Lead-207 NMR Spectroscopic Study of Lead-Based Electronic Materials and Related Lead Oxides

Abstract

Static and MAS 207 Pb NMR spectra of a series of lead oxides, including the electronic materials PbTiO 3 (PT), PbZrO 3, Pb(Zr 0.53 Ti 0.47 )O 3, Pb(Mg 0.33 Nb 0.67 )O 3 (PMN), and 0.66PMN/0.34PT, have been measured. The chemical shift parameters (δ iso, δ aniso, and η) and the spin−lattice relaxation times have been determined for most of these compounds. The symmetry of the local environment of the lead(II) site and the covalency of the Pb−O bonds are determined to be the best indicators of the 207 Pb chemical shift parameters. Ionic compounds (e.g., PbSO 4 and Pb(NO 3 ) 2 ) have isotropic chemical shifts from −3600 to −2500 ppm and small absolute anisotropic chemical shifts (<500 ppm); while covalent lead oxides (e.g., PbO and Pb 3 O 4 ) have isotropic chemical shifts from 800 to 1900 ppm and large absolute anisotropic chemical shifts (1900 to 2600 ppm). PbTiO 3 and PbZrO 3 have intermediate isotropic (−1419 to −1017 ppm) and anisotropic chemical shifts (−838 to −546 ppm) consistent with an intermediate degree of covalent bonding. Pb(Zr 0.53 Ti 0.47 )O 3, PMN, and 0.66PMN/0.34PT have single broad asymmetric 207 Pb NMR resonances, with chemical shifts and line widths consistent with Pb−O bonds that are less covalent than those in PbO and more covalent than those in PbTiO 3 and PbZrO 3 . For the 207 Pb NMR spectra of Pb(Zr 0.53 Ti 0.47 )O 3, PMN, and 0.66PMN/0.34PT, chemical shift dispersion is a significant contribution to the line width, consistent with the presence of a range of inequivalent lead(II) sites in these disordered perovskite materials.