A comparative of structural, optical, mechanical and electrical properties of alkaline earth metal substituted tellurite glasses

Abstract

In the present work, the glass systems 0.70TeO2–0.30MO and 0.65TeO2–0.35MO (M = Ba, Sr) were prepared and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, UV–vis spectroscopy and differential scanning calorimetry. The structural studies show that amorphous alkaline tellurite glasses are made up of vibrational units of molecular water group, hydroxyl bonding, symmetrical stretching vibration of Te–Oax bonds in the deformed TeO4 and stretching and bending vibration of Te–O–Te linkages in TeO4/TeO3 + d polyhedra/TeO3. In the X-ray diffractograms, shifting of amorphous peak was observed towards higher angle side with the strontium substitution in comparison to barium substitution due to lower ionic radii. The optical band gap of investigated glasses was found to lie in the range 2.94–3.31 eV and was found to be lower in SrO added glasses than that of BaO added glasses. This may be due to the presence of more number of non-bridging oxygen in Sr substituted glasses than Ba substituted glasses. The Ba substituted samples were observed to be denser than Sr substituted glasses. Ultrasonic longitudinal and sheer velocities were found in the range of 3160–3210 and 1785–1850 m/s, respectively and were observed to be higher in Ba substituted glasses. The ac conductivity spectra were found to follow Jonscher power law and conduction mechanism is governed by overlapping large polaron tunneling model created with non-bridging oxygen and Tellurium ions.