KNaSiF₆: a noncentrosymmetric deep ultraviolet optical crystal.

Authors

Zeyu Zhou, Wanxing Liu, Yuechen Gong, Dakun Zhou, Jinglin Feng, Ye Lei, Yongming Huang, Chao Yang, Qing Li, Zijin Wu, Changcheng Tang

Published in

Acta crystallographica Section B, Structural science, crystal engineering and materials. Oct 01, 2026. Epub Oct 01, 2026.

Abstract

Deep-ultraviolet (DUV) optical materials with wide bandgaps and non-centrosymmetric structures are critical for advanced optoelectronic applications such as DUV lithography, high-resolution spectroscopy and nonlinear optics. In this work, we report the discovery of a noncentrosymmetric phase of KNaSiF₆ (space group Pna2₁), synthesized via a hydrothermal cation-exchange method. Single crystals with dimensions up to 4.45 mm × 1 mm × 1 mm were grown. The crystal exhibits an absorption edge below 200 nm, corresponding to a bandgap greater than 6.2 eV. Vibrational spectroscopy (IR and Raman) confirms the integrity of the [SiF₆]^2- anionic groups, and energy-dispersive X-ray spectroscopy verifies the expected stoichiometry. First-principles calculations on the Pna2₁ phase yield a small second-harmonic generation (SHG) coefficient of ∼0.00227 pm V^-1, consistent with the weak SHG response observed experimentally. The combination of a DUV transparency window, a wide bandgap and a noncentrosymmetric structure renders Pna2₁-KNaSiF₆ a promising candidate for next-generation DUV optical windows and nonlinear optical crystals.

PMID:
42704726
Bibliographic data and abstract were imported from PubMed on 08 Sep 2026.

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