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

Abstract

Eutectic fibers consisting of an ordered arrangement of LiF fibrils inside a LiREF 4 matrix (RE = Y, Gd) can be grown with the micro-pulling-down method at sufficiently large pulling rate exceeding 120 mm/h. The distance between individual fibrils could be scaled down to 1 µm at 300 mm/h pulling. LiF-LiYF 4 has stronger tendency to form facetted eutectic colonies than LiF-LiGdF 4 , explained by the larger entropy of melting of the former.

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

“…First, no segregation of erbium would be expected in Erbium doped LiYF 4 single crystals because the distribution coefficient of Er 3+ in LiYF 4 is very close to 1, based on previous works 32,33,34 . Secondly, although Thoma The microstructure of samples prepared by mPD at pulling rates from 15 to 300 mm/h was described by Klimm et al 24 . In Fig.…”

“…YF 3 was synthesized in this case from the oxide (Y 2 O 3 , AlfaAesar, 99.99 %) by a hydrofluorination method 28 under reactive atmosphere of HF and Ar. The absence of oxygen in the starting compounds was controlled by DTA measurements 24 . A platinum wire seed and an Ar atmosphere (1 bar, 99.999 % purity, <1 ppm water) were used to grow samples at pulling rates from 15 to 300 mm/h.…”