Fluorine modified oxide surfaces have received considerable attention both as research materials and as commercial catalysts. Pulsed NMR has been used to directly observe protons and fluorine on fluorine modified silica,alumina, and aluminosilicates. The center of mass of the 19F spectra is consistent with values reported for covalent siliconfluorine and aluminum-fluorine bonds. The proton and fluorine concentrations have been investigated as a function of sample preparation.

This paper is presented to illustrate the utility of Fe-57 Mössbauer spectroscopy in the physical and chemical characterization of metallic catalysts as a function of preparation and subsequent treatment. The particular example chosen for investigation is the Ru-Fe bimetallic salt system which has significant potential as an active Fischer-Tropsch catalyst. The interpretation of the resulting Mössbauer parameters provides information on the chemical state of the metals as a function of treatment and initial salt properties and allows certain deductions to be made about particle size and solid state properties.

Mössbauer effect measurements have been taken of iron and tin introduced into brown coal to act as catalysts for hydrogenation. Spectra taken with 119Sn show that after introduction from solution, the tin appears as SnO2. During subsequent hydrogenation in an autoclave, some of the SnO2 is converted to β-tin and SnS. Ion-exchanged iron is shown from 57Fe measurements to occupy at least one site not populated in the native coal. Line broadening in this site and the other two original sites indicate the existence of variations in the local environment.

We measured the temperature dependence of T1 in a Mg-stabilized single crystal of Na β”-alumina. A comparison with earlier measurements on Li-stabilized polycrystalline samples indicates that, below 500K, the sodium ion kinetics are not directly affected by the stabilizing element. Above 500K our measured T1 shows a dependence on sample composition. Observations of NMR linewidth and signal intensity vs. water content indicate that, at low water concentration (< 2%), all sodium is in contact with water in its conduction plane; at higher water concentrations, the additional water may be forming complexes with some of the sodium.

We present an NMR study of sodium motion and distribution in Na β-alumina below 160K. The 23Na lineshape shows that a rearrangement of sodiums occurs near 100K. Below this “transition”, a fraction of the sodium ions undergo a local motion that is an efficient mechanism for 23Na spin-lattice relaxation in the interval 50÷80K. This motion does not have a major influence upon the 27A1 relaxation. Below 50K the low-lying excitations typical of glasses control the spin-lattice relaxation processes of 27AI and, to a certain extent, 23Na.

This paper presents a NMR study of mixed alkali effects in δ-aluminas. It is shown that the BPP theory of relaxation does not describe the NMR results. However, with an elementary analysis of the data, NMR yields information about the cation dynamics which substantially agrees with the diffusion measurements.

We have examined the electronic susceptibility of intercalated graphite and doped (CH)x using ESR [1]. The dopant in both cases was AsF5. For metallic intercalated graphite and for heavily doped (CH)x, the low frequency Schumacher-Slichter technique was used to determine the density of states at the Fermi energy. In the case of doped (CH)x, susceptibility measurements as a function of temperature allowed separate determination of the Curie and Pauli contributions.

We have used the 57Fe Mössbauer effect to study the electronic spin configuration of Fe substituted in the layer compound LixTal-yFeyS2(0≤x≤l;0≤y≤0.1). The Mössbauer effect results show that the Fe is localized and in Fe2+ valence state but the electronic configuration depends on the lithium concentration. At room temperature the isomer shift of Fe2+ increases from 0.56 mm/s for x = 0 (no Li) to 0.77 mm/s for x = .86 (at y = 0.05). The isomer shift results reflect the changes in the electronic configuration of the host from Ta4+(5d1) to Ta3+(5d2) and an increase in ionicity as the lithium content increases from 0 to 1.

There are only a few Fe-based compounds which are superconducting since the depairing of Cooper pairs is unavoidable in the presence of an Fe moment. In Sc2Fe3Si5 and Th7Fe3, Mössbauer measurements on 57Fe show that there is no magnetism at the Fe site in either compound. The isomer shift values indicate the reason behind this identical magnetic behavior to be quite different in its electronic origin.

Electron spin resonance (ESR) of dilute paramagnetic ions in nonmagnetic metallic hydrides provides microscopic information about the hydrogen ions in the immediate vicinity of the impurity. By comparing ESR spectra for different host metals and several hydrogen/metal ratios, one can determine material properties including host lattice symmetry, phase boundaries and occupation of available sites by hydrogen. Examples are presented of ESR of dilute Er in group IIIB and IVB metal hydrides, demonstrating the sensitivity and versatility of ESR as a spectroscopic technique.

The hydrogen rich ternary hydride phases of RFe2Hx (R=Y Dy, Er) with x>4 have been investigated using 57Fe, 161Dy and 166Er Mössbauer spectroscopy and bulk magnetization. In all cases, the presence of hydrogen results in a dramatic reduction in the moment on Fe as well as the magnetic transition temperature. The data also imply a simultaneous weakening of the R-Fe magnetic exchange.

Measurements of T1 (Bo = 0.94T), and T1r as a function of temperature have been carried out on a LaNi5H7 sample at 4 different rotating magnetic field values. The T1 and T1r data are consistent with earlier data by Karlicek and Lowe [3,4], in which an asymmetry in the slopes of the log T1r vs. T−1 plot was found. The new data has been analyzed assuming a spectral density function J(ω,τc) of form J(ω, τc) = A(τc)B(Ω)F(ωτc), with τc = τc∞ exp(Ea/kT). This assumption leads to a spectral density function that fits all our data well, with Ea = 39 KJ/gm-Atom H, and J(ω)∼ Wω−1.35 in the high frequency limit. This Ea agrees well with the Ea obtained from diffusion constant measurements.

NMR data are presented for reactively sputtered amorphous silicon-hydrogen alloys (a-Si(H)). Measured differences in two of the samples are attributed to two distinct morphologies: a mixed phase (monohydride and dihydride) and a purely monohydride composition. Features of the mixed phase morphology have been modeled. Room temperature, 35 MHz spin-lattice relaxation times are presented for a series of monohydride samples prepared with systematically varied sputtering parameters. A correlation of proton T1 with the density of ESR states tentatively is suggested.

Proton magnetic resonance data are presented for the hydrogen alloys of plasma-deposited amorphous boron, silicon, carbon, silicon carbide, and silicon nitride. Linewidth and lineshape analysis leads to the conclusion that hydrogen nuclei are clustered in a-Si/C:H, a-C:H, and a-Si/NiH. The a-Si/C:H and a-C:H data show that hydrogen exists in two phases. Modeling of linewidths in a-Si/C:H indicates that the two phases are heavily hydrogenated carbon clusters imbedded in a weakly hydrogenated silicon lattice. Evidence is also presented for the presence of motionally narrowed hydrogen spectra in a-B:H, a-Si/N:H and a-C:H. “B NMR spectra in a-B:H show no evidence of motional narrowing. It is suggested that the hydrogen nuclei giving rise to the motionally narrowed spectra are associated with disorder modes.

Mössbauer spectroscopy was used to study the lattice location of Fe in Si. Strikingly different spectra were recorded depending on the implantation dose and implantation temperature. Drastic changes were also observed in the spectra upon thermal treatment or laser irradiation of the samples. Implantation profiles of several of these sources were also measured. Laser irradiation and thermal annealing above 400° C results in surface segregation of the implanted 57 Co activity.

We have deposited the Mössbauer isotope Fe 57 on (111) Si surfaces at room temperature and measured the Mössbauer spectrum using conversion electron Mössbauer spectroscopy for enhanced surface sensitivity. Samples were examined as a function of substrate preparation and thermal anneal. Rutherford backscattering was used to monitor sample preparation. The Fe 57 layers have been coated with natural iron (2.2% Fe 57) or silver to prevent them from oxidizing when exposed to air. The known distinctive Mössbauer spectra of Fe, FeSi, FeSi 2 , Fe in Si, and Si in Fe allows the identification of these phases in the samples.

The laser annealing behaviour of Te-implanted GaAs, GaSb, GaP and InP has been studied by Mössbauer Spectroscopy. The spectra of the as-implanted samples are characterized by a quadrupole split multiplet, showing that the Te ions come to rest at non-substitutional lattice sites. The laser annealing is shown to shift the implanted impurities towards substitutional positions. The efficiency of the laser annealing procedure is very similar for all lattices under study.

For x > 0.2, liquid SexTel-x alloys are semiconducting near the liquidus and have strongly temperature–dependent magnetic susceptibilities. We have studied the electronic paramagnetic centers by measuring their influence on the nuclear magnetic resonance shift and relaxation times of 77 Se and 125 Te in liquid Se .5Te.5. We find that the electronic centers are highly localized, their average hyperfine contact interaction with 125Te is three times that with 77Se, and the electronic spin correlation time is of order 1 psec at 350°C and decreases with rising T.

The motional correlation time, τc, in liquid Se and Se-rich Se-Te alloys has been investigated between 500 and 900°C using time differential perturbed angular correlations of y-rays from dilute 111Cd impurities. In all alloys we find τc ∝ exp (E0/kT) at low T where E0 = 0.36 eV. τC deviates from this relation at high T. At low T, τCis tentatively identified as the lifetime of a Cd to host molecule bond, and at high T as the average lifetime of bonds in the host molecule.

Two-phase tempering of martensitic Fe-9Ni steel serves to enhance the low temperature toughness and forms austenite precipitates in this material. Hyperfine field effects in Fe-Ni alloys were systematized so that tempering induced chemical composition changes in the martensite could be quantified by Mössbauer spectrometry. The kinetics of segregation of alloy elements from the martensite into the fresh austenite can be determined simultaneously with the amount of austenite which has formed.