Metals and Ceramics Division Annual Progress Report for Period Ending June 30, 1967. Page: 84 of 300
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57
formation of crystals of the complex disordered
phase previously described7 as 3BeO.2Sr0.
We have grown crystals of the 4BeO.SrO equilib-
rium phase6 and have observed x-ray diffraction
data in good agreement with powder data reported8
for a phase called Sr2Be 0 formed by heating
coprecipitated hydroxides. The phase crystallizes
in the hexagonal system, Laue group 6/mmm, with
unit cell parameters a0 = 4.5961 0.00004 A,
co = 8.9300 0.0001 A. Reflections hhl with I
odd are systematically absent, indicating a c-glide
in the ac plane. Reflections hkl are absent if
h - k = 3n and I is odd; this is a non-space-group
extinction caused by special atom positions in the
unit cell. Crystals show a pyroelectric effect
normal to the c-axis. The most probable space
group is therefore P62c. The unit cell parameters
are related to those of BeO in that a - /3aBe
and c0 2 2cBeo. A set of Cu Ka and -0 reflec-
tion intensity data has been collected and a
structure analysis begun.
Sodium Beryllium Oxide
Mixtures of 60 mole % BeO, 40 mole % Na20 (in-
troduced as Na2CO3) were heated on a platinum
strip in air to about 1300 C. A molten phase
separated from the mixture. On quenching, this
liquid solidified to an optically isotropic clear
material that produced no sharp crystalline x-ray
diffraction pattern. Qualitative electron micro-
probe and spectrographic analyses of a piece of
the glasslike material showed only sodium and
beryllium as major metallic constituents. The
phase is attacked by atmospheric moisture at room
temperature after 24 to 48 hr.
Other Systems
We are attempting to prepare mixed oxide com-
pounds in the systems BeO-BaO, BeO-Nd203, and
BeO-Ho 203. Crystals of additional phases in the
BeO-Y203 and BeO-La203 systems will also be
studied in an effort to determine factors governing
the formation of stable and metastable compounds.
IL. A. Harris and H. L. Yakel, Acta Cryst. 15, 615-
16 (1962).
8R. A. Mercer and R. P. Miller, J. Inorg. Nucl. Chem.
28, 61 (1966).We have been able to grow small imperfect crys-
tals of the 3Be0-BaO compound reported by
Isupova and Keler.9 Preliminary diffraction re-
sults suggest a monoclinic unit cell and are in
agreement with the powder data published by the
Russian workers.
X-RAY DIFFRACTION FROM
NE UTRON-IRRADIATED CERAMIC
SINGLE CRYSTALSH. L. Yakel
G. W. Clark0
We conducted an irradiation experiment in which
a variety of crystals of a ceramic nature were ex-
posed to neutron irradiation in the Engineering
Test Reactor.' 1 Dose levels of 4 x 1020, 8 x 1020,
and 10 x 1020 neutrons/cm2 ( 1 Mev) were achieved,
as measured by flux monitors. The irradiation
temperature was 140 20 C. Crystals included
in this experiment were BeO, Al203, MgO, "spinel"
(MgAI204), Si02, Si, Ge, SiC, and beryl (Be3Al2
Si6018). Results of x-ray diffraction experiments
with the irradiated BeO crystals have been re-
ported. 12
In the period of this report, we completed pre-
liminary studies of the irradiated "spinel" crys-
tals. Determination of the lattice parameter of an
unirradiated control crystal demonstrated that the
composition is approximately MgO.3A1 03 rather
than the ideal 1:1 spinel composition.' There
is no evidence of ordering of the lattice defects
(probably anion and cation vacancies) that are
required by the 1:3 stoichiometry.
The irradiated crystals were only slightly more
yellow than the unirradiated controls. Rotation
and Weissenberg diffraction patterns obtained
from them showed reflections very little broader
than those on similar patterns of unirradiated
crystals. Fractional lattice parameter variation
as a function of neutron dose is shown in Fig.
9E. N. Isupova and E. K. Keler, Zh. Neorgan. Khim.
9, 394-402 (1964); Russ. I. Inorg. Chem. (English
Trans1.) 9, 217-21 (1964).
10Crystal Physics Group.
1'The experiment was possible through the coopera-
tion of G. W. Keilholtz and R. E. Moore of the Reactor
Chemistry Division, who permitted us to place crystals
in their experiments at the ETR.
12H. L. Yakel, Metals and Ceramics Div. Ann. Progr.
Rept. June 30, 1964, ORNL-3670, pp. 57-60.
13F. Rinne, Neues Jahrb. Mineral. Geol. Palaeontol.
A 58, 43 (1928).
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Peterson, S. Metals and Ceramics Division Annual Progress Report for Period Ending June 30, 1967., report, January 1, 1967; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1030019/m1/84/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.