Stabilization of high temperature hexagonal phase of SrAl2O4 at room temperature: role of ZnO

Abstract

Strontium aluminate (SrAl₂O₄) exhibits a monoclinic structure at room temperature (RT) and transforms to a hexagonal structure at above 650 °C, reported previously in the literature. In this article, we have shown a stable, high temperature hexagonal phase of SrAl₂O₄ (SAO) at RT by synthesizing a SAO–ZnO composite through a combustion technique. While SAO crystallizes in the monoclinic phase by adding 2.5 wt% of ZnO, a stable hexagonal phase of SAO at RT has been obtained for 20 wt% of ZnO. Further, the hexagonal phase of SAO transforms to a monoclinic phase after increasing the calcination temperature from 700 to 1200 °C. The role of ZnO in determining the structure and photoluminescence properties of these composites are discussed.