Structural and electrical properties of zinc tantalum borate glass ceramic

In this work we have synthesized ZnO–Ta₂O₅–B₂O₃ glass ceramics with different concentrations of Ta₂O₅. The prepared samples were characterized by XRD, SEM and DSC techniques. The results of these studies indicated that the samples are embedded with well defined randomly distributed crystalline phases with Zn₃Ta₂O₈ as the predominant one. The volume fraction of the crystallinity seemed to be increasing with increase of Ta₂O₅ content. The lattice parameters of this crystal phase and the optical band gap were evaluated theoretically using generalized gradient approximation (GGA) and also the local density approximation (LDA). The obtained results were compared with experimental values. The analysis of the results of IR and Raman spectroscopic studies indicated that the degree of polymerization of glass network increased with increase in the concentration of crystallizing agent (Ta₂O₅ ) up to 3.0 mol%. To evaluate the insulating strength of the glass ceramics we have studied the dielectric properties over broad ranges of frequency (100 Hz −1 MHz) and temperature (100–370 K) and also dielectric breakdown strength. The quantitative analysis of these results coupled with the results of spectroscopic studies indicated that the glass crystallized with 3.0 mol% of Ta₂O₅ possesses high insulating strength.