Bulk oxygen in a-silicon nitride and its effect on IR absorption

The existence of bulk oxygen in the lattice of silicon nitride is studied. In the study, silicon nitride, primarily ?-phase, is prepared by different methods and either powder or whiskers obtained, depending upon the method of preparation. On characterizing the samples, it is observed that they have almost identical XRD patterns, whereas there IR absorption spectra shows significant differences. This prompted another investigation and its results are presented

Bulk oxygen in alpha-silicon nitride and its effect on IR absorption

Results of an IR absorption characterization of alpha silicon nitride specimens prepared in the laboratory by several different procedures are presented. The results suggest the presence of bulk oxygen in the silicon nitride lattice. It is concluded that, although it is not necessary that alpha silicon nitride have bulk oxygen to stabilize its structure, it can accommodate a considerable amount of bulk oxygen without becoming oxynitride structurally

Preparation and nitridation of silicon whiskers

The preparation of high-purity silicon nitride powder (useful as high-temperature ceramic material) from silicon tetrachloride has been studied. Zinc was chosen for reduction to Si, which involved vapour reaction in a two-zone horizontal furnace. The silicon nitride whiskers formed were characterized by x-ray diffraction (XRD) and electron microscopy. The whiskers were very thin (approx 0.5 mu m, length gt; 1 cm) at low reaction temperature (950 deg C). In situ nitration with increased nitrogen flow was tried without success, although 0.1 mu m whisker thickness was obtained, and dry ammonia gas was then used for separate nitration at 1200-1300 deg C. XRD and infrared absorption data revealed alpha -Si sub 3 N sub 4 as the product (thickness 0.5, length approx 12 mu m). Such whisker-like particles with uniform aspect ratio may also be useful in ceramic composites

Development of Structural Ceramic Materials Silicon Nitride and Sialon

The activity on the development of the structural ceramic materials silicon nitride and sialons is highlighted. Special emphasis has been given to explore new methods and to develop low cost processes for the synthesis of these materials. An analysis of the oxygen content in various samples of a-silicon nitride has been made to show how the bulk oxygen content can vary depending on the method of preparation

Electronic And Thermal Properties Of Sn Added-Zn .Lsb3

3-Zn;Sb3 Is A Promising High Temperature Thermoelectric Materials With A High Power Factor Sea Where S Is The Thermopower And A Is Electrical Conductivity . It Is Found That The Properties Of (3-Zn4Sb3 Can Be Altered By Addition Of Sn. In This Paper The Electronic And Thermal Properties Of 13-Zn4Sb3 Are Given In Detail . Electrical Resistivity And Absolute Thermqpower Are Measured As A Function Of Temperature From Room Temperature To 300°C .Both Electrical Resistivity And Thermopower I Values Are Found To Increase With Addition Of Tin. It Is Observed Experimentally That At Lower Tin Concentrations (<I Weight %) Power Factor Remains Close To That Of 3-Zn4Sb3 And At Higher Concentration Of Sn Power Factor Decreases . Thermal Conductivity K, Of These Sn Added Zn.,+Sb3 Was Found To Be Lower Than That Of (3-Zn4Sb3 Showing A Noticeable Enhancement In ZT (=S 2at/K)At Low Concentration Of Tin

Preparation of Fibrous Silicon Carbide and its Evaluation

A PC based Resistograph has been designed and fabricated for studying13; the resistivity of metals, alloys and semiconductors as a function of13; temperature. This system has been installed at the Department of13; Physics, University of Mysore, Mysore

Synthesis of long/continuous fibres of silicon nitride

This report is on the work done on the development of fibres of silicon nitride during the period April 1998 - March 2000. The report also describes the effort made on the conversion of the fibrous silicon nitride into thin sheets. During attempts to infiltrate silicon carbide into these sheets by a chemical vapour deposition technique, it was observed that fibrous silicon carbide is formed under certain conditions. This had led to a process for the preparation of fibrous silicon carbid

Synthesis of Silicon Nitride and Related Materials

Work carried out in the laboratory on the synthesis of a-silicon nitride powder and whiskers, B -silicon nitride powder, and -sialon powder is given in the report. Studies on understanding the importance of oxygen in stabilising the a-silicon nitride structure as well as those on the synthesis of silicon whisker are13; also reported

Synthesis and crystal growth of IR detector materials

This report pertains to the synthesis, crystal growth and characterisation of the infrared detector materials - mercury cadmium telluride (MCT) and lead tin telluride (LTD in a composition suitable for use in the 8-14 mew wavelength region. The procedures adopted for the crystal growth of MCT and LTT and the methods used for characterising the crystals for homogeneity of composition, dislocation density, energy band gap, intrinsic carrier concentration and carrier mobility are described. The results obtained from these studies are discussed. These studies indicate the suitability of these cystals for detector applications