Development and characterization of molybdenum-manganese phosphates glasses

Full text: It is well know that phosphate glasses are hygroscopic depending on the composition, and usually this drawback can be solved by adding alumina or transitions metals in the glass composition. In this work we have characterized phosphate glasses 40 P₂O₅ , x MoO₃ (10-x) MnO₂ - 50ZnO (mol%), melted in air and alumina crucibles. X ray diffraction pattern showed that glasses could be made without any crystallization phase. The molar volume had a linear increase from 32,5 to 34,5 cm³ /mol when MoO₃ varied from 0 to 10 mol%. Thermal differential (DTA/TG) results indicated that the glass transition temperatures is about 430 deg C and the crystallization peaks around 650 deg C.The refractive index did not present any chance as MoO₃ are added to the composition, being about 1.585 when measured at 546 nm. By means of spectrophotometry, it is shown that such glasses have a transmittance of about 80% above 450 nm, and their IR cutoff is about 4000 nm. EPR measurements showed that the spectroscopic splitting factor g = 1,928 due to Mo⁵⁺ suggesting that such ions are coordinated fivefold by oxygen atoms. As the MoO₃ concentration increases the hyperfine structure vanishes, and it is more prominent at low MnO₂ concentrations. The results suggest that Mo improves the glass formation avoiding it proneness to water, although their transmittance in the visible spectral region is affected. References: Ghauri, M. et al., J. Non-Cryst. Sol. 355 (2009)2466. (author)