Search for content and authors
 

Chemical segregation in micro-pulling-down process: analytical model and experiments

Abdeldjalil Nehari 1,  Thierry Duffar 2,  Kheirreddine Lebbou 1

1. Institut Matière et Lumière Université Lyon (CNRS), Villeurbanne cedex 69622, France
2. SIMaP EPM, CNRS UJF, BP 75, Saint Martin d'Heres cedex 38402, France

Abstract
The micro-pulling down (µ-PD) process consists in pulling a crystal under a capillary channel placed at the bottom of a crucible. In spite of the fact that it is limited to rather small liquid volumes, it is used to grow single crystal fibers  and shaped crystals of various cross sections, mainly applied industrially for optical applications such as lasers, optics or scintillators. Consequently those crystals should be doped with active elements in order to fit the target application. Unfortunately, whatever the growth parameters and the dopant type, quite often segregation problem is observed.  It is generally believed that chemical segregations in µ-PD technique are restricted to the first grown millimeters, but some experiments show that it is not always the case.

An analytical one dimensional model is presented, aiming to predict the longitudinal segregation along the growth direction. It is shown that it depends in practice on growth parameters such as capillary length, meniscus height, crucible volume and growth rate. The characteristic numbers controlling the type of segregation that will be obtained are derived and a parametric study is performed in the case of Ti-doped sapphire single crystal fibers.

Such Ti:Al2O3 single crystal fibers oriented along c-axis have been grown under stationary stable regime using different pulling rates and the longitudinal chemical segregation has been characterized by photoluminescence. Results are in agreement with the model predictions.

 

Legal notice
  • Legal notice:

    Copyright (c) Pielaszek Research, all rights reserved.
    The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
    In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/29553 must be provided.

 

Related papers
  1. Dewetting as a powerful tool for thermoelectricity device applications
  2. Comparison of various methods for large scale dislocation density characterization
  3. Experimental study of the grain boundary orientations in multi-crystalline silicon
  4. Study of the zig-zag grain boundary in multicrystalline silicon
  5. Comparison of LGSO:Ce scintillator crystals grown by micro-PD and Czochralski methods
  6. Segregation study of titanium ions in sapphire single crystal fibers grown by the µ-PD technique

Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, General Session 2, by Thierry Duffar
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-04-12 18:49
Revised:   2013-07-23 16:50