Issue 48, 2017

Molten BaCN2 for the sintering and crystal growth of dielectric oxynitride perovskites Sr1−xBaxTaO2N (x = 0.04–0.23)

Abstract

Solid phase sintering of dielectric oxynitride perovskites above 1000 °C is accompanied by their decomposition. Post-ammonolysis is required to recover their stoichiometric nitrogen content and dielectric properties. In the present work, the oxynitride perovskite SrTaO2N was sintered with a BaCN2 flux at approximately 900 °C avoiding its thermal decomposition. The resulting solid product with a relative density of 68.9% showed relative dielectric constants in the range from 68 to 90 with loss values less than 0.11, without the post-ammonolysis. The interior of the solids contained rectangular Sr1−xBaxTaO2N crystals for which 0.04 ≤ x ≤ 0.23 reflecting their euhedral form. These crystals were grown in molten BaCN2 from 20 to 100 times larger than the original SrTaO2N particles and had a maximum grain size of 3.7 μm. The Sr1−xBaxTaO2N precipitated on the surfaces of the residual SrTaO2N crystals that had partially dissolved in the BaCN2 flux. A compositional gradient from barium-rich to strontium-rich was observed in a single crystal of the product on going from the exterior to the interior. This is the first-ever report of the preliminary liquid phase sintering and crystal growth of a dielectric oxynitride perovskite using a molten metal cyanamide.

Graphical abstract: Molten BaCN2 for the sintering and crystal growth of dielectric oxynitride perovskites Sr1−xBaxTaO2N (x = 0.04–0.23)

Supplementary files

Article information

Article type
Paper
Submitted
07 Oct 2017
Accepted
11 Nov 2017
First published
13 Nov 2017

Dalton Trans., 2017,46, 16837-16844

Molten BaCN2 for the sintering and crystal growth of dielectric oxynitride perovskites Sr1−xBaxTaO2N (x = 0.04–0.23)

A. Hosono, Y. Masubuchi, T. Endo and S. Kikkawa, Dalton Trans., 2017, 46, 16837 DOI: 10.1039/C7DT03765A

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