Natural Wolframite, (Fe x Mn1−x )WO4 withx=0.95 to 0.41, obtained from seven different sites of two quartz-wolframites deposits of Degana and Sirohi in Rajasthan. India, have been studied by Mössbauer spectroscopy down to 20 K. X-ray diffraction studies with a monochromatic Cu radiation (λKa-1.5405 Å), were carried out to determine the value ofx. The Mössbauer spectra of all seven samples were recored at 300, 200, 100, 50, 40, 30 and 20 K, and were least square fitted for different sites. The Mössbauer parameters are attributed to a high spin ferrous ion in a quite distorted octahedral symmetry, and only one sextet has been resolved below transition temperature.

Iron-57 Mössbauer spectroscopy has been employed for the identification of iron phases present in coal ash obtained from the Panipat thermal power plant. The Mössbauer data, recorded at room temperature and interpreted by computer, indicate the presence of hematite, magnetite and mullite silicate glasses in all samples of the ash. Further, these results have been corroborated with X-ray diffraction, susceptibility measurements, and chemical analysis.

Powdered samples of Indian Natural Wolframites, (FexMn1−x) WO4 with x=0.95 to 0.41, obtained from seven different locations of two quartz-wolframite deposits of Degana and Sirohi in Rajasthan, have been investigated by Mössbauer spectroscopy down to 20K and magnetic susceptibility down to 77K. The Mössbauer spectra from 300K to 30K clearly indicate multiple sites which is at variance with the reported work. Below 50K a weak magnetic interaction with Hint∼45Koe is observed. The spectra above transition temperature are resolved in three doublets and explained on the basis of reported crystal structure. The values of isomer shift, quadrupole splitting and magnetic hyperfine field have been attributed to high spin ferrous ions with octahedral symmetry. Relatively small value of Q.S. (∼1.5 mm/sec. at 300K) indicate a strong contribution of the lattice term to the electric field gradient.

X-ray diffraction, bulk magnetization, and $^{57}\mathrm{Fe}$ M\"ossbauer spectroscopic measurements on ${\mathrm{Fe}}_{1+\mathrm{x}}$Sb system for various values of x (0.14\ensuremath{\le}x\ensuremath{\le}0.35) are reported. The x-ray data suggest that the ASTM (American Society for Testing and Materials) data file for ${\mathrm{Fe}}_{1+\mathrm{x}}$Sb should be modified. The lattice N\'eel temperatures obtained from magnetic susceptibility and M\"ossbauer spectroscopic measurements are in nice agreement with each other and decrease linearly with increase in x. The N\'eel temperatures for the ordering of interstitial Fe atoms are higher than 60 K and increase with x. The low-temperature M\"ossbauer spectra have been analyzed in terms of a Lorentzian distribution of the magnetic hyperfine field at lattice sites, a low-field site, and a relatively high-field interstitial site. Also included are comments on the low magnetic moment of Fe in ${\mathrm{Fe}}_{1+\mathrm{x}}$Sb.

Low temperature 57Fe Mössbauer spectroscopic studies on CaO(Fe2O3)1−x(Al2O3)x, written as CF1−xAx, have been carried out. In view of the earlier findings based on room temperature data, the spectra have been analysed by assuming three Fe sites: two belonging to CF phase and the third site for the Fe atoms distributed in the CA phase. The Fe sites pertaining to the CF phase experience hyperfine field of about 49T and 47T, respectively, at 20K; whereas the third site is paramagnetic at this temperature.

The Mössbauer spectroscopic and x-ray diffraction investigations have been carried out on a variety of ordinary portland, portland pozzolanic, portland slag and sulphate resisting portland cements, using dry as well as hydrated samples. The discussion of the Mössbauer parameters shows that Fe atoms occupying distorted octahedral and tetrahedral sites in the dry cements are hydrated to form ferrite monosulphate without producing Fe(OH)3 and its gel; hydration of the slag cement proceeds much faster than other cements; and that the composition of the iron-bearing phase in the sulphate resisting portland cement, studied in detail, is close to C4AF.

The iron-antimony system, which occurs in a Ni-As structure, shows interesting magnetic properties and has been investigated by several workers. In order to explore these properties further, we have studied ${({\mathrm{Fe}}_{1\ensuremath{-}y}{\mathrm{Ni}}_{y})}_{1+x}\mathrm{Sb}$ by x-ray diffraction and M\"ossbauer methods in the concentration ranges $0.02\ensuremath{\le}y\ensuremath{\le}0.42$ and $0.08\ensuremath{\le}x\ensuremath{\le}0.16$. Through analysis of the x-ray data, it has been found that these samples are isotypic with ${\mathrm{Fe}}_{1+x}\mathrm{Sb}$, wherein Fe is substituted by Ni, and that the American Society for Testing and Materials data file for ${\mathrm{Fe}}_{1+x}\mathrm{Sb}$ needs modification. Using M\"ossbauer spectroscopic measurements in a transmission geometry at different temperatures, we have determined the N\'eel temperatures, which decrease linearly with increasing $y$. The substitution of Ni atoms in the Fe-Sb lattice produces two new magnetic hyperfine fields which are about 40% and 80% lower than the original field in Fe-Sb. The magnitude of these fields is independent of Ni concentration, whereas the density of sites with these fields increases monotonically with the increase in $y$.

An experimental study of the vacancy distribution in pyrrhotite (Fe1–xS) is presented. Seven samples from various deposits in India are investigated using Mössbauer spectroscopy, X-ray diffraction, and thermo-magnetic analysis techniques and a partially ordered and partially random vacancy distribution model for intermediate pyrrhotite is discussed. Experimentelle Werte der Leerstellenverteilung in Pyrrhotit (Fe1–xS) werden mitgeteilt. Sieben Proben aus verschiedenen Lagerstätten in Indien werden mit Mößbauerspektroskopie, Röntgenbeugung und thermomagnetischer Analyse untersucht und ein Modell teilweise geordneter und statistisch verteilter Leerstellen für Zwischenpyrrhotit diskutiert.

The Mössbauer spectroscopic investigations of dry sample of Indian high alumina cement (HAC) show that Fe2O3 occurs in the CF, CA and C2F1−xAx phases. The presence of CF component in this cement is being reported for the first time and its unambiguous detection has been made possible by the selectivity of Mössbauer spectroscopy. The spectra of hydrated HAC have been discussed in terms of hydration of the above mentioned compounds. The X-ray diffraction studies of dry as well as hydrated HAC are also included.

The members of the ferrite series CF1−1Ax and with O ⩽ × ⩽ 0.8 have been studied by x-ray diffraction and Mössbauer spectroscopic techniques. The observed Mössbauer parameters are explained in the light of the following model, which is supported by the x-ray data. For non-zero x, the two phases CF and CA co-exist such that Al and Fe are distributed in these, respectively. With increase in x, the CF phase decreases and the CA phase increases.

The ternary systems Fe0.968−xMnxSi0.032 with 0 ≦ x ≦ 0.082 are studied for their mechanical, magnetic, and Mössbauer properties at room temperature. The trend shown by the hardness, the relative Mössbauer peak areas, and the intensities of the Mossbauer spectra for different Fe sites are indicative of short-range order and it is found that the intensities are best explained when impurity-impurity separation is restricted to a √3. The observed variations in the central shift and magnetic hyperfine field are attributed to the 4s band contribution of Mn atoms. Die ternären Fe0,968-xMNxSi0,032-Systeme mit 0 ≦ x ≦ 0,082 werden hinsichtlich ihrer mechanischen, magnetischen und Mößbauer-Eigenschaften bei Zimmertemperatur untersucht. Der durch Hürte, der relativen Flächen der Mößbauermaxima und den Intensitäten der Mößbauerspektren für verschiedene Fe-Plätze nachgewiesene Trend weist auf Nahordnung hin und es wire gefunden, daß die intensitäten am besten erklärt werden können. wenn der Störstellen-Störstellen Abstand auf a √3 begrenzt ist. Die beobachteten Änderungen der zentralen Verschiebung und des magnetischen Hyperfeinfeldes werden den Beiträgen der Mn-Atome zum 4s-Band Zugeordnet.

An experimental study of the oxidation of Indian natural pyrites is presented here. Three pyrite samples, two obtained directly as mineral fractions from the ores of Amjhore and Deri and third as a constituent of coal from Talchir, have been studied by Mössbauer spectroscopy after heating at different temperatures in air. Mineralogical, chemical and infrared absorption analyses have also been carried out. In all three cases, the first product of oxidation observed is sulphate instead of α-Fe2O3. The oxidation is seen to proceed in the sequence FeS2 → FeSO4 · 7 H2O → α-Fe2O3 and/or Fe2(SO4)3 → α-Fe2O3. The start of the thermal decomposition in these samples has been found to be governed by the degree of crystallinity, whereas complete conversion to α-Fe2O3 is observed to depend upon the particle size and the carbonaceous matter and sulfur contents.

The infrared and Mössbauer spectroscopic studies have been carried out for dry and hydrated samples of Indian Ordinary Portland Cement and Portland Pozzolana Cement. The infrared wavebands have been assigned and discussed in the light of available literature. The Mössbauer data show that iron occurs as Fe3+ and occupies two sites with 6 and 4 coordinations and that hydration of cement renders the conformation around Fe atoms more symmetric. The possibility of formation of Fe(OH)3 and its gel is also excluded on the basis of the values of Mössbauer parameters.