Sintering of high-density BaHf1–xScxO3–δ ceramics for proton-conducting electrochemical cells

Proton-conducting ceramics with high density exhibit superior mechanical and functional properties, which is crucial for electrochemical applications. However, most proton-conducting oxides, especially BaHfO3-based perovskites, have poor sinterability due to their highly refractory nature. Thus, the objective of this study is to develop a method for producing high-density BaHf1–xScxO3–δ ceramics. Various approaches were investigated, including the addition of a sintering aid, conventional sintering, two-step sintering, and the use of mixtures of coarse and fine powders. The analysis of the density and microstructure of the sintered ceramics revealed the most effective method for producing dense BaHf1–xScxO3–δ ceramics. Unlike conventional high-temperature sintering, this method involves isostatic pressing of the samples, the introduction of a sintering additive (ZnO), and a two-step sintering process. The ceramics obtained through this method exhibit a density that approaches 99 % of X-ray density.