title: Structural analysis of lead magnesium niobate using synchrotron powder X-ray diffraction and the Rietveld method.
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 (Pm\bar 3m) and the local rhombohedral phase (R3m) corresponding to polar nanoregions (PNRs) are made using the Rietveld method. Rietveld refinements show that neither cubic (Pm\bar 3m) nor rhombohedral (R3m) 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.
authors.affiliation: Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, India.
authors.forename: Ashok
authors.initials: A
authors.lastname: Bhakar
authors.affiliation: Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, India.
authors.forename: Adityanarayan H
authors.initials: AH
authors.lastname: Pandey
authors.affiliation: Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, India.
authors.forename: M N
authors.initials: MN
authors.lastname: Singh
authors.affiliation: Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, India.
authors.forename: Anuj
authors.initials: A
authors.lastname: Upadhyay
authors.affiliation: Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, India.
authors.forename: A K
authors.initials: AK
authors.lastname: Sinha
authors.affiliation: Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, India.
authors.forename: S M
authors.initials: SM
authors.lastname: Gupta
authors.affiliation: Indus Synchrotrons Utilization Division, Raja Ramanna Centre for Advanced Technology, Indore 452013, India.
authors.forename: Tapas
authors.initials: T
authors.lastname: Ganguli
keywords: Rietveld method; lead magnesium niobate; polar nanoregions; powder diffraction; relaxor ceramic