Low-temperature sintering behaviors in a titanium oxide–copper oxide system through two-step heat treatment

The low-temperature sinterability of TiO2–CuO systems was examined through a two-step sintering process. The first-step heat treatment was carried out at 900 °C for either 5 min or 1 h. The subsequent second-step sintering by reheating after cooling proceeded at 800 °C for various times. Micron-sized (2 µm) powders as received were used as the starting materials. In the present system, the densification behaviors through grain-boundary diffusion were similar to those in nanocrystalline ceramics at low temperatures. The difference in temperature sensitivity for densification or grain growth was thus exploited to enhance densification and hinder grain growth. As a result, enhanced densification without notable grain growth was achieved after second-step sintering, as opposed to conventional sintering at 800 °C. This implies that the grain-boundary diffusion contributing to densification was more active than the grain-boundary migration at 800 °C. In this regard, the current results show a trait of activated sintering as well.