Showing papers by "Solid State Physics Laboratory published in 1970"

Variation of lattice parameter with temperature and thermal expansion of the compound Cu2SnSe3

Abstract: The temperature variation of the lattice parameter of the compound Cu2SnSe3 has been studied in the temperature range 30 to 600°C by X-ray diffraction methods. The linear coefficient of thermal expansion at room temperature (30°C) is 20.4 × 10−6 deg−1 and it is found to decrease with increasing temperature. Die Temperaturanderung des Gitterparameters der Verbindung Cu2SnSe3 wurde im Temperaturbereich 30 bis 600°C durch Rontgenstrahlenbeugungsmethoden untersucht. Der lineare Koeffizient der thermischen Ausdehnung bei Zimmertemperatur (30°C) betragt 20,4 × 10−6 grd−1 und nimmt mit steigender Temperatur ab.

Metallic particles in alkaline earth fluorides

Abstract: Coagulation of colour centres in additively coloured alkaline earth fluoride crystals at high temperatures leads to the formation of metallic precipitates in well-developed crystallites. The maximum obtainable sizes are approximately 10 μm. Evidence is found that the calcium and strontium precipitates in CaF2 and SrF2, formed below 850°C have the f.c.c. lattice structure, while above 1000°C the b.c.c. structure is favoured. For barium precipitates formed at temperatures below 850°C the crystal structure has been found to be b.c.c. The Ba-particles formed above 1000°C appear to be precipitated in the molten phase. Die Koagulation von Farbzentren in additiv verfarbten Erdalkalifluorid-Kristallen gibt Anlas zur Bildung metallischer Prazipitate, wobei gut ausgebildete Kristallite entstehen. Die maximale Grose dieser Kristallite betragt ungefahr 10 μm. Es wird gezeigt, das die Kalzium- und Strontiumprazipitate, die unter 850°C entstehen, eine kubisch-flachenzentrierte Struktur besitzen, wahrend uber 1000°C die kubisch-raumzentrierte Struktur bevorzugt wird. Beim Barium wird unter 850°C die raumzentrierte Struktur gefunden; uber 1000°C scheinen die Bariumteilchen sich aus einer flussigen Phase abzuscheiden.

Theory of F-Centres in Alkaline Earth Fluorides

Abstract: F-centres in alkaline earth fluorides have been investigated by means of optical and ESR experiments. From these results we can obtain information about the charge distribution, which appears to deviate from that observed in the alkali halides. We have found some evidence that LCAO-type wave functions give a better description of the physical properties of F-centres in alkaline earth fluorides than the conventional central wave functions, which were quite successful in describing the F-electron in the alkali halides. Some new relations between the optical transition energy and the hfs constants and the radius of the monovalent cations surrounding the vacancy are given. Es wurden F-Zentren in Erdalkalifluoriden mittels optischer und ESR-Methoden untersucht. Die Ergebnisse der Messungen erlauben, uber die Ladungsverteilung in den Zentren Schlusse zu ziehen, die sich als verschieden von denen in den Alkalihalogeniden herausstellen. Es last sich zeigen, das Wellenfunktionen vom LCAO-Typ eine bessere Beschreibung der physikalischen Eigenschaften der F-Zentren in Erdalkalifluoriden geben als die bei den Alkalihalogeniden so erfolgreichen konventionellen Zentralwellenfunktionen. Einige neue Beziehungen zwischen den optischen Ubergangsenergien und den HFS-Konstanten und dem Radius der monovalenten Kationen, die die Leerstelle umgeben, werden angegeben.

Some physical investigations on photovoltaic effects in Cu2S-CdS heterojunctions

Abstract: The photovoltaic effect in Cu2s-CdS heterojunction has been the subject of study by a large number of investigators. Proper heat treatment of the junction plays crucial role in optimizing the performance of the heterojunction. In this paper, after a brief review of the work on Cu2S-CdS heterojunctions, the profile of copper in CdS as a function of heat treatment will be discussed. The diffusion of copper from Cu2S into CdS has been studied at various temperatures, by radioactive tracer methods. This has a bearing on the spectral response of the Cu2S-CdS cells as a function of heat treatment.

Electrical conductivity of thallous sulphate crystals

Abstract: Electrical conductivity of Thallus sulphate single crystals grown from melt is measured in the temperature range 100°-500°C using d. c. electrometer circuitary. The plot of Log [sgrave] versus (103/T°K) consists of two linear parts with slopes giving an activation energy of 0. 5 eV for the region 100°-410 °C and 1. 1 eV for the region 410°-500 °C. A tentative identification of the low and high temperature conduction regions as extrinsic and intrinsic respectively. leads to a value of 0. 5 eV for the enerm of migration of the mobile defect and 1. 2 eV for the energy of formation of a defect pair.

Preparation and electrical properties of InSe

Abstract: Single crystals of Indium Selenide are prepared by vapour growth technique as it is difficult to prepare large single crystals by vertical Bridgman technique. The effect of stochiometric changes an...