# X-ray Structure Refinements and Strain Analysis of Substituted Cubic Lead Pyrochlores $Pb_2(M_{2- y}Pb_y)O_{7-\delta}(0.0 < y< 0.8; M=Nb or Ta)$

Nalini, G and Somashekar, R and Row, Guru TN (2001) X-ray Structure Refinements and Strain Analysis of Substituted Cubic Lead Pyrochlores $Pb_2(M_{2- y}Pb_y)O_{7-\delta}(0.0 < y< 0.8; M=Nb or Ta)$. In: Journal of Solid State Chemistry, 156 (1). pp. 207-212.

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## Abstract

The phase diagrams in the $PbO-Nb_2O_5$ system and the $PbO-Ta_2O_5$ system depict pyrochlore structure at certain molar ratios. Compositions $Pb_2Nb_{1.51}Pb_{0.49}O_{6.30}$ (1), $Pb_2Ta_{1.4}Pb_{O.6}O_{6.21}$ (2), and $Pb_2Ta_{1.25}Pb_{0.75}O_{6.57}$ (3) belonging to this family, are refined in the cubic space group $Fd\bar{3}m$(Z=8; lattice parameter a=10.762(1), 10.744(1), 10.757(5) $\AA$, respectively) using the Rietveld refinement approach. The analyses suggest that the B-site is partially occupied by Pb leading to the general formula $Pb_2(M_{2-y}Pb_y)O_{7-\delta}(0.0<y<0.8; M=Nb\hspace{2mm}or\hspace{2mm}Ta)$. There is an overall broadening observed in the X-ray peak widths in 1, 2, and 3 compared to the Pb-deficient parent phases. It is observed that the X-ray peak widths of 2 is broad, while 3 displays narrow peak widths. It is found via strain analysis that the line broadening observed correlates with the strain in the lattice.

Item Type: Journal Article Copyright of this article belongs to Elsevier. Pyrochlore;Rietveld re5nement;strain analysis;Lead niobates;Lead tantalates Division of Chemical Sciences > Solid State & Structural Chemistry Unit 06 Jun 2006 19 Sep 2010 04:29 http://eprints.iisc.ernet.in/id/eprint/7528