Preparation and properties of pressureless-sintered dense calcite ceramics

- Calcite powder was sintered to 99% density in air.
- Sintering aid in the LiF - NaF - KF eutectic mixture was used.
- Mechanical, thermal, and electrical properties were evaluated.

This paper describes a method for pressureless sintering of calcite (CaCO3) powders and the physical properties of the obtained dense calcite ceramics. Eutectic mixture of the KF - NaF - LiF system was found to be a good sintering aid that promoted the densification and the grain growth of calcite. Calcite sample with high relative density of 99.0% was attained on sintering the calcite fine powder at temperatures as low as 723 K for 3 h in air, without calcite undergoing thermal decomposition. Particle size of the calcite powder was found to be an important factor in achieving densification. The thermal conductivity and dielectric constant were found to be close to those of calcite single crystals; however, Vickers hardness and Young's modulus were lower than those of calcite single crystals. Thermally stimulated depolarization current of calcite ceramics was higher than that of calcite single crystals and hydroxyapatite ceramics.

425