase with increasing temperature and increasing Sm₂O₃ concentration in the glass. The a.c. conductivities as a function of frequency at different temperatures of a given glass superimposed onto a master curve (Roling scaling model). Furthermore, we have performed to scale the data as a function of composition. Two master curves were obtained, which suggested that there are differences in dominant charge carriers between glasses having Sm₂O₃ concentration ≥1 and glass of Sm₂O₃ concentration <1.