Crystallisation of ZnO from supercooled melts and glasses

The aim of this study is to achieve the crystallization of ZnO as a primary phase from multicomponent supercooled oxide melts and after additional heat treatment. Different compositions containing 70-80 mol% ZnO were selected. Transition metal oxides V2O5, WO3 and MoO 3 were added to decrease the melting temperature below 1400°C. In order to improve glass formation tendency up to 20 mol% B2O 3 and SiO2 were added. Bulk translucent greenish samples were obtained by quenching between two copper plates. Depending on the compositions they are x-ray amorphous or mixtures of glass and crystals. SEM observations indicate that microsized ZnO crystals with different morphologies were dispersed in an amorphous matrix. According to DTA data the glass transition temperature (Tg) is in the range 350-450°C and crystallization temperature (Tx) is near 650°C. It was suggested that ZnO takes part in the formation of the amorphous network by four-fold coordinated polyhedra. The synthesised products are potential candidates for the preparation of new functional materials.