Speaker
Description
Introduction
Titanium-based perovskite-type oxide ceramics for variable resistors [1] are conventionally produced by sintering green compacts in reducing atmospheres at ~1400 °C. We report the use of Na or K metal vapor to obtain conductive ceramics of CaTiO3, SrTiO3, and BaTiO3 below 1000 °C.
Experimental
Powder compacts of CaTiO3, SrTiO3, and BaTiO3 were placed into a boron nitride crucible and enclosed in a stainless-steel (SUS) container with Na or K metal in an Ar atmosphere. The containers were heated at 600–1000 °C for 1–10 h. Relative densities (RDs) and microstructures of the samples were evaluated by the Archimedes’ method and scanning electron microscopy.
Results and Discussion
BaTiO3 densified at the lowest temperature (~750 °C); maximum RDs (>96%) were achieved at 800–1000 °C for 2 h and the ceramics were conductive (~300 Ω cm) due to the reductivity of Na. Conductive ceramics of other perovskites were also obtained at 900 °C for 10 h. Cuboid grains in the ceramics suggests that a dissolution–precipitation process mediated by condensed Na vapor facilitates low-temperature densification. Furthermore, conductive BaTiO3 ceramics were obtained in the same temperature range with K vapor.
Acknowledgement
Supported by the Izumi Science and Technology Foundation as well as the Murata Science and Education Foundation.
Reference
[1]Heywang, J. Am. Ceram. Soc., 1964, 47, 484.
| Professional Status of the Speaker | Senior Scientist |
|---|---|
| Invitation letter for visa | No |
| Interest in submitting a paper in a special issue of | Journal of the European Ceramic Society (Elsevier) |
