Polycrystalline (Y_0.7Gd_0.3)₂O ₃:Eu³⁺ ceramics fabricated by Spark Plasma Sintering: Densification and microstructure development

Using Spark Plasma Sintering it is possible to produce polycrystalline ceramics of very fine microstructure and good mechanical properties. This work presents the fabrication of such ceramics using Eu³⁺-doped (Y _0.7Gd_0.3)₂O₃ nanopowder as a starting material. We monitored the changes in the morphology of ceramic samples and their consolidation with additional thermal treatments at 650 °C and 1100 °C. The ceramics grain size remained in the sub-micron domain, even when elevated temperatures were used for annealing. The best results were obtained for the sample sintered at 1100 °C for 20 min, which had the smallest grain size, theoretical density, and the most intensive photoluminescence, along with the maximum hardness and appropriate fracture toughness. The Judd-Ofelt intensity parameters and branching ratios were calculated, taking into account the difference in the effective refractive index for the nanopowder and ceramic samples.