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Despite that the reported CaO-Ta2O5 phase diagram indicates its incongruent melting behavior, for the first time, we found that bulk single crystals of non-centrosymmetric CaTa4O11 can be grown successfully by the floating-zone method. The as-grown crystal rods (Ф 5-6 mm) have a black and colorless transparent appearance in Ar and O2 growth atmospheres, respectively. Consequently, the O2 atmosphere was selected to optimize its bulk crystal growth. The CaTa4O11 single crystals show a good crystallinity with a symmetric X-ray rocking curve for 004 diffraction with an FWHM of 72’’. For this new hexagonal bulk single crystal, its anisotropic optical, dielectric, and thermal properties were characterized. The crystal has a UV cut-off edge at 272 nm and a visible transmittance of ~75% till 800 nm . When excited by both 254 nm UV and X-ray, it shows a broad-band emission with a peak wavelength of around 427 nm. The dielectric constants ε11 and ε33 were found to be 30 and 52.3, respectively at 1 kHz. Meanwhile, the thermal conductivity along the c-axis is 5.69 Wm-1K-1, which is 1.8 times higher than that along the a-axis, which measures 3.19 Wm-1K-1 at room temperature.

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Keyword: Alkaline-earth tantalates; CaTa4O11; Crystal growth; Crystal characterization

Date published: 2024-10-14

Publisher: Royal Society of Chemistry

Journal:

• CRYSTENGCOMM (ISSN: 14668033) vol. 26 issue. 45

Funding:

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.5001

First published URL: https://doi.org/10.1039/D4CE00949E

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Updated at: 2025-10-21 16:17:03 +0900

Published on MDR: 2025-10-21 16:15:02 +0900