Optical and electrical studies of borosilicate glass containing vanadium and cobalt ions for smart windows applications

Borosilicate glass with different concentrations of vanadium and cobalt of the composition (mol%) 40 Na2B4O7- 40 SiO2- (20-x) V2O5- x Co2O3, with x=0, 1, 3 and 5 mol% were prepared by melt quenching technique at 1373 K and investigated by X-ray diffraction (XRD) and FTIR spectroscopy. Optical properties of the obtained borosilicate glasses in the UV-vis range were also investigated. Urbach theory has been used to analyze the optical data. The dc electrical conductivity was investigated for all samples in the temperature range from 298 K to 700 K. The ac electrical conductivity was measured in the frequency range from 50 Hz to 2 MHz from 298 to 523 K. Guntini's theory has been used to analyze the electrical data. It was found that Urbach energy decreases with the increase of vanadium content, the sample with x=0 shows the highest absorption in the visible and IR region and an electrical conductivity in the order of 10−2 Scm−1. The frequency exponent was calculated. A semiconducting behavior has been assessed for the studied glasses. The sample with x=0 has the highest IR absorption, the highest conductivity, at 323 K at different frequencies, and the lowest activation energy; these features are promising for smart windows applications.