Growth of K5Li2NdF10 and K5Li2PrF10 crystals by the Bridgman method

Piotr Solarz 

Polish Academy of Sciences, Institute of Low Temperature and Structure Research (INTiBS), Okólna 2, Wrocław 50-422, Poland

Abstract
The growth of congruently melting K5Li2NdF10 and K5Li2PrF10 (KLLF) crystals by the Bridgman method is reported. The structure of these crystals are orthorhombic, with the space group Pnma. The unit-cell parameters are a = 2.0775 nm, b = 0.7822 nm and c = 0.6963 for the K5Li2LaF10 crystal and they change a little upon submissions of other lanthanide in the series from La to Gd [1]. The crystal structure is built from layers perpendicular to the a axis, formed by LnF8 dodecahedra and LiF4 tetrahedra. Lanthanide and lithium ions occupy sites with point symmetry Cs whereas potassium and fluorine ions occupy sites with Cs and C1 symmetry. The polyhedra do not share fluorine ions and the closest lanthanide ion are separated by about 0.65 nm. Owning these features, exchange interactions between Ln ions maybe neglected. Based on the crystallographic structure, there is only one site for the lanthanide ions.

A stoichiometric mixture of appropriate LiF, KF, NdF3 and PrF3 was preliminary heated at about 500 K for 2 hours at vacuum conditions to remove traces of water. Then it was heated up to 1100 K for at least 2.5 hours, under Ar atmosphere, to accomplish the reaction. Finally the single crystal of KLLF were grown by the Bridgman one-zone method in the following conditions: the melt temperature 900 K, temperature gradient 120 K/cm, pulling rate 1 mm/h. For crystal growth the IG-110 graphite were used which gives also the possibility to remove traces of oxygen.

[1] P. Solarz and W. Ryba-Romanowski, Phys. Rev. B 72 (2005) 075105

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Presentation: Poster at Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth, by Piotr Solarz
See On-line Journal of Joint Fith International Conference on Solid State Crystals & Eighth Polish Conference on Crystal Growth

Submitted: 2007-01-16 11:10
Revised:   2007-05-09 22:23
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