STUDY OF LiGd1-xLuxF4 SOLID SOLUTIONS AIMING THE CRYSTAL GROWTH

Author(s)

Ivanildo Antonio dos Santos

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Pesquisas Energéticas e Nucleares (IPEN/BT)
• Defense date: 2008-04-29

Examining board members

Izilda Marcia Ranieri; Sonia Licia Baldochi; Antonio Carlos Hernandes

• Advisor: Izilda Marcia Ranieri

Abstract

In this work the melting behavior of LiGd1-xLuxF4 solid solutions were studied utilizing the melting zone technique, aiming the development of new solid-state-laser matrices. Initially, crystals with composition of LiGd0.5Lu0.5F4 were systematically investigated using this method. The chemical and physical characterization of the ingots showed that this compound presents an incongruent melting behavior. Latter, some compositions of LiGd1-xLuxF4 (x = 0.60; 0.65 and 0.75) were studied to determine the composition where the LiGdF4-LiLuF4 pseudo-system starts with the formation of congruent compounds. The ingots characterization using scanning electron microscopy, energy dispersive spectrometry and X-ray diffraction, allowed to determine that the LiGd1-xLuxF4 compounds melt congruently from x values around 75 mol%. In this phase, all syntheses and zone melting processes were realized under a HF reactive atmosphere, to obtain high purity compounds. Two crystals with nominal compositions of LiGd0.25Lu0.75F4 and LiGd0.232Lu0.75Nd0.018F4 were grown from the melt by the Czochralski method, under an Ar+CF4 atmosphere. From ICP-OES concentration data, taking into account the Nd doped crystal, it was established that Lu and Gd concentrations are not constant along the crystal and there is a competition between Nd and Gd ions to be incorporated in the lattice. The calculated mean value for Nd segregation coefficient was 0.22(1), for Lu was 1.10(1) and for Gd was 0.61(1). The optical spectroscopy revealed that there is a broadening of the absorption bands in comparison with that of LiLuF4:Nd. The absorption cross sections and the 4F3/2 level lifetime were obtained for three samples with different Nd compositions. vii SUMÁRIO (AU)