[14a-F203-1~13] 15.1 Bulk crystal growth

[14a-F203-9] Partitioning of Al-Ga complex during melt growth of Ca₃Ta(Ga,Al)₃Si₂O₁₄

Shuhei Sakano¹, Chihiro Koyama¹, Junpei Okada¹, 〇Satoshi Uda¹ (1.IMR Tohoku Univ.)

Keywords:langasite-type crystal, Al doping, partitioning

An Al-doped CTGS crystal, which is one of the langasite-type crystal with A₃BC₃D₂O₁₄ structure, was grown via a µ-PD technique. The occupied crystal site by Al and the equilibrium partition coefficient, k₀, of Al were investigated. By applying the ‘degree of freedom in a site’ to each site of CTGS, it is turned out that Al is present only in C site by replacing Ga. Thus, the chemical formula is presented by Ca₃Ta(Ga_1-xAl_x)₃Si₂O₁₄. Chemical analysis via an EPMA demonstrated that k₀ of Al and as well as k₀ of Ga are unity for almost the entire range of x. A simple thermodynamic consideration allows us to propose that Al-Ga complex is present in the melt, which is partitioned into crystal with its 'k₀'=1 to become C site in the crystal.