The optical and Fe-57 Mossbauer spectra of lithium diborate (Li2B4O7) in
borophosphate glass-ceramics
PHYSICA B-CONDENSED MATTER, 322 (3-4):
276-288 (2002)DOI: 10.1016/S0921-4526(02)01194-8
Abstract
In this paper lithium borophosphate glasses and glass-ceramics in the
system
66.6textbackslashxB(2)O(3textbackslash).(100-x)P2O5textbackslash
. 33.3Li(2)O:yFe(2)O(3) with 0 less than or equal to x less than or equal to 100 mol% and y = 4 mol%, were studied by X-ray powder
diffraction, Fe-57 Mossbauer and infrared spectroscopy. All the samples
in the system present a glass or glass-ceramics behavior which is
confirmed by X-ray diffraction. The substitution of p(5+) by B3+
associated with the increase of the ratio B2O3/P2O5 leads to oxidation
of the iron in the samples which was detected by Mossbauer spectroscopy.
From our Mossbauer analysis, high-spin Fe2+ and Fe3+ in a distorted
octahedral coordination are present in all samples. For heat-treated
samples we have the precipitation of crystalline phase of Li2B4O7 and
for others lithium borate phases which was confirmed by Xray powder
diffraction. The Mossbauer spectra for some heat-treated samples show,
besides the paramagnetic doublets, a magnetic sextet component with hyperfine magnetic field (B-hf = 50 T). These magnetic phases were not
identified up to this point in our study but we believe that these
parameters are quite close to Hematite (alpha-Fe2O3). The boric acid
phase H3BO3 were also identified by the X-ray diffraction, and infrared spectroscopy for x = 26.6, 40 and 53.3 mol%. Such glasses and
glass-ceramics containing nonlinear optical materials formed in a
controlled crystallization process would be interesting candidates for
application in new electro-optic devices. (C) 2002 Elsevier Science B.V.
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