Hydrothermal synthesis of perovskite and pyrochlore powders of potassium tantalate

Creators: Goh, Gregory K. L.; Haile, Sossina M.; Levi, Carlos G.; Lange, Fred F.

Abstract

Potassium tantalate powders were hydrothermally synthesized at 100 to 200 °C in 4 to 15 M aqueous KOH solutions. A defect pyrochlore, Kta_(2)O_(5)(OH). nH2O (n ≈ 1.4), was obtained at 4 M KOH, but at 7–12 M KOH, this pyrochlore was gradually replaced by a defect perovskite as the stable phase. At 15 M KOH, there was no intermediate pyrochlore, only a defect perovskite, K_(0.85)Ta_(0.92)O_(2.43)(OH)_(0.57) 0.15H_(2)O. Synthesis at higher KOH concentrations led to greater incorporation of protons in the perovskite structures. The potassium vacancies required for charge compensation of incorporated protons could accommodate water molecules in the perovskite structure.

Additional Information

© 2002 Materials Research Society. Received 16 May 2002; accepted 17 September 2002. Published online by Cambridge University Press: 31 January 2011. This work was supported by the Materials Research Laboratory program of the National Science Foundation under Award No. DMR00-80034. G.K.L. Goh acknowledges the Institute of Materials Research and Engineering (Singapore) for the provision of a research scholarship. Dr. Sonjong Hwang of the California Institute of Technology kindly collected the NMR data.

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