Braunite phase embedded Y2O3/MnO2-Al2O3-CaO-SiO2 glass ceramics and their properties

Abstract Glass series ( 20-x )Y 2 O 3 - x MnO 2 -20Al 2 O 3 -40SiO 2 -20CaO ( x  = 5, 10, 15 and 20, mol%) have been synthesized by melt quench technique followed by sintering at 850 °C. The optical band gap of the samples is in wide semiconductor range and increased with MnO 2 content. Photoluminescence study exhibits emission in Mn 2+ d-states. On the other hand, hardness decreases with MnO 2 content except for 10 mol% MnO 2 containing glasses (YM10). The formation of braunite phase in glass ceramics induces capacitive losses. In lower temperature region, the conductivity behaviour of samples follows superlinear power law. In higher temperature region, it follows the universal law of conduction. The dielectric constant for the sintered glasses is constant with respect to temperature, approximately upto 350 °C and 1 MHz frequency. Above 350 °C, the ionic conduction dominates in all the sintered glasses. The anomaly in properties is observed when the ratio of Y 2 O 3 /MnO 2 is 1:1.