R2: Crystal structure, crystal chemistry, physical properties of minerals, crystal growth and applied mineralogy

[R2-13] Crystal chemistry of loparite (Na, REE, Ca)(Ti, Nb)O₃: on the average and local structures

「発表賞エントリー」

*Ginga Kitahara¹, Akira Yoshiasa¹, Tsubasa Tobase², Makoto Tokuda³, Kazumasa Sugiyama³ (1. Kumamoto Univ., 2. HPSTAR, 3. Tohoku Univ.)

Keywords:loparite, XAFS, single crystal X-ray diffraction, local structure, average structure

Loparite has a perovskite-type structure ABX₃. To understand the detailed structure of loparite, we performed local structure analysis of trace elements by XAFS experiments and average structure analysis by single crystal X-ray diffraction.
We used loparite crystal: (Na_0.57, REE_0.31, Ca_0.07)(Ti_0.75, Nb_0.25)O₃ from Russia. We could refine the structure to R-3c and I4/mcm. On the other hands, it was shown that the local distortion of B-site from K-edge XANES of Ti and Nb is very large. Therefore in the view of local structure, the structure of loparite is more suitable to rhombohedral.