Dense and single-phase KTaO$_{3}$ ceramics obtained by spark plasma sintering

TL;DR

This study demonstrates that spark plasma sintering enables the production of dense, single-phase KTaO$_{3}$ ceramics with enhanced dielectric properties by optimizing composition and processing parameters.

Contribution

The paper introduces a novel sintering approach using spark plasma sintering to obtain high-quality KTaO$_{3}$ ceramics with controlled phase purity and improved dielectric performance.

Findings

2 mol% K-excess promotes large grain growth and single-phase ceramics.

Secondary phases can be removed by polishing.

Dielectric permittivity is four times higher with K-excess ceramics.

Abstract

Potassium tantalate (KTaO$_{3}$) is a promising material for dielectric applications at low temperature. However, dense and single-phase ceramics cannot be obtained by conventional sintering because of the evaporation of potassium that leads to secondary phases. Here, we demonstrate that spark plasma sintering is a suitable method to obtain dense and single-phase KTaO$_{3}$ ceramics, by optimizing three parameters: initial composition, temperature, and pressure. A 2 mol% K-excess in the precursors leads to a large grain growth and dense single-phase ceramics. Without K-excess, a small amount of secondary phase (K$_{6}$Ta$_{10.8}$O$_{30}$) is observed at the surface but can be removed by polishing. At 10 K, the dielectric permittivity is 4 times higher in the ceramic from the 2 mol% K-excess powder, because of the larger grain size. The thermal conductivity decreases with decreasing grain size and stays above the thermal conductivity of KNbO$_{3}$ ceramics.