Influence of the atmosphere on the growth of LiYF 4 single crystal fibers by the micro‐pulling‐down method

Micro‐pulling‐down growth of LiYF 4 single crystal fibers have been performed under different gas atmospheres using stoichiometric LiYF 4 single crystal pieces from prior Czochralski experiments as starting material. Completely transparent and phase pure LiYF 4 single crystal fibers could be obtained after evacuation of the recipient to 2×10 ‐6 mbar and subsequent filling with pure (99.995%) CF 4 gas. Using a gas mixture of 5% CF 4 in Argon or pure 5N Argon leads to the formation of micro crystallites of oxofluorides on the surface. Evacuating only to 3 × 10 ‐3 mbar leads, independently of atmosphere, to completely white fibers that are heavily contaminated with oxofluorides. DSC measurements of the completely transparent fiber grown under pure CF 4 atmosphere reveal congruent melting behavior. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)