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Electrical properties of beryllium-alumino-tellurite glasses and glass–ceramics doped with iron ions were studied using impedance spectroscopy. The conductivity was measured over a wide frequency range from 10 mHz to 1 MHz and the temperature range from 213 to 473 K. The D.C. conductivity values showed a correlation with the Fe-ion concentration and ratio of iron ions on different valence states in the samples. On the basis of Jonscher universal dielectric response the temperature dependence of conductivity parameters were determined and compared to theoretical models collected by Elliott. In glasses, the conduction process was found to be due to the overlap polaron tunneling while in glass–ceramics the quantum mechanical tunneling between semiconducting crystallites of iron oxides is proposed. The D.C. conductivity was found not to follow Arrhenius relation. The Schnakenberg model was used to analyze the conductivity behavior and the polaron hopping energy and disorder energy were estimated. Additionally, the correlation between alumina dissolution and basicity of the melts was observed.

The novel \\(Sr_5Pb_3ZnO_{12}\\) oxide was synthesized by the solid-state reaction method. The crystal structure was studied by means of the powder x-ray diffraction Rietveld method and was found to be similar to 3 other previously known \\(Sr_5Pb_3MO_{12}\\) compounds (M = Co, Ni, Cu). Crystals of several hundred microns in size of the new phase were grown in molten sodium chloride and imaged using confocal optical and scanning electron microscopy. Electrical properties were studied using the impedance spectroscopy technique. It was found that \\(Sr_5Pb_3ZnO_{12}\\) is a dielectric material with rather high relative permittivity (\\(\\epsilon_r\\) = 22 at 300K) and with activation energy of the dielectric relaxation process \\(E_A\\) = 0.80(4) eV. The heat capacity studies reveal the Debye temperature \\(\\Theta_D\\) = 324(1) K.