Relationship between densification behavior and stabilization of quasi-liquid grain boundary layers in CuO-doped 0.7CaTiO3–0.3NdAlO3 microwave ceramics

In a combination with aberration-corrected TEM and water quench treatment, CuO–xCu2O grain boundary quasi-liquid layers in multicomponent 0.7CaTiO3–0.3NdAlO3 perovskite microwave ceramics doped by 0.5 wt% CuO are observed. Their structure and chemistry are identified. The relationship between their stabilization and densification behavior during the early sintering stage is clarified by constant-heating-rate/isothermal sintering experiments. It is revealed that the densification of CuO-doped 0.7CaTiO3–0.3NdAlO3 ceramics is dominated by viscous flow mechanism. Additionally, the appearance of quasi-liquid layers during the early sintering stage promotes mass transport by short-circuit diffusion. These results can be used as a guide to control the microstructure and properties of microwave ceramics.

Graphical abstractEnhanced densification mechanism of 0.5 wt% CuO doped 0.7CaTiO3–0.3NdAlO3 perovskite microwave ceramics is viscous flow (n ≈ 0) due to CuO–xCu2O eutectic oxides quasi-liquid layers on the grain boundary during the early stage of sintering.Figure optionsDownload full-size imageDownload high-quality image (207 K)Download as PowerPoint slide