Mössbauer Effect Study of Iron Impurity States in AgCl and NaCl

Abstract

The analysis of the properties of Mossbauer spectra and the conditions of preparing crystals of AgCl and NaCl doped with 5 7 C~ enabled us to suggest microscopic interpretation for five different types of chemical associations of cobalt with vacancies and oxygen and OHimpurities. A change of charge from Fe++ to Fef+f and the reverse change were observed at high temperatures.Eine Analyse der MoDbauerspektren und der Priiparationsbedingungen von AgCl und NaCl, die mit W O dotiert wurden, armoglicht, eine mikroskopische Deutung fiir. fiinf unterschiedliche Typen chemischer Assoziate von Kobalt mit Leerstellen und Sauerstoffund OH--Defekten vorzuschlagen. Eine Anderung des Ladungszustandes von Fe++ nach Fe+++ und der umgekehrte Vbergang wurden bei hohen Temperaturen beobachtet.

The Mössbauer Emission Spectra of Impurity 57Cobalt in a Halide Matrix

“…Hennig and Kim Yung [15] claim that the large quadrupole splitting is due to a nearby oxygen anion, but it could equally be due to a nearby vacancy. On heating with H,O, Cl,, or 0,, the spectrum seen by other workers was seen.…”

“…In all cases the T o was introduced in the +2 oxidation state, but a signal corresponding to Fe2+ was seen in only one case [ E l , where very low concentrations were used, and the crystals were annealed and cooled very carefully in the absence of light. Hennig and Kim Yung [15] claim that the large quadrupole splitting is due to a nearby oxygen anion, but it could equally be due to a nearby vacancy. On heating with H,O, Cl,, or 0,, the spectrum seen by other workers was seen.…”

Deformation-induced mössbauer spectra in NaCl

“…According to the isomer shift systematics of Walker et al [7], these spectra have been attributed to trivalent, divalent, and monovalent iron respectively. The A-spectrum was interpreted as due to iron-vacancy complexes by Mullen [2], and to iron-oxygen complexes by Hennig and Yung [3]. The [3].…”

“…The A-spectrum was interpreted as due to iron-vacancy complexes by Mullen [2], and to iron-oxygen complexes by Hennig and Yung [3]. The [3]. I n the former case the spectrum is interpreted in terms of iron nuclides incorporated in a CoCl, precipitated phase, while in the latter case it is interpreted in terms of substitutional iron complexed with vacancies in the lattice.…”