Fe - Impurity Studies

Measurement of the energy of a y-ray emitted (or absorbed) in a recoilless event registers information only about the immediate chemical environment of the emitting (or absorbing) nucleus. Mdssbauer experiments are performed by comparison of a source and an absorber, and it is usual to utihse a source without hyperfine effects as a reference standard for a series of absorber experiments. This is not the only option available, however. If we use a reference absorber, it is possible to study hyperfine effects in the source. These are produced by the chemical environment in which the excited-state Fe nucleus finds itself when it is generated in the source matrix. The total concentration of the Co parent atoms is very small indeed, and each atom can therefore be considered as an isolated impurity in the source matrix. 

Some interest has also centred on the Co doping of iron and cobalt compounds, although this technique is probably not so useful because of the unpredictable chemical effects of the Co decay. The doping of non-iron compounds with enriched Fe is also discussed where appropriate. 

Also included for convenience in this chapter is a small section on miscellaneous applications of Mossbauer spectroscopy to subjects such as surface states, chemical reactions, and diffusion in liquids, which are of chemical interest but do not as yet represent major areas of study. 

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LOCAL RELAXATION FOR AND FE IMPURITIES IN FLUOROPEROVSKITES DENSITY FUNCTIONAL STUDY... 

Stefeniuk, 1., Rudowicz, C, Gnutek, P., and Suchocki, A. (2009) EPR study of Cr and Fe " impurity ions in nominally pure and Co -doped YAIO3 single crystals. Appl. Magn. Reson., 36, 371-380. 

The method can successfully be used in analyses of impurities in metals and alloys, for estimation of minor elements in monomolecular films of oxide layers of Fe-Cr-Ni alloys, for detection of metal impurities in environmental pollution, for studying the depression of high-grade semiconducting materials and for analysis of the corrosion products of contact junction diodes used in microelectronic circuits. Much sophistication is desirable on the instrumental side so as to incorporate an automatic recording device to make an FR polarograph suitable for wider applications and common use. 

The moist sulfide readily oxidises in air exothermally, and may reach incandescence. Grinding in a mortar hastens this [1]. The impure sulfide formed when steel processing equipment is used with materials containing hydrogen sulfide or volatile sulfur compounds is pyrophoric, and has caused many fires and explosions when such equipment is opened without effective purging. Various methods of purging are discussed [2], Formation of pyrophoric FeS in bitumen tanks is considered as a cause of spontaneous ignition and explosion in the head space [3], A detailed study of formation of possibly pyrophoric sulphides from rust in crude oil tankers has been made [4],... 

Steady-state luminescence of feldspars is well studied. The following impurity centers have been found Tl, Pb, Pb, TR + (Ce, Dy, Sm, Tb, Nd), Eu +, Mn +, Fe, Cr (Tarashchan 1978 Walker 1985 Bakhtin and Moroshkin 1986 White et al. 1986 Kuznetsov and Tarashchan 1988 Waychunas 1989 Gotse 2000 Correcher and Garcia-Guinea 2001 Gorobets and Rogojine 2001 Krbetschek et al. 2002). 

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