PROTON MAGNETIC RESONANCE
AND THE STATE OF HYDROGEN IN BERYLLIUM HYDROXIDE
R. N. Pletnev,
V. S. Kiiko,
Yu. N. Makurin,
and A. A. Nepryakhin
Translated from Novye Ogneupory, No. 7, pp. 39 – 41, July, 2005.
Proton magnetic resonance spectra of beryllium hydroxide b-Be(OH)
and products of its thermal decomposi
tion are studied at room temperature and 123 K. It is shown, based on these spectra and differential thermal
analysis and x-ray diffractometry data, that, heated to above 500 K, b-Be(OH)
decomposes into a finely dis
persed BeO and H2O to convert finally to an amorphous beryllium oxyhydroxide. At above 600 K, a crystal
line BeO is formed involving dehydration of the finely dispersed BeO and amorphous oxyhydroxide phase.
In recent years, the interest in beryllium oxide was
mainly focused on experimental and theoretical studies of its
chemical bond and point defects (for example, [1 – 3]). Still,
BeO is likewise an object of interest in a practical aspect. Ce-
ramics based on BeO exhibit unique properties combining
high chemical, thermal, and radiation resistance and heat
conductivity, which makes it effective for use in nuclear en-
gineering and electronic industry [4 – 6].
A common technique for preparation of BeO is thermal
decomposition of beryllium hydroxide; therefore it would of
interest to gain a deeper insight into physicochemical charac-
teristics and bond – structure relationships in the initial be
ryllium hydroxide and its heat-treated products.
Our goal was to conduct such a study using proton mag
netic resonance (PMR), differential thermal analysis (DTA)
and x-ray diffractometry methods.
was prepared by hydrolytic de
composition of a dilute sodium beryllate solution . The
DTA curves of beryllium hydroxide were recorded on a Du
Pont instrument in air under normal pressure in the tempera
ture range of 300 – 1470 K. The PMR signals were recorded
on a broad-line spectrometer in a magnetic field of about
20.4 kHz at room temperature and 123 K. The modulation
amplitude did not exceed 0.9 Hz, the number of passages
through resonance was 10. The x-ray diffraction analysis of
powdered beryllium hydroxide was carried out on a
DRON-2 diffractometer using CuK
RESULTS AND DISCUSSION
Thermal decomposition of beryllium hydroxide in air
produces a strong endothermal effect in the range of
480 – 620 K with a peak at 555 – 565 K. In the range of
290 – 520 K, four weak endothermal peaks at 323, 368, 438,
and 488 K are observed that correspond to the removal of
small amounts of sorbed gases, physically and chemically
bound water. The main peak at 555 – 565 K is assigned to
the loss of constitution water. The removal of oxyhydride
groups from beryllium hydroxide occurs mainly in the range
of 480 – 620 K; still, the process does not finish completely
even at a temperature as high as 1270 K. The formation of
water at temperatures above 5620 K is mainly associated
with dehydroxylation considering that the hydrate shell of
BeO (thermally stable at above 620 K) is composed of
hydroxyl groups tightly bound to the surface species of pow
dered BeO by coordinately unsaturated beryllium atoms .
To identify the features observed, proton magnetic reso
nance (PMR) spectra were recorded. At room temperature,
the resonance signal from the initial beryllium hydroxide
(identical to the signal from specimen No. 2) is the superpo
sition of two features — a broad signal with the width
DH = 11 Hz and a narrow weak signal (see Fig. 1).
The origin of narrow singlets (whose width is controlled
by the modulation amplitude) is associated with H2O mole
cules which either migrate over the surface, or are localized
at structural imperfections; thus involved, the H2O mole
Refractories and Industrial Ceramics Vol. 46, No. 4, 2005
1083-4877/05/4604-0273 © 2005 Springer Science+Business Media, Inc.
Ural Branch of the Russian Academy of Sciences, Ural State
Technical University (UGTU-UPI), Ekaterinburg, Russia.