Abstract
Profiled Al2O3 single crystals grown by Stepanov’s method to obtain anion-deficient composition were characterized by neutron diffraction at T=300 K for the first time. Whereas the main structure motif of investigated crystals is checked to be of corundum-type, the scattering pictures of as-grown crystal demonstrate pronounced anomalies being probably indications on substructure forming. However, neutron scanning of synthesised crystal taken after annealing under restoring conditions reveals additional effects associated with displacement type superstructure.
Highlights
There is considerable interest in the refractory compounds to be adapted for a range of high-temperature and nuclear applications, variations of sintered corundum, or Al2O3, belong to large group of these numerous materials [see 1-3 and refs therein]
Major features of the idealized structure model identified by visible main Bragg peaks of thermal neutron diffraction allow the adequate adjustment of appropriate volume α-Al2O3 single crystals for neutron diffraction experiments
As it was checked by neutronographic characterization, corundum structure is the main structure motif of both crystals
Summary
There is considerable interest in the refractory compounds (mainly oxides) to be adapted for a range of high-temperature and nuclear applications, variations of sintered corundum, or Al2O3, belong to large group of these numerous materials [see 1-3 and refs therein]. In idealized model, represented by space group R-3c (trigonal syngony) the α-Al2O3 structure may be described as a slightly distorted hexagonal close-packed arrangement of oxygen ions (O2-), with interlayer coordinations related to displacements of aluminium atoms. Profiled anion-deficient single crystals of corundum (α-Al2O3-δ) grown by Stepanov’s method under reducing conditions are widely used for the manufacture of radiation detectors of the type TLD500 and Al2O3:C [7]. The presented work is devoted to neutronographic characterization of structure states of aniondeficient corundum single crystals grown by Stepanov’s method; another purpose in view - to check. Published under licence by IOP Publishing Ltd whether structure vacancies of anion-deficient corundum are possible to form any superstructures after restoring anneal of α-Al2O3-δ crystals
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