Atomically resolved precipitates/matrix interfaces in KTaO₃ crystals

Abstract

KTaO₃ is an incipient ferroelectric with its properties influenced by defects and the purity. In this paper, we investigated the microstructures of KTaO₃ by X-ray diffraction (XRD) and Cs-corrected scanning transmission electron microscopy (STEM). XRD and electron diffraction indicate that a second phase of K₆Ta_10.8O₃₀ precipitates from the matrix. Four orientation relationships were identified: (100)_m // ( 0)_p, [001]_m // [0 0 1]_p; (1 0 0)_m // ( 0)_p, [001]_m // [0 0 1]_p; (1 0 0)_m // (0 0 1)_p, [0 0 1]_m // [3 1 0]_p and (100)_m // ( 3 0)_p, [0 0 1]_m // [3 1 0]_p. High resolution imaging shows that the interfaces between the second phase and KaTaO₃ are distinct and coherent. Atomically resolved analysis identified two kinds of novel ordered defects at the interfaces with the termination planes either KO plane of KTaO₃ or TaO₂ plane of KTaO₃.

Keywords:

• High resolution (scanning) transmission electron microscopy
• precipitate
• interface structures
• orientation relationships
• KTaO₃

Acknowledgements

The authors are grateful to Dr X.B. Hu for fruitful discussions, Mr. B. Wu and Mr. L.X. Yang of this laboratory for their technical support on the Titan platform of the Titan^{3 TM} G2 60–300 kV aberration-corrected scanning transmission electron microscope.