Yuanfu Hsia

Mössbauer studies of57Fe in high-Tc superconductors YBa2 (Cu1−xFex)3O7

Various phenomena induced by iron cation substitution for copper in high-Tc superconductor are discussed. Fe cations are substituted for both Cu(1) and Cu(2) sites, but the substitution is preferentially taking place on Cu(1) chain sites atx<3%. The Fe cations at Cu(1) chain sites exhibit anisotropic vibration. Three different types of oxygen coordinations of Fe(1) cations are identified by the point-charge model. The calculation indicates that Fe3+ are present in tetrahedral, pyramidal, and distorted octahedral coordinations.

Investigation of some anomalous hemoglobins

We have studied some anomalous hemoglobins by Mössbauer spectroscopy. We found that there is a correspondence between the physical conditions of the respective patients and the additional components of the Mössbauer spectra found for their hemoglobins.

Lamb-Mössbauer factor in the spin crossover compound Fe(tpa)(NCS)2

The Lamb-Mössbauer factor in spin crossover compounds has been the subject of controversial discussions in the literature. For several compounds, a significantly larger Lamb-Mössbauer factor for the complex molecules in the low-spin (fls) than in the high-spin (fhs) state has been reported, while for compounds studied in our laboratory such differences could not be observed. We prepared the compound Fe(tpa)(NCS)2, thef factors of which were reported to be very different. We could not prove thef factors of this compound to be different. The implications of a different structural phase of compound prepared by us are discussed.

Studies of archaeological problems by Mössbauer spectroscopy

The recent developments and achievements of the application of Mössbauer spectroscopy to archaeological problems are reviewed. The relevances of Mössbauer spectroscopy in studies of provenance, manufacturing technology and age dating of ancient pottery, as well as the ancient bronzes are discussed.

The surfactant influence on the surface magnetic properties of Fe3O4 microcrystals

Mössbauer measurements, electron microscopy and infrared spectroscopy, have been used for investigating the Fe3O4 microcrystals coated with different surfactants. The experimental results show that the surface condition of the system changes and the anisotropy energy constantK of Fe3O4 microcrystals increases effectively when the surfactants being added. The spin pinning effect on a sample surface was observed and the pinning depth and the pinning direction were estimated. Besides, it has been shown that the anisotropy energy constantK of the coated Fe3O4 has an abrupt change nearbyTv.

Fe-57 Mössbauer effect studies of some ancient Chinese pottery from xudun

Abstract18 Sherds (4500 B.C.–4000 B.C.) unearthed from different archaeological layers at the same place were studied by Mössbauer spectroscopy. The original firing atmosphere can be deduced from the ratio of the Fe2+ to Fe3+. By comparing the Mössbauer parameters of the original and the refired sherds, we can assess the original firing temperatures.

Influence of solvent on the superparamagnetic relaxation of nanocrystalline Fe3O4 in ferrofluids

Mössbauer spectra for 5 nm Fe3O4 nanocrystallites coated with different surfactants were measured and show a significant influence on superparamagnetic relaxation with and without the solvent in ferrofluids.

A Mössbauer investigation of SnO2 films with preferred orientation of crystallites

The textured SnO2 films with different thickness in the range of 600–11200Å prepared by chemical vapour deposition (CVD) have been characterized by using conversion electron Mössbauer spectroscopy (CEMS) couping with X-ray diffraction (XRD) and Auger electron spectroscopy (AES). The evidence for the existence of an interaction between SnO2 and glass substrate with the formation of a interface layer about 200Å thick has been discussed. SnO2 existing in polycrystalline state with preferred crystal face orientation is found as long as the SnO2 films are thick than 1800Å.

Mössbauer study of iodine-doped polythiophene and poly(3-methylthiophene)

The129I Mössbauer study applied to the iodine-doped polythiophene and poly(3-methylthiophene) films revealed that the iodine consists of pentaiodide, triiodide, and/or I2 molecules. The abundance ratios of these iodine species vary with the doping level.

A Mössbauer study of an ancient pottery figure (Western-Han dynasty)

The grey pottery figure manufactured in the Western-Han Dynasty (175-118 B.C.) and the clay gathered from the same site of Beidongshan in Xuzhou have been studied by X-ray Diffraction(XRD). X-ray Fluorescence (XRF), and Mössbauer spectroscopy. They were simultaneously fired under the same conditions in different atmospheres at various temperature up to 1100°C. This study deals with the original firing atmosphere, original firing temperature and its provenance. The information mentioned above can be inferred from the method of the refiring pottery and the firing clay. The results of the original firing temperature deduced from both of them are in goodself agreement. It is found that the values of the Mössbauer parameters for the unrefired pottery figure are approximately the same as those for the clay fired at 950°C for five hours in a reduced atmosphere. The XRF analysis confirmed the locality of this pottery figure.