Synthesis and characterization of translucent hafnia ceramics

This publication presents a comprehensive study on the synthesis and characterization of translucent hafnia ceramics with the emphasis on minimal intrinsic defects. Four different chemical synthesis methods: hydrothermal, solvothermal, microwave-assisted hydrothermal, and microwave-assisted solvothermal, were employed to obtain nanostructured hafnia ceramics. The microstructure and translucency of the ceramics were examined to highlight the significant role played by synthesis methods and sintering on the structure and composition of the samples. The hydrothermal method yielded ceramics with uniform grains and small, uniform pores, resulting in enhanced translucency. In contrast, the solvothermal method led to ceramics with coarser grains and an excess of sub-oxide species, leading to increased absorption of visible light. Sintering the ceramics effectively reduced porosity and further improved translucency. XPS analysis confirmed the presence of hafnium dioxide and sub-oxide species in the ceramics. The hydrothermal method ceramics exhibited a balanced distribution of oxide and sub-oxide, contributing to their lower opacity. Thermoluminescence measurements provided insights into the intrinsic defect parameters of the ceramics, with solvothermal samples displaying more prominent peaks associated with oxygen vacancies and sub-oxide presence. Doping with Eu³⁺ and Nb⁵⁺ proved effective in reducing defects, especially in the hydrothermal samples.