Sintering, microstructural and mechanical characterization of combustion synthesized y₂O₃ and Yb³⁺-Y₂O ₃

The present work highlights the microstructural features and mechanical properties of Y₂O₃ prepared with and without Yb ³⁺ doping that processed through combustion synthesis involving various organic fuels such as urea, citric acid and glycine. Properties such as powder-flow, particle packing, green density, % of shrinkage, sintered density, grain size, Vicker's microhardness (H_v) and fracture toughness (K_IC) were analyzed and compared with respect to the fuel sources. The as combusted precursors were calcined at 1100°C for 4 h under oxygen atmosphere to obtain fully crystalline Y₂O₃ powders. Cylindrical pellets were fabricated as test specimens and sintered at 1600°C for 3 h. The SEM images of the sintered yttria samples show an average grain size of < 3 μm irrespective of the fuels. However, the mechanical properties show significant dependence on the fuels used. A maximum hardness of 6.8 ± 0.1 and 7.0 ± 0.1 GPa was obtained for Y₂O ₃ and Yb³⁺ doped Y₂O₃ derived from glycine fuel. Whereas the maximum fracture toughness of 2.6 ± 0.3 MPa m^1/2 was obtained for the samples derived from urea. The Yb ³⁺ doping found to increase the bulk hardness of yttria from 0.2 to 0.6 GPa. The study contributes to appropriately select the fuels for obtaining high dense, mechanically stable yttria ceramics through combustion process.