Volume 6, Issue 6
December 1984, pages 971-1092
pp 971-977 December 1984
A new method ofrf sputtering by which thin films of metals, semiconductors and insulators can be sputtered from their respective powders, has been successfully demonstrated. The films have been characterized for their surface and crystal structure using conventional methods ofsem andtem. All the films are amorphous with a relatively smooth surface topography. The relative merits and demerits of the technique have been briefly discussed.
pp 979-989 December 1984
Beta alumina solid electrolyte is a potential candidate in the fabrication of Na-S batteries. In the present study, it has been prepared in the form of discs by uniaxially as well as isostatically pressing and sintering in the temperature range 1585–1630°C, the highest sintered density of 3·25 g/cm3 has been achieved in the samples isostatically pressed and sintered at 1630°C. X-ray analysis of the samples shows formation ofβ″-phase. Microstructure of the sintered samples reveals some darker regions which are attributed to low soda content. Resistivity at 300°C measured by the two-probe method at a frequency of 1 MHz on samples having vacuum-deposited silver electrodes is 15 ohm-cm, which is slightly higher than the value of 5–13 ohm-cm reported in literature using molten sodium electrodes. The activation energy of conductivity is 0·24 eV which is comparable to the literature value of 0·24–0·35 eV.
pp 991-996 December 1984
Well-defined triangular etch pits are produced on etching (002) cleavages of lithium carbonate single crystals with 2% citric acid. On etching of cleavage face and matched face these pits nucleate at the intersection sites of dislocations with the cleavage face. On successive etching of a cleavage face, shallow irregular arrays of pits do not enlarge in size as compared to other isolated pits on the same face. These irregular arrays of pits have reasonable correspondence on an etched match face, suggesting they form at dislocation sites.
pp 997-1000 December 1984
The results obtained from etching experiments on the habit faces of NiMoO4·xH2O are described. Dilute solutions of chemical reagents such as HNO3, CH3COOH, NaOH, KOH are found to be the best etchants for revealing dislocation etch pits. The shape and nature of the etch pits are also described.
pp 1001-1007 December 1984
Results of measurement of elastic modulii on As-Sb-Se glasses are reported and their composition dependence discussed. The Young’s and the shear modulii lie in the range of 170–210 and 65–80 kb respectively. These values are typical of chalcogenide glasses. For (As, Sb)40Se60 glasses, the modulii increase monotonically with increasing Sb2Se3 content. The observed composition dependence of the modulii for the AsxSb15Se85 −x glasses is examined in terms of the chemically ordered structural units in the glasses.
pp 1009-1012 December 1984
The d.c. electrical conductivity of Na2O-ZnO-B2O3 glass system has been measured as a function of temperature in the range of 350–600°K. The conductivity data show that the activation energy of Na+ ions is dependent on ZnO concentration. The results have been discussed in the light of the cluster model of glasses.
pp 1013-1018 December 1984
Irradiation of 80° deposited Se-Ge films with band gap photons, 8 keV electrons and 50 keV He+ ions produces, primarily irreversible red shift of the absorption edge and major changes in doping and electrochemical adsorption processes. These changes have been attributed predominantly to the radiation-induced thickness and hence volume contraction resulting due to the physical collapse of the low density columnar microstructure of the obliquely deposited films. The farir and Urbach tail studies reveal an enhanced strength of electron-phonon coupling, in obliquely deposited films having a very porous columnar microstructure, compared to normally deposited films. It has been shown that this enhanced electron phonon coupling is conducive to large thickness contraction and associated changes. These changes have been used in reprographic and lithographic applications. A correlation has been established between the thickness contraction and lithographic parameters. The possibility of generating both positive and negative relief patterns on the same film by controlling the etching time has been demonstrated.
pp 1019-1027 December 1984
The oxidation of thin films of tin at room temperature in an atmosphere containing 10% H2S and 90% air has been studied by measuring the changes in resistance of thin films. Morphological studies have also been carried out using optical and scanning electron microscopes. Reaction kinetics change from logarithmic law at ordinary atmospheres to a power law in the presence of H2S. The basis of formation of sulphide along with the oxide is explained, the former growing on a lower layer and the latter on an upper layer.
pp 1029-1033 December 1984
The sheet resistivity of tin dioxide films deposited by electron-beam evaporation has been studied during annealing, both as a function of time and temperature. The annealing behaviour of SnO2 films under the above two different conditions is consistent. A qualitative interpretation has been given for the decrease and the minimum observed in the resistivity. The increase in resistivity has been confirmed by scanning-electron micrographs. The films were also characterized by x-ray diffractometry.
pp 1035-1039 December 1984
The temperature dependence of microhardness of mixed KCl-KBr crystals has been studied using the Kataoka and Yamada theory which considers plastic deformation and internal stress field due to elastic interactions in mixed crystals. The microhardness showed systematic variation with temperature in both the components and the mixed crystals and the probable reasons for this variation are indicated.
pp 1041-1046 December 1984
The glide dislocation-precipitate interaction in under-aged alloy is investigated by microscopy and low-temperature deformation techniques. Slip-line features of room temperature deformed samples were observed by optical microscopy. From tensile tests at various temperatures the variation of flow stress withT2/3 was established. Comparing the present results with those obtained on the peak-hardened condition of the same alloy it is concluded that moving dislocation shear through the small rod-shaped germanium precipitates.
pp 1047-1052 December 1984
A simple computer program is described to evaluate magnetic field distributions from complex Mössbauer spectra of magnetic alloys. The use of this program for test cases of Vitrovac 4040 amorphous sample and a simulated spectrum of two gaussian peaks is discussed.
pp 1053-1057 December 1984
The wavevector and temperature dependence of the spinwave linewidth in yttrium iron garnets has been studied for polycrystalline samples of average grain diameter 12·8µm and has been compared with the calculated relaxation times of basic three-magnon confluence and four-magnon scattering processes.
pp 1059-1062 December 1984
Mössbauer measurements have been performed on a number of metallic glasses. The temperature dependence of average hyperfine or internal magnetic fieldHeff(T) arises from long wavelength spin wave excitations in these glasses. Values ofB3/2 andC5/2 are in general much higher than those observed for crystalline ferromagnets indicating higher density of states for spin waves in amorphous ferromagnets.
pp 1063-1067 December 1984
Their spectra of a number of ferrites, MFe2O4, M(Mn, Fe, Co, Ni, Cu and Zn) have been studied at room temperature in the range 200–1000 cm−1. In all the cases the spectrum consists of four bands, two of which have strong absorption while the other two have weak absorption and often appear as shoulders on the main band. However up to 20% of the inverse ferrite, the shoulder in the low energy side appears as a band. In this paper we have analysed the origin of the above bands.
pp 1069-1074 December 1984
The exchange constants observed in the rare earth iron garnets, obtained from fitting magnetization and paramagnetic susceptibility as a function of temperature have been analysed in terms of Anderson’s theory of superexchange. The transfer integrals and covalency parameters have been obtained for various rare earth ions overlapping with oxygen.
pp 1075-1086 December 1984
A technique suitable for the measurement of electrical properties of films/sheets at microwave frequencies has been described. Groups of materials are identified for which the absence of any kind of electrodes in these microwave measurements can be utilised with advantage. Results are presented for a variety of materials such as metal films, superionic conductors, semiconductors and insulating polymers.
pp 1087-1091 December 1984
The surface modification of medical grade polyvinylchloride (pvc) from various sources with the ionic bonding of polyelectrolyte is investigated by exposing thepvc sheets to 1% zephiran chloride for 10 min and then to 50 mg% solution of polyelectrolyte for 10 min. Surface energy and platelet adhesion studies were carried out to demonstrate the suitability of our improved surface towards blood compatibility. Relative changes due toγ-irradiation are also discussed.
pp 1092-1092 December 1984 Erratum
Volume 42 | Issue 6
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