2. Experimental
Glass samples with the formula 20CaO–30ZnO–(x)B2O3–(50x)P2O5 with x varies in the range 0 6 x 6 50 mol% and 20CaO–30ZnO–20B2O3–30P2O5–(x)Mn2+ with x varies in the range 0 6 x 6 10 mol% were prepared by melt quenching technique. Required quantities of CaO, ZnO, B2O3, H3PO4 (85% liquid) were weighed separately in an electronic balance before being mixed thoroughly. The mixtures were calcined at 200 C for 30 min and 400 C for another 30 min to remove vapor and then were melted in a porcelain crucible at 1100 C for 15 min in an electric furnace during which the molten glass samples were taken out at certain intervals and stirred to ensure homogeneity. The homogenized melt was poured onto a preheated mould plate to avoid breaking of the sample due to thermal stress and pressed with another
plate to get the square-shaped sample. In order to prevent breaks and cracks, these glass samples were immediately annealed at 300 C for 3 h and then cooled slowly to room temperature.
the square-shaped sample