Room-temperature synthesis of χ-Al2O3 and ruby (α-Cr:Al2O3)

Abstract

In this work, we present a unique crystal growth synthesis of χ-Al₂O₃ accompanied with α-Cr:Al₂O₃ at room temperature. Raman spectroscopy and additions of Cr₂O₃ are key to identifying α-Cr:Al₂O₃ in trace amounts by the room temperature synthesis of ruby (α-Cr:Al₂O₃). The presence of this phase is further confirmed with HRTEM. The raw materials are pseudoboehmite and Cr₂O₃ that are treated mechano-chemically for the successful synthesis of ruby and χ-Al₂O₃. A thermal analysis approach is provided to explain the significant temperature reduction for the complete transformation to α-Cr:Al₂O₃ during annealing. The α-Cr:Al₂O₃ synthesized at room temperature acts as the seed or hetero site for nucleation and is responsible for a temperature drop of approximately 200 °C (up to 867 °C). This material is ideal for optics, photonics, defense, energy storage and harvesting, among other strategic applications.