Supercritical hydrothermal synthesis of polycrystalline gadolinium aluminum perovskite materials (GdAlO<sub>3</sub>, 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.