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Crystal structures of (Ba1−xLax)[Mg(1+x)/3Nb(2−x)/3]O3 with 0.9 ≤ x ≤ 1.0

Published online by Cambridge University Press:  06 January 2012

Hyun Min Park
Affiliation:
New Materials Evaluation Center, Korea Research Institute of Standards and Science, Taeduk Science Town, P.O. Box 102, Taejon, 305–600, Korea
Hwack Joo Lee
Affiliation:
New Materials Evaluation Center, Korea Research Institute of Standards and Science, Taeduk Science Town, P.O. Box 102, Taejon, 305–600, Korea
Yang Koo Cho
Affiliation:
New Materials Evaluation Center, Korea Research Institute of Standards and Science, Taeduk Science Town, P.O. Box 102, Taejon, 305–600, Korea
Sahn Nahm
Affiliation:
Division of Materials and Metallurgical Engineering, Korea University, Seoul, 136–701, Korea
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Abstract

Based on a structure model of mixture of phases, the crystal structure analysis of (Ba1−xLax)[Mg(1+x)/3Nb(2−x)/3]O3 (BLMN) (x = 0.9 and 1.0) by Rietveld refinements was carried out. The pure La(Mg2/3Nb1/3)O3 (LMN) and BLMN (x=0.9) actually consist of a two-phase mixture rather a single phase. One is Fm-3m, which is cubic and 1:1 ordered and the other is P21/n, which is monoclinic and has both 1:1 ordering and the antiphase and inphase tilting of oxygen octahedra with aac+. The weight fraction of the Fm-3m phase is 17.5% at x=0.9 and further decreases to 7.5% in pure LMN. Meanwhile, that of the P21/n phase is 82.5% at x =0.9 and further increases to 92.5% in pure LMN. The I4/m phase, which is present as a minor phase from x=0.3 to 0.7, disappeared when x≥0.9. The abrupt change of the x-ray diffraction pattern at x=0.9 is caused by a change of major phase from Fm-3m to P21/n phase in the matrix.

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Articles
Copyright
Copyright © Materials Research Society 2003

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