Abstract
? 2022 Elsevier B.V.The glass ceramics of the composition PbO-B2O3-SeO2:Er2O3 (PBSE) doped with small concentrations of Au2O3 were synthesized. The results of detailed studies on various characterization techniques and also different spectroscopic investigations suggested that these glass ceramics are entrenched with Au2(SeO3)3 crystal phases and Au0 metallic particles (MPs). These studies further revealed increasing concentration of [SeO3]2- groups and Au0 metallic particles with the increase of Au2O3 content upto 0.075 mol%. Such [SeO3]2- groups are predicted to induce structural imperfections in the glass ceramic. Optical absorption (OA) and photoluminescence (PL) spectral studies also indicated increasing concentration of imperfections with increase of Au2O3 content. The dielectric viz, dielectric permittivity (ε′), electrical modulus (M), electrical impedance (Z) and a.c. conductivity (σac) spectra in the frequency (ω) region 4 Hz to 8 MHz and in the temperature (T) region 303–633 K of these glass ceramic samples were measured as functions of Au2O3 concentration. The dielectric permittivity (ε′) exhibited an increasing trend with Au2O3 concentration and it is ascribed to the increase in the magnitude of the space charge polarization (scp) due to the increase in the concentration of structural defects induced by [SeO3]2- units and Au0 metallic particles. The plots of electric modulus (M) with frequency and temperature exhibited dipolar relaxation phenomena. Such effects were analyzed further using Cole-Cole diagrams and the possible dipoles responsible for these effects were identified. A.C. conductivity (σac) exhibited increasing trend with the concentration of Au2O3 (up to 0.075 mol%) and such increase is attributed to the polaronic exchange between different structural groups of selenium oxide. The conduction mechanism is analyzed using polaronic tunneling effect in the middle frequency and high temperature regions, whereas in the lower temperature region QMT model seems to be applicable. Conclusions drawn from dielectric properties were found to be well in accordance with the results of spectroscopic properties.
NSTL
Elsevier