Densification and Grain Growth for Powder-Derived Ta2O5-TiO2 Ceramics
Journal of the Ceramic Society of Japan
Thermal processing of powder-derived Ta 2 O 5 -based ceramics reveals that rapid grain growth associated with a high temperature phase transformation hinders densification, necessitating the development of a reducedtemperature processing methodology. Data are reported for the densification behavior with emphasis on microstructural changes associated with the phase transformation between a stable low-temperature phase L-Ta 2 O 5 and a phase which is stable at high temperatures H-Ta 2 O 5 . The
... H-Ta 2 O 5 . The H-Ta 2 O 5 phase is metastable at room temperature and reverts back to the L-Ta 2 O 5 phase with thermal or mechanical treatment. TiO 2 additions stabilize the H-Ta 2 O 5 phase and result in enhanced dielectric properties. Because TiO 2 additions decrease the temperature of the densification-hindering phase transformation, an alternate reduced-temperature processing route is necessary. A simple solution-coated powder method was used to produce the first-ever dense and chemically homogeneous TiO 2 -modified Ta 2 O 5 ceramics in both the L-and H-Ta 2 O 5 forms. Thus, this work represents the first comprehensive study of the effects of composition and the LsH-Ta 2 O 5 phase transformation on microstructural development. The results indicate that the effect of TiO 2 additions on the sintering behavior of Ta 2 O 5 ceramics was largely limited to a reduction in the temperature for the densification-hindering phase transformation.