Vegard's Rule Revisited in BaxPb1−x(NO3)2 by NMR and XRD

✍ Scribed by Guy A. Crundwell; Brett A. Cowans; Jeffrey A. Hopkins; John B. Grutzner; Bart Kahr

• Book ID: 102609064
• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 280 KB
• Volume: 145
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1999.8288

✦ Synopsis

Vegard:s rule, originally based on powder X-ray di4raction data from Ba x Pb 1؊x (NO 3 ) 2 , is reevaluated through the application of nuclear magnetic resonance (NMR) spectroscopy. Solid state 207 Pb NMR and 15 N NMR spectra of Ba x Pb 1؊x (NO 3 ) 2 (0.93 > x > 0.08) were recorded. The chemical shift dispersions for each magnetic nucleus are remarkable for their sensitivity to the nearest neighbor Pb 2؉ and Ba 2؉ distributions. The intensities of the peaks in the 207 Pb spectra and their deviations from a simple binomial dependence reveal a non-statistical incorporation of Ba 2؉ and Pb 2؉ in the bulk crystals. Complementary analyses were performed by powder X-ray di4raction and with electron spectroscopy for chemical analysis that reveal bulk heterogeneities varying with crystal growth conditions. Vegard:s original determination of a linear correlation between lattice constants and composition in Ba x Pb 1؊x (NO 3 ) 2 is shown to have been a favorable consequence of the low resolution X-ray 5lm methods available in the 1920s, but his additivity relationship is restored locally in the linear correlation of chemical shift with composition of the 5rst metal coordination sphere.