Optical and transport properties of xCuO•(1-x)Li2B4O7 glasses

The structure and transport properties of xCuO center dot(1-x)Li2B4O7 (CuLiB) glasses were studied as x was varied between 0 and 0.15. While the electrical resistivity has been observed to increase with increasing CuO fraction, the optical absorption spectra of CuLiB glasses exhibit the presence of both Cu+ and Cu2+. Raman spectra demonstrate decreasing polymerization of borate tetrahedra and BO3 triangles with increasing Cu concentration leading to a denser glass and confirm that Cu may be present in the form of symmetrical CuO6 octahedra with little to no Raman activity. Among other properties determined, glass transition temperature and density have been observed to increase with increasing CuO content, along with a decrease in molar volume. This increased density combined with lower Li content, as CuO is added to the glass, results in reduced electrical conductivity. Both ionic and small polaronic conduction is observed.