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@ARTICLE{Alderman:473934,
author = {Alderman, Oliver and Hannon, Alex and Holland, Diane and
Dupree, Ray and Feller, Steve},
title = {{S}tructural origin of the weak germanate anomaly in lead
germanate glass properties},
journal = {Journal of the American Ceramic Society},
volume = {105},
number = {2},
issn = {0002-7820},
address = {Westerville, Ohio},
publisher = {Soc.},
reportid = {PUBDB-2022-00352},
pages = {1010 - 1030},
year = {2022},
abstract = {Binary PbO–GeO$_2$ glasses have been studied in detail
from 5 to 75 mol\% PbO using high-resolution neutron
diffraction, high-energy X-ray diffraction, 207-Pb NMR,
pycnometry, and thermal analysis. The Ge–O coordination
number displays a broad maximum nGeO = 4.14(3) close to 27
mol\% PbO. This is smaller than the maximum nGeO = 4.3
reported in CaO–GeO$_2$ glasses but occurs at a similar
composition. This structural behavior appears to explain the
relatively weak germanate anomaly manifest in lead germanate
glasses, for example as a maximum in the measured atom
number density and a plateau in the glass transition
temperatures. The structural role of Pb(II) is complex. On
the one hand, short covalent Pb–O bonds and small Pb–O
coordination numbers of ∼3 to 4 indicate glass network
former character for Pb(II), associated with a
stereochemically active electron lone pair. On the other
hand, the presence of some GeO$_5$ or GeO$_6$ units, in
addition to the majority GeO$_4$ tetrahedral species,
indicates some modifier character of Pb(II) at low PbO
contents, giving rise to the observed weak germanate
anomaly, as well as elongation and enhanced ionicity of the
Pb–O bonds. Overall, the observed structural behavior of
Pb(II) in lead germanate glasses appears as intermediate
between that observed in lead silicate and lead borate
glasses. Despite rapid quenching, at low PbO contents, the
glasses studied exhibited nanoscale heterogeneity, evidenced
by small-angle X-ray scattering consistent with the early
stages of spinodal decomposition.},
cin = {DOOR ; HAS-User},
ddc = {660},
cid = {I:(DE-H253)HAS-User-20120731},
pnm = {899 - ohne Topic (POF4-899)},
pid = {G:(DE-HGF)POF4-899},
experiment = {EXP:(DE-H253)D-BW5-20150101},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000710191700001},
doi = {10.1111/jace.18166},
url = {https://bib-pubdb1.desy.de/record/473934},
}