Influence of CuO on crystallization and electrical properties of B2O3-Bi2O3-GeO2- CaF2 glass system for thermoelectronic applications

Germanium bismuth-borate glasses with varying concentration of CuO of [(55-x)B2O3-20Bi2O3-5GeO2-20CaF2:xCuO] composition were prepared with melt-quenching method. The structure and thermal behavior of the samples were described through DTA, XRD, FTIR spectroscopy. The low energy of formation phases Bi44GeO68, CaGeO3 and CuGe3O9 were crystallized by the incorporation of CuO. [BO3] and [BO4] units are the main building groups of the glass matrix with some sharing of BiO6 and GeO4 units as FTIR analysis indicated. The electrical and dielectric characteristics were studied by broadband dielectric spectroscopy upon a wide-ranging of frequency (10-1 -107 Hz) and at temperatures 240 and 330 K. The heat-treated samples reveal higher conductivity than glass, by about three decades, at 330 K as the ratio of CuO increases to be in the range of semiconducting materials. The enhancement of dielectric properties of heat-treated samples over considered glass samples makes them better choices for the energy storage glass-dielectrics.