Synthesis of SrHfO3 Co-doped with Gd2O3 and Yb2O3 for thermal barrier coating applications

Abstract

In thermal barrier coatings (TBCs), ceramic material (YSZ) acts as a topcoat layer. Recently, perovskites (ABO3) materials are consider as a substitute for YSZ, which are used in gas turbines, aircrafts and jet engines etc. The SrHfO3 perovskite has high melting point but phase transformation occurs at 1130°C. Due to this phase transformation, its shows significant changes in its volume. To overcome this problem, SrHfO3 is co-doping with the rare earth oxide materials (Gd2O3 and Yb2O3). The main aim of this work is to co-dope 5 mol% Gd2O3 and 5 mol% Yb2O3 with SrHfO3 by using a mechanical solid-state method. The obtained mixture is annealed at 1450°C at a rate of increase of 3°C/min for 24 h. The phase and structural information are characterized by X-Ray Diffraction (XRD). The attained powder is sintered at 1700°C for 15 min with a spark plasma sintering (SPS), to form a pellet. The pellet density and the relative density is measured by using Archimede’s technique. Thermal gravimetric and differential thermal analysis (TG-DTA) are used to examine the phase purity. The morphology, and composition analysis are examined by using Field emission scanning electron microscopy (FESEM) followed by Energy dispersive spectroscopy (EDS) respectively. The refined powder is in an orthorhombic structure and observed by using XRD. The relative density of pellet is 95.1% and fractional porosity is 4.9%. TG-DTA graph shows no phase transformation and weight loss is <3%. Morphology of the grain boundaries and elemental analysis are observed by FESEM & EDS respectively.