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Co-57 Decay for Solid State Physics

#1219


Study of Aftereffects of Nuclear Decay of Co-57 in Cobaltates and Ferrates of Rare earth Elements to Expand the Advantages of the Emission NGR Spectroscopy in the Investigation of Complex Oxides of Rare Earth and Transition Metals and Prediction of Proper

Tech Area / Field

  • PHY-SSP/Solid State Physics/Physics
  • PHY-ANU/Atomic and Nuclear Physics/Physics

Status
3 Approved without Funding

Registration date
11.02.1998

Leading Institute
Khlopin Radium Institute, Russia, St Petersburg

Collaborators

  • Bundesanstalt für Materialforschung und prüfung, Germany, Berlin\nUniversity of Tokyo / School of Engineering, Japan, Tokyo

Project summary

The principal goal of the program is the study of aftereffects of nuclear decay of 57Co in cobaltates and ferrates of rare earth elements and the comparative analysis of these data with the results of the absorption NCR measurements aims to develop the advantages of the emission Mossbauer spectroscopy in the investigation of complex oxides of rare earth and transition metals and in nanotechnology.

Mossbauer spectroscopy is one of the most sensitive physical methods of determination of spin state and electronic configuration of elements in solids. It has been successfully used in the investigation of transition metal states in complex oxides, in particular, the valence of copper in HTSC-ceramics. The vast of such measurements were made using the absorption NGR spectroscopy, which has several obvious pitfalls that distorts the final results. To measure the absorption NGR spectrum the substance being investigated must be doped with iron-57 in quantities reaches several at.% of the studied metal (for example, copper) content. Such quantities of the impurity atoms differing widely in atomic radii and, in some cases, in valence state strongly deform the crystal lattice and hence distort the resultant spectrum. Keeping in mind vigorous development of nanotechnologies operating with nanometer particles such levels of doping is simply unacceptable.

The principal advantage of the emission NGR spectroscopy is the miserable doping level. The weight of the 57Co impurity is less than 1 microgram. But in 57Co doped matrixes arise problems with aftereffects of 57Co nuclear decay. The literature data about the aftereffects of 57Co nuclear decay in complex oxides are fragmentary and non systematic A great efforts will be undertaken in studying the formation of phases in the Ln-Co-O system (Ln - rare earth element) where the existence of some cobaltates is still uncertain.

A particular attention is planned to be paid to the emission spectra of rare earth's cobaltates and ferrates labelled with 57Co: the determination of spin and valence states of Fe and Co atoms and the role of rare earth cations on the local symmetry and nuclear isomer shifts of the resonance lines. For these purposes the unique measuring devices, developed in Radium Institute - resonance scintillation detectors (RSD) will be used. Application of RSD enables to get rid of very time consuming procedure of resonance measurements with single line absorber. The use of RSD instead of ordinary Nal(TI) detector makes it possible to obtain emission spectrum with good statistics directly without standard single line absorber for several hours.

Special attention will be focused on the careful measurements of the absorption spectra of rare earth ferrates and cobaltates doped with 57Fe.

The final stage of the program is the detailed comparative analysis of parameters and tendencies obtained by means of the emission and absorption NGR measurements in isomolecular cobalt and iron containing compounds.

The following methods will be used for the realisation of the project: most up-to-date chemical, radiochemical and g-spectroscopic analysis, X-ray phase analysis, thermogravimetry, emission and absorption NGR spectroscopy.

As a result of realization of the project the initial data will be obtained and thoroughly analysed to make a conclusion about the possibility of correct application of the emission Mossbauer spectroscopy in further investigations of complex oxides of rare earth and transition metals and give the recommendations for the correct application.

The participation in the project of weapons scientists, engineers and technicians allows reorientating their activity to peaceful tasks concerned with the developing of physical methods of investigation of solids.


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