Influence of the atmosphere on the growth of LiYF₄ single crystal fibers by the micro‐pulling‐down method

Abstract

Micro‐pulling‐down growth of LiYF4 single crystal fibers have been performed under different gas atmospheres using stoichiometric LiYF4 single crystal pieces from prior Czochralski experiments as starting material. Completely transparent and phase pure LiYF4 single crystal fibers could be obtained after evacuation of the recipient to 2×10‐6 mbar and subsequent filling with pure (99.995%) CF4 gas. Using a gas mixture of 5% CF4 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 CF4 atmosphere reveal congruent melting behavior. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Directional solidification of the eutectic LiF–LiYF4 using Bridgman and micro-pulling down techniques: Microstructural study and some properties

“…Powders of 99.99 % purity (Alfa Aesar) were used and previously dried at 400 o C. The mechanically mixed powder was introduced -typically 14 g charge-in a graphite carbon crucible and was melted at the eutectic temperature of 702 o C 20 . As traces of oxygen or moisture certainly affects the growth of rare earth fluorides and its optical properties, extreme dry and oxygen free conditions are desirable 25 . A vacuum of 10 −2 mbar was reached in the chamber.…”

Out of the blue: semiconductor laser pumped visible rare‐earth doped lasers

“…However, the growth imposes difficulties. According to some authors, it does not grow from a perfectly stoichiometric melt and it requires even more reducing growth atmospheres, often containing HF , than other fluoride host materials. In contrast, the isostructural LiLuF 4 (LLF), featuring very similar spectroscopic and thermo‐mechanical properties, can be grown from a stoichiometric melt under less aggressive growth atmospheres .…”

Growth of Self Organized Eutectic Fibers from LiF─Rare Earth Fluoride Systems

“…Eutectic LiF/LiYF 4 and LiF/LiGdF 4 rods were grown in a µ-PD apparatus that was recently used for the growth of LiYF 4 single crystals [11]. The whole setup (Fig.…”