X-ray micro- fluorescence, diffraction and absorption spectroscopy for local structure investigation of a radioactive zinc ferrite deposit Claude Degueldre * , Goutam Kuri, Camelia N. Borca, Daniel Grolimund NES, Paul Scherrer Institute, 5232 Villigen, Switzerland article info Article history: Received 26 February 2009 Accepted 23 April 2009 Available online 5 May 2009 Keywords: A. Zinc B. ASF B. XRD C. Oxide coating abstract X-ray micro- fluorescence (lXRF), diffraction (lXRD) and absorption spectroscopy (lXAS) techniques have been used to investigate the micro-crystalline and chemical structure of a radioactive zinc ferrite corrosion deposit phase formed on a zirconium dioxide substrate. Micro- fluorescence provides structural information based on the elemental distribution analysis, lXRD allows the determination of lattice parameters of crystalline compounds while lXAS yields data related to the atomic environment, such as coordination number and the distances to the nearest neighbours. The lXAS and the lXRD results are compared including a discussion of precision and accuracy of both techniques. Ó 2009 Published by Elsevier Ltd. 1. Introduction Synchrotron radiation techniques have been used in the last decades for characterising the atomic environment, hetero-struc- tures [1] or micro-features and submicro-phases [2] on/in various matrices. Films may currently be characterized by X-ray Absorption Fine Structure (XAFS) using a grazing incidence (GI) mode, e.g. [3], or in a Variable Incident Angle (VIA) XAFS mode to reveal the film internal structures [4]. These methods are very powerful and can be used to analyse phases in situ [5] in a versatile way. On the other hand the study may be performed in cross section of the film in reflection mode or through focussed ion beam thin sections in transmission mode [6]. A detailed analysis of the Extended X-ray Absorption Fine Structure (EXAFS) spectra and X-ray Absorption Near Edge Spectros- copy (XANES) spectra enables a better characterization of the amor- phous and crystalline structure of these films and provides a deeper understanding of the crystallization processes during growth. In the present study, X-ray micro-diffraction (lXRD) has been used to characterise the crystallographic phases of grains in the investigated film. Such local XRD has recently been performed on micro-features [7]. White beam pin-hole patterns of implanted lay- ers has been tested [8]. These investigations are based on Laue dif- fraction, a technique that profits of growing interest in the last few years [9]. This is due to the possibility of focusing the beam to micron size levels and to the performances of the latest lXRD detection and analysis methods. The combination of XRD and XAFS for thin film characteriza- tion has rarely been reported in the literature. The combination of these X-ray techniques was mainly used to investigate meso- porous silica films [10], the structure of a switchable mirror [11], or catalytic layers, e.g. [12]. The structure of oxide films prepared by various techniques such as ion beam induced chemical vapor deposition [13], sol–gel deposition [14], or heterogeneous deposition [15] were analyzed by XRD and EXAFS/XANES spectroscopy. Coprecipitated zinc ferrite [16,17] as well as thermochemically prepared samples [18] have also been studied by XAFS. The film structure may be analyzed and compared as a function of the prep- aration conditions. Here, a radioactive film of zinc ferritic spinel obtained as a cor- rosion product under hydrothermal conditions of a boiling water reactor on fuel rod has been analyzed by lXRF, lXRD and lXAFS for revealing the microcrystalline properties and the local environ- ment for the Fe (reactor steel main corrosion product) and Zn (additive) cations. The work is relevant since such deposit layers may affect the energy transfer from the fuel to the coolant and since the classical eddy current measurements of the corrosion layer may be falsified by the corrosion product deposit layers. It also completes some early work carried out on in situ characterisa- tion of corrosion layers on steel [19] and Zircaloy [20] in light water reactor conditions. Emphasis is given on the complementar- ities of these X-ray analytical techniques with respect to the num- ber of next neighbours, the atom distances and lattice parameters measured. In accordance with results on nano-sized ZnFe 2 O 4 , partial cation site inversion was observed in the investigated film, without a distinct change of the unit cell volume. 0010-938X/$ - see front matter Ó 2009 Published by Elsevier Ltd. doi:10.1016/j.corsci.2009.04.023 * Corresponding author. Tel.: +41 56 3104176; fax: +41 56 3106535. E-mail address: claude.degueldre@psi.ch (C. Degueldre). Corrosion Science 51 (2009) 1690–1695 Contents lists available at ScienceDirect Corrosion Science journal homepage: www.elsevier.com/locate/corsci