Synthesis, Sintering, and Microwave Dielectric Properties of KTaO₃ Ceramics

Abstract

Studies of a synthesis of KTaO3 displayed a two‐step reaction path with the intermediate formation of K2Ta4O11. Thermal and X‐ray diffraction analysis showed that the synthesis is completed at 900°C. Sintering studies showed that KTaO3 powder can produce single phase ceramics with 85% of relative density with the addition of 5% of potassium excess when sintered at 1330°C for 1 h. Longer sintering times or higher temperatures result in enhanced potassium loss and consequent formation of K6Ta10.8O30 secondary phase with tetragonal tungsten bronze structure. Room‐ and low‐temperature microwave dielectric properties of KTaO3 ceramics compare well with measurements performed on single crystals. We evaluated the influence of microstructural features (porosity, structural defects, secondary phases) on the dielectric properties of the ceramic samples.

Influence of point defects in KTaO3 on low-temperature dielectric relaxation

“…The slope of the ε r (T) plot of pure KTaO 3 reflects the soft-mode driven increase of permittivity that follows Curie Weiss law. 4 At 20 K, the slope of permittivity is −2.4%/K. When substituting with 10%Na the slope does not change significantly reaching a value of −2.1%/K whereas a tenth of that amount of Mn substitution reduces the slope to −1.2%/K.…”

“…Sintering of KTaO 3 powder is very difficult mainly due to the high covalent bonding within this crystal structure. 4,5 More effective sintering has been obtained with an aid of dopants. 6,7 However, the dopants can significantly change functional properties (e.g.…”

Synthesis of K6Ta10.8O30 nanowires by molten salt technique

“…K 6 Ta 10.8 O 30 (KT) crystalline is of tetragonal tungsten bronze structure with lattice parameters a = 12.56, c = 3.978Å [24]. K 6 Ta 10.8 O 30 always appears as a secondary phase in the synthesis of KTaO 3 ceramics [25]. To the best of our knowledge, there are few reports on the fabrication of KT nanostructures, especially for single phase KT nanostructures [24].…”

KTaO3 Ceramics Prepared by the Mechanochemically Activated Solid-State Synthesis

“…The majority of the research activities on KTaO 3 has been focused on single crystals 4–6 . The reports on processing and dielectric properties of the ceramics are still very rare, 7–9 which is most probably related to difficulties encountered during processing, such as the hygroscopic nature of the starting compounds and losses of potassium oxide upon heating. Besides these problems, common for all alkaline‐based lead‐free ceramics, the covalent nature of the Ta–O bond 10 additionally contributes to the inhibition of the sintering process.…”