Structural investigations of neodymium incorporation in calcium stannate perovskite CaSnO3
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Samples of calcium stannate perovskite (CaSnO3) doped with a variable Nd content were synthesized by solid-state reaction in the system (1 − x)CaSnO3 − xNd2O3. The synthesized compounds were characterized by means of electron microprobe, powder X-ray diffraction, single-crystal X-ray diffraction and µ-Raman spectroscopy. The incorporation of Nd in the CaSnO3 Pbnm structure leads to the formation of a complex (Ca1 − 2x Nd2x)(Sn1 − xCax)O3 perovskite. The A sublattice contains a random distribution of Ca and Nd in the whole range of composition of this system. For x < 0.28, the structure is Pbnm with Ca and Sn randomly distributed in the B sublattice. For x > 0.28 a symmetry change occurs; the structure turns into rock salt type P21/n. In this latter case half of the octahedral sites are fully occupied by Sn and the other half is randomly occupied by Sn and Ca. For x = 0.28, both structures are present in the sample. The presence of a Raman two modes behavior of A1g symmetry located near 700 cm− 1 coupled with the continuous linear evolution of the lattice parameters with Nd incorporation supports the proposed substitution mechanism.
KeywordsPerovskite Calcium stannate Neodymium Raman spectroscopy X-ray diffraction
The authors are thankful to M. Fialin (Centre de Microanalyses Camparis, Université Pierre et Marie Curie, Paris VI) for his help with the electron microprobe, J-D Mertz (LRMH) and M. Duc (IFSTTAR) for their help with DRX, O. Majérus (IRCP) for her help with Raman Spectroscopy; and B. Mihailova, G. Wallez, F. Guyot for their stimulating discussions.
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