Effects of lanthanum addition on the structure and properties of iron phosphate glasses

The structural properties of xLa2O3–(100 − x)(0.4Fe2O3−0.6P2O5) (x = 0, 1, 2, 3, 4, 6, 8 mol%) glasses have been investigated by XRD, DTA, IR and Raman spectroscopy. XRD analysis has confirmed that the majority of samples are X-ray amorphous, and crystallization occurs when the glass containing 6 mol% La2O3, the crystalline phase is LaPO4. The IR spectra show that the glass structure does not produce any fundamental change with addition of La2O3 in the glass formation range, which consists predominantly of pyrophosphate, Q1 units. However, Raman spectra indicate that depolymerization of the phosphate network with the addition of La2O3 content. The glass transition temperature (Tg) increased with increasing La2O3 content for the glasses, which indicates that the addition of La2O3 increases the thermal stability of glasses in this series.