Effect of incorporation of alkali earth metal oxide on structural, optical and DC conduction mechanism in tellurium-phosphate glassy systems

The influence of alkali earth metal oxide on the structural, optical and electrical properties of inorganic glasses having chemical composition x CaO–(0.35- x ) BaO–0.40TeO 2 –0.25P 2 O 5 ( x = 0.0, 0.05, 0.1, 0.15, 0.20, 0.25, and 0.35) were studied and prepared by melt-quenching method. With an increase in CaO concentration ( x ), it was found that physical characteristics like density (4.5 to 3.9 g cm –3 ) and oxygen packing density (57.2 to 59.8 mol-litre –1 ) decreased and increased, respectively. The Rietveld refinement process was used to analyse the x = 0.0 and x = 0.25 samples, revealing peaks were primarily due to the hexagonal Ba 2 P 2 O 7 and tetragonal TeO 2 phases, respectively. The Te–O bond of the TeO 4 tetrahedral unit, Te–O–Te linkage, and PO 3 2– groups inside the glass matrix were among the several bond configurations that were identified using Raman spectroscopy. The value of the optical bandgap energy reduced with the inclusion of CaO up to sample x = 0.15, after which it was found to increase and Urbach energy, on the other hand, followed the opposite trend. The absorbance and reflectance spectra were studied and different optical parameters like absorption coefficient, extinction coefficient, reflectivity, refraction index, polarizability, etc., were studied and discussed. The determined values of third-order optical susceptibility and non-linear refractive index suggested potential optoelectronic applications because it was observed that they increased up to x = 0.15 sample before reducing once more. The DC conductivity value ranged from 5.85 to − 3.85 Ω –1 cm –1 in the log scale, and it was noticed that DC conductivity increased up to x = 0.15 before decrementing once more. The process of DC conductivity was described by Mott and Greaves’s variable range hopping model, and it was observed that DC conductivity increased as hopping distance and hopping energy values decreased. The highest conductivity was found in the sample with x = 0.15, while ternary composites exhibited conductivities that were lower than those of all other quaternary samples.