Network former mixing effects in heavy metal oxide glasses: structural characterization of lead zinc phosphotellurite glasses using NMR and EPR spectroscopies.
OLIVEIRA JR., Marcos de; AMJAD, Raja Junaid; DE CAMARGO, Andrea Simone Stucchi; ECKERT, Hellmut.
OLIVEIRA JR., Marcos de; AMJAD, Raja Junaid; DE CAMARGO, Andrea Simone Stucchi; ECKERT, Hellmut.
 Abstract: Network former mixing effects in Yb3+-doped glasses in the system [(2TeO2)x(P2O5)1-x]0.6[(PbO)0.5- (ZnO)0.5]0.4 have been investigated using a comprehensive strategy involving complementary NMR (31P,125Te, 207Pb) and EPR (of Yb3+ probe ions) spectroscopies. Phosphate local environments and connectivities are extracted from detailed 31P MAS NMR line shape analyses with assignments to distinct Pn mTe sites supported by recoupling of homonuclear spin-spin interactions (refocused-INADEQUATE experiments). These results suggest a preference for P-O-Te over P-O-P and Te-O-Te connectivities for x < 0.5, consistent with nonlinear compositional trends of glass transition temperatures. While sharing of the network modifiers PbO and ZnO between the phosphate and the tellurite networks is close to proportional, the NMR data indicate subtle deviations favoring phosphate ligation at x > 0.6, where the anionic fraction of phosphate exceeds the expected fraction (67%) based on composition. On a local scale, nonlinear trends in 207Pb chemical shift parameters suggest the preferred formation of a ligand environment with approximately equal numbers of phosphate and tellurite ligands near x = 0.5, which persists over a wide composition range. While electron spin echo envelope modulation (ESEEM) experiments suggest that the overall elemental distribution appears to be homogeneous on a 1 nm distance scale, the EPR lineshapes suggest significant changes (and possibly inhomogeneous distributions) of the local Yb3+ environments. | |
| Journal of Physical Chemistry C |
| v. 122, n. 41, p. 23698-23711 - Ano: 2018 |
| Fator de Impacto: 4,484 |
| http://dx.doi.org/10.1021/acs.jpcc.8b07827 |  @article={002908370,author = {OLIVEIRA JR., Marcos de; AMJAD, Raja Junaid; DE CAMARGO, Andrea Simone Stucchi; ECKERT, Hellmut.},title={Network former mixing effects in heavy metal oxide glasses: structural characterization of lead zinc phosphotellurite glasses using NMR and EPR spectroscopies},journal={Journal of Physical Chemistry C},note={v. 122, n. 41, p. 23698-23711},year={2018}} |
