HAL Id: jpa-00218545
https://hal.archives-ouvertes.fr/jpa-00218545
Submitted on 1 Jan 1979
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
DEFORMATION INDUCED TEXTURE IN MÖSSBAUER ABSORBERS
D. Nagy
To cite this version:
D. Nagy. DEFORMATION INDUCED TEXTURE IN MÖSSBAUER ABSORBERS. Journal de
Physique Colloques, 1979, 40 (C2), pp.C2-49-C2-49. �10.1051/jphyscol:1979217�. �jpa-00218545�
JOURNAL DE PHYSIQUE Collogue C2, supplement au n" 3, Tome 40, mars 1979, page C2-49
DEFORMATION INDUCED TEXTURE IN MOSSBAUER ABSORBERSt
D.L. Nagy
Central Research Institute for Physios, H-1525 Budapest, P.O.B. 49, Hungary
Résumé.- Les anomalies observées dans les intensités des raies d'absorption Mossbauer pour des échan- tillons exposés à des pressions non hydrostatiques, sont attribuées à des effets de texture. Nous calculons l'influence sur la texture à la déformation de l'échantillon et de la forme des cristalli- tes. De la fonction de texture nous déterminons l'asymétrie d'une doublet quadrupole de 1/2+3/2. Nous discutons les possibilités d'éviter les effets de texture en spectroscopie Mossbauer et nous propo- sons une méthode pour préparer des absorbants exempts de texture.
Abstract.- Mossbauer absorbers subjected to (often unintentional) non-hydrostatic pressure may show pronounced texture. This is a geometrical consequence of deformation.
The texture function of a polycrystalline sample after deformation from the original height of unity to p was calculated supposing that the shape of the crystallites can be approximated by a cylinder of radius r and height h. From the texture function the asymmetry R=I7J./I0, of a 1/2-K3/2 quadrupole dou->
blet was calculated for the case of axially symmetric EFG and thin absorber : R = 3(1 +a) / (5 - 3a) where
1 p-2s(Arch ps//l - p- z s - 1) / (1 - p"2«) if -1 $ s < 0 a = J 1/3 if s = 0
(l-pSarc cos ps//I - pz s) / (1 - p2 S) if 0 < s <: 1
Here s is a shape parameter of the cylinder : s = (ir r-2h)/(ir r+2h) being -1 for a needle, +1 for a flake and 0 for a "cubic cylinder" (having cross-sections of the same area in two perpendicular di- rections like a cube).
For small deformations 6=l-p « 1 the asymmetry is : R = !+(2/5)s6+...
q
From the deformation dependence of R an effective shape parameter can be determined which characte- rizes the deformation-sensitivity of the investigated system. The evaluation of Ericsson and Wap- pling's data for chlorite /l/ yielded s = 0.12. For the systems FeC03 and FeSiFe.6H20 (both mixed with active carbon) the respective values s = 0.21 and s = 0.00 were found.
In the light of the above considerations the possibilities of avoiding texture effects in Mossbauer spectroscopy are discussed and a method is suggested for preparing texture-free absorbers.
Reference
/l/ Ericsson, T. and Wappling, R., J. Physique Colloq.
^7 (1976) C6-719.
+Applied Physics, \T_ (1978) 269.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1979217
