Structural analysis of lead magnesium niobate using synchrotron powder X‐ray diffraction and the Rietveld method. Issue 3 (1st June 2016)

• Record Type: Journal Article
• Authors: Bhakar, Ashok; Pandey, Adityanarayan H.; Singh, M. N.; Upadhyay, Anuj; Sinha, A. K.; Gupta, S. M.; Ganguli, Tapas
• Is Part Of: Acta crystallographica. Volume 72:Issue 3(2016:Jun.)
• Page Start: 404
• Page End: 409
• Publication Date: 2016-06-01
• Subjects: lead magnesium niobate -- powder diffraction -- Rietveld method -- polar nanoregions -- relaxor ceramic
• DOI: 10.1107/S2052520616006508
• Languages: English
• ISSNs: 2052-5206

Abstract

Abstract : The contribution of the polar rhombohedral phase ( R 3 m ) in a lead magnesium niobate (PMN) sample is determined using synchrotron XRD data at room temperature. The unit‐cell volume of this polar phase is a little larger than that of the paraelectric cubic phase in PMN. Abstract : The room‐temperature synchrotron powder X‐ray diffraction pattern of the single phase perovskite lead magnesium niobate (PMN) has shown significant broadening in the q range ∼ 5–7 Å −1 compared with standard LaB6 synchrotron powder X‐ray diffraction data, taken under similar conditions. This broadening/asymmetry lies mainly towards the lower 2θ side of the Bragg peaks. Attempts to fit this data with the paraelectric cubic phase ( ) and the local rhombohedral phase ( R 3 m ) corresponding to polar nanoregions (PNRs) are made using the Rietveld method. Rietveld refinements show that neither cubic ( ) nor rhombohedral ( R 3 m ) symmetry can fit this XRD pattern satisfactorily. The two‐phase refinement fits the experimental data satisfactorily and suggests that the weight percentage of the PNRs is approximately 12–16% at room temperature. The unit‐cell volume of these rhombohedral PNRs is approximately 0.15% larger than that of the unit cell volume of the paraelectric cubic phase.