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High Fraction of Penta‐Coordinated Aluminum and Gallium in Lanthanum–Aluminum–Gallium Borates
Author(s) -
Turcu Flaviu R. V.,
Samoson Ago,
Maier Maria,
Trandafir Diana L.,
Simon Simion
Publication year - 2016
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.14265
Subject(s) - gallium , fourier transform infrared spectroscopy , boron , amorphous solid , lanthanum , aluminium , materials science , analytical chemistry (journal) , magic angle spinning , tetragonal crystal system , crystallography , x ray crystallography , chemistry , nuclear chemistry , nuclear magnetic resonance spectroscopy , crystal structure , inorganic chemistry , diffraction , metallurgy , stereochemistry , chemical engineering , physics , organic chemistry , optics , chromatography , engineering
This study is focused on structural changes induced by increasing treatment temperature of sol‐gel–derived La 2 O 3 ∙Al 2 O 3 ∙Ga 2 O 3 ∙5B 2 O 3 system. The structure of samples heated for 30 min up to 900°C was investigated by X‐ray diffraction ( XRD ), Fourier transform infrared ( FTIR ) spectroscopy, and magic‐angle spinning nuclear magnetic resonance ( MAS ‐ NMR ) analysis of 27 Al, 11 B, and 71 Ga nuclei. The vitreous structure is preserved inclusively after 800°C treatment, and starting with 850°C the only crystalline phase evidenced in XRD patterns is of LaAl 2.03 B 4 O 10.54 type, of La(Al,Ga) 2.03 B 4 O 10.54 composition. The FTIR results point out the presence of BO 3 , AlO 4 , and AlO 6 , and starting with 800°C treatment also of BO 4 and AlO 5 structural units, but more detailed information related to boron, aluminum, and gallium environments is obtained from the analysis of MAS ‐ NMR data. These data evidenced in both amorphous xerogels and in crystallized samples a high fraction of penta‐coordinated aluminum and gallium.