Supercritical hydrothermal synthesis of polycrystalline gadolinium aluminum perovskite materials (GdAlO3, GAP)

Abstract

The orthorhombic perovskite, Gadolinium aluminum oxide (GdAlO3, GAP) material was successfully prepared by hydrothermal supercritical fluid method using co-precipitated gel of GAP. All experiments were carried out in the pressure and temperature ranges of 100-150 MPa and 180-650 °C respectively. The as-prepared GAP samples were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray spectroscopy (EDS), thermo gravimetry (TGA) and differential thermo gravimetry analysis (DTA). The XRD profile confirms fully crystalline and orthorhombic nature of as-prepared materials, which is well correlated to the reported results. The SEM studies reveal that the GAP materials synthesized at 650 °C/150 MPa for 92 hrs possesses polycrystalline nature with average particle size in the range of 5-20 μm. The DTA shows a crystallization peak at 361 °C at this temperature the agglomerated GAP gel starts to crystallize into polycrystalline GAP materials. When compared with other methods, like sol-gel and solid-state reactions our crystallization temperature is very much lower and feasible. This work not only demonstrates a simple way to fabricate GAP polycrystalline materials from co-precipitated gels but also shows a possible utilization of same technique for synthesis of other high temperature materials.