Defects and Diffusion in Ceramics XII

Paper Title Page

Authors: Min Quan Kuang, Shao Yi Wu, Bo Tao Song, Li Li Li
Abstract: The EPR parameters and the local structure for Co2+ in ZnO are deduced from the perturbation formulas of these parameters for a 3d7 ion in a trigonally distorted tetrahedron. The ligand orbital and spin-orbit coupling contributions are taken into account uniformly from the cluster approach in view of the covalency of the system. The impurity V3+ is found not to locate exactly on the Zn2+ site but to experience a small displacement of 0.04 Ǻ away from the ligand triangle, along the C3 axis. The theoretical EPR parameters based upon the above impurity displacement are in good agreement with the observed values.
Authors: Saba Beg, Shehla Hafeez, Niyazi A.S. Al-Areqi
Abstract: Ceramic solid solutions Bi4MnxV2–xO11–(x/2)–δ in the composition range 0.07 ≤ x ≤ 0.30 were obtained by solid state synthesis. Structural investigations were carried out by using a combination of FT-IR and powder X-ray diffraction technique. Polymorphic transitions (β↔γ and γ′↔γ) were detected by DTA and variation in the Arrhenius plots of conductivity. The solid solutions with composition 0.07 ≤ x ≤ 0.17 are isostructural with the orthorhombic β-phase, and those with x ≤ 0.30 represent tetragonal γ-phase. With increasing Mn concentration, the conductivity of solid solutions increases from 3.684×10-6 (x = 0.07) to 2.467×10-5 (x = 0.17). AC impedance plots show that the conductivity is mainly due to the grain contribution which is evident in the enhanced short range diffusion of oxide ion vacancy in the grains with increasing temperature.
Authors: S.A. Aly
Abstract: The optical properties of cobalt oxide samples prepared by spray pyrolysis technique on glass substrates with different film thicknesses have been studied. The structural characteristics of the samples were investigated using X-ray diffraction. The optical properties of the prepared films were studied by transmittance and reflectance measurements, and the integrated transmittance (TVIS, and TNIR) and absorptance (AVIS and ANIR) in VIS and NIR regions was calculated and found to be affected by film thickness. The dependence of absorption coefficient on wave length was also reported. The energy gap was calculated and two energies have been observed at 2.15 and 1.5 eV suggesting that the deposited films are semi-conducting with allowed direct transitions.
Authors: M.Rizwan Malik, Zi Rong Tang, Tie Lin Shi, Lei Zhang, Shuang Xi, Dan Liu
Authors: Neha Sharma, Sunanda Sharda, Vineet Sharma, Pankaj Sharma
Abstract: Selenium-based glasses are attractive candidate materials because of their low transmission losses and other optical properties. In the present paper, samples of Ge19Se81-xSbx (x = 0, 4, 8, 12, 16, 17.2, 20) were prepared by using the melt-quench technique, and their X-ray diffraction spectra were studied. Some of the physical parameters were calculated theoretically. It was observed that the glass transition temperature increased up to x = 17.2 and then decreased whereas the theoretically calculated band-gap decreased with increasing Sb content.
Authors: Sunanda Sharda, Neha Sharma, Pankaj Sharma, Vineet Sharma
Abstract: Chalcogenide glasses are suitable for far-infrared and imaging applications. In the present study, Sb10Se90-xGex (x=0, 19, 21, 23, 25, 27) system has been chosen to study structural transformations via physical parameters. Bulk samples with x = 0, 19, 21, 23, 25 and 27 have been prepared using the melt-quenching technique. A theoretical study of the ternary glass system revealed that there was a significant change in the structural environment of the system due to rigidity percolation, which took place as Se was replaced by Ge, and hence resulted in changes in other physical parameters of the system.
Authors: Deepshikha Sharma, Saneel K. Thakur
Abstract: Alloys of (Se100-xBix)90Te10 (x =0, 0.5, 1, 1.5, 2, 2.5, 3 at.%) were prepared by using a conventional melt-quench technique. The samples under investigation were characterized using X-ray diffraction (XRD) and differential analysis (DTA) at a heating rate of 10K/min. It was found, from the XRD studies, that the alloys were amorphous in nature. The glass transition temperatures of the alloys were found to increase with increasing bismuth content. This increase in the glass transition temperature was explained on the basis of a chemically ordered network model.
Authors: M. Rizwan Malik, Tie Lin Shi, Zi Rong Tang, M. Haseeb
Abstract: Much of the recent ongoing advanced research into the quest for improved etching techniques has brought forth a broad concept for the fabrication of micro/nano-electromechanical systems (MEMS/NEMS) having high accuracy, precision, efficiency, compatibility and through-put of metallic- as well as carbon-composition structural phases. This in turn leads towards a thorough understanding of the sensing, trapping, separating, controlling, positioning, directing, concentrating and manipulating of micro-nano-sized particles - predominantly biological particles - in the emerging MEMS/NEMS technological field. This paper focuses its attention on the easiest means of wet-etching {100}-type silicon wafer surfaces by guiding the choice of [<100> or <010>] orientation (at 45° to the normal orientation). This anisotropic etching is performed in KOH solution. Here, consideration is not concerned to a large extent with process parameters as in anodic oxidation, an intensely doped boron etching stops and silicon wafer surface back-etching. The main concern of the present practical application route involves a passivating material (silicon dioxide, SiO2) and two masking stages (for a two-step etching process). As a example of this method, silicon cantilever beams having vertical edges are produced. It is concluded that the method presented will be helpful in the comprehensive study of resonators, pressure/temperature sensors, three-dimensional carbon micro-electrodes, actuators and accelerometers for bioparticle applications.
Authors: Kameshwar Kumar, Vimal Sharma, Pankaj Sharma, Nagesh Thakur
Authors: Saeid Khatami, Hamid Akrami, Ali Fattah
Abstract: In this work gas sensors based on PtSi Schottky diode using <100> n-type porous Si were designed, fabricated, and tested. These gas sensors detect polar gases (the gases with internal dipole moments) such as CO and non-polar gases (the gases without internal dipole moments) such as CO2. The operation of these Schottky diode sensors is carried out in breakdown region and shifts in their breakdown voltage in the presence of certain gases are mapped into the concentration of those gases in the environment. Fabrication of PtSi diode based gas sensors was reported earlier elsewhere. Our main objective in this work was to significantly reduce the breakdown voltage of these sensors hence making their use more economical. Such reduction was achieved through a series of systematic changes and optimization in the pore's geometries by careful study, analysis, and changes in the experimental conditions such as temperature, acid concentration, chemistry of the etching solution, and time.

Showing 1 to 10 of 17 Paper Titles