Physical Properties of Porous Pure and Zr/Sn-Doped Nanocrystalline BaTiO3 Ceramics

Polycrystalline BaTiO3 and Ba(Ti0.96SnxZr0.04-x)O3 ceramics (x = 0.02-0.04) were prepared by a combination of solid-state and mechanochemical process and characterized at room temperature by X-ray diffraction for phase composition. Their crystal structures were found to be of the cubic and tetragonal symmetries, respectively. The grain size and porosity which were determined using Field Emission Scanning Electron Microscope (FESEM) and densitometer, respectively showed decrease and increase of relative density respectively, with increase in doping concentration. The variations of dielectric constant and loss with frequency and temperature show a maximum dielectric constant of 1660 at room temperature for Ba(Ti0.96Sn0.03Zr0.01)O3. The remnant polarization (Pr) and coercive field (Ec) of BT were found to be 581.73 V/cm and 0.27 μC/cm2. Increase in Sn content led to an increase in Pr of 0.58, 3.07, 3.73 C/cm2, and Ec of 1766.8, 2855.7, 2661.1 V/cm, respectively and are expected to lead to a significant reduction in the thickness of the multilayer ceramic capacitors. Impedance spectroscopy of polycrystalline Ba (Ti0.96Sn0.02Zr0.02) O3 in a wide frequency and temperature range showed Nyquist plots with presence of grain and grain boundary at 400°C and a negative temperature coefficient of resistance (NTCR) for Ba(Ti0.96Sn0.02Zr0.02)O3. The dielectric relaxation showed a non-Debye character

On The Effect of Electron-Hole Recombination in Disordered GaAs-Aa1-xALAs Multi-quantum Well Structure

The disordered electron-hole recombination in multi-quantum well was investigated using analytical method based on the rate equations. The results show extreme broad distribution of the recombination time which depends exponentially on the distances between the recombining excitons. The energies at each localised state shows an energy splitting between the electronic ground state and the first excited state of 0.0038eV

CAPM or APT? A comparison of two asset pricing models for Malaysia

This study uses monthly return data on 213 stocks listed on the main board of Kuala Lumpur Stock Exchange, Malaysia for the period September 1988 to June 1997 to compare two frequently cited asset pricing models: the capital asset pricing model, CAPM and the arbitrage pricing theory, APT. A comparison was performed along the lines of Chen (1983) and the results showed the APT to perform better than the CAPM in explaining the variations in cross section of returns. The implication for investors is that the market index is but one of several sources of risk , which should be taken into account in any decision governing investment in the stock market

Behaviour of stock returns in the KLSE: A test of the random walk hypothesis

A sample of 224 companies listed in the Kuala Lumpur Stock Exchange was taken for the period 1991-96. The serial correlations tests of varying lags and the runs tests were employed to test for the random walk theory. The bulk of the results tilts towards the rejection of non-randomness, lending weight to the argument that the stock market has no memory, and casting doubt upon the usefulness of technical analysis

Antimicrobial profiles of Salmonella species isolated from ruminants slaughtered at the two major abattoirs in Ilorin, Nigeria

Background: Foodborne illness due to the genus Salmonella is one of the major challenges affecting public health worldwide and a threat to socioeconomic activities especially in the developing countries. The present study was carried out to determine the isolation rate and antimicrobial susceptibility profiles of Salmonella species from ruminants slaughtered for human consumption at the two major abattoirs in Ilorin, Kwara State. Methods: Between November, 2019 and February, 2020, a total 500 samples were collected from the two major abattoirs in Ilorin metropolis (cattle, n = 240; goat, n = 260). Salmonella species were isolated and identified using standard bacteriological techniques. The isolates were subjected antimicrobial susceptibility test using Kirby Bauer disk diffusion assay. Results: 20 (4 %) Salmonella isolates were obtained, there was no significant statistical difference between the isolation rates from cattle (3.75 %) and the small ruminant (4.23 %). Varying degree of resistance patterns were obtained with high proportion of the isolates (> 60 %) displaying resistance to penicillin and cephalosporin tested while low resistant phenotypes (5 %) were observed against quinolones. The isolates were pan-susceptible to gentamicin. Conclusion: The study documented multidrug resistant Salmonella isolates from ruminants slaughtered for human consumption. It is recommended that further studies to characterize the isolates will assist in recommending the appropriate control strategies to prevent the transmission of resistant Salmonella strains to human via food chain

Knowledge, attitudes, and practice of exclusive breast feeding amongst mothers attending postnatal clinic in Tswaing sub-district, North West Province

M.Fam.Med., Faculty of Health Sciences, University of the Witwatersrand, 201

Electrical and Dielectric Characterization of Na 0.5 Li 0.5 Zr 2 (PO 4 ) 3

Abstract Na 0.5 Li 0.5 Zr 2 (PO 4 ) 3 has been synthesized by solid state reaction and characterized by thermogravimetry/ differential thermal analyses (TGA/DTA) in the temperature range 300 -1573 K. X-ray diffraction measurements have been carried out to determine the phase of the composition and scanning electron microscopy (SEM) for microstructure evaluation. Impedance spectroscopy at different temperatures (310 -600 K) and frequencies (300 kHz -1 GHz) have been carried out and the dielectric relaxation behaviour was determined under the same conditions. A dc conductivity maximum value of 0.25 S/m at 580 K was observed. However, the mixed alkali effect was not observed. The material exhibited relaxation behaviour with a peak in the dielectric permitivity ' at 469 K. There were no structural transformations observed

Sintering behavior, ac conductivity and dielectric relaxation of Li1.3Ti1.7Al0.3(PO4)3 NASICON compound

The phenomenon of relaxation in dielectric materials is described as one of the powerful tools to determine the behavior and properties of ion transport. The kinetics of ionic species and dipole in solid-state electrolyte are dependent on frequency, temperature, and dielectric relaxation. Li1+xTi2−xAlx(PO4)3 conducting solid state electrolyte with x = 0.3 was synthesized via conventional solid state technique using the raw materials Li2CO3, TiO2, Al2O3, and NH4H2PO4 as starting materials. TGA/DTG and X-ray diffraction measurements were carried out to study the thermal behavior and phases of the composition. It was observed from the TGA/DTA curves that there is no mass loss above 500 °C. The XRD peaks were observed to start appearing at 500 °C which corresponds to small peaks in TGA. It was also pointed out that at increasing sintering temperatures from 700 °C to 1000 °C the number of phases drastically decreased which is attributed to the complete chemical reaction. Temperature and frequency dependence of dielectric relaxation and electric modulus of the compounds were investigated at temperatures 30–230 °C and at frequencies of 40 kHz–1 MHz. The findings showed that the dielectric relaxation peaks shift to higher temperature as frequency increases and the change in ac conductivity with frequency is in agreement with Jonscher’s power law. Keywords: Sintering behavior, Dielectric permittivity, Universal power law, Electric modulu

Structural and microstructural study of gamma ray-irradiated co-doped barium titanate (Ba0.88Ca0.12Ti0.975Sn0.025O3)

Barium calcium stannate titanate (Ba0.88Ca0.12Ti0.975Sn0.025O3) ceramics, synthesized by solid state reaction method and sintered at 1100 °C/3 h, were exposed to gamma radiation dose of up to 1 kGy using a Cs-137 irradiation source at a dose rate of 100.46 Gv/h. Structural analysis of the ceramics indicated a tetragonal perovskite crystalline structure for both pristine and irradiated ceramics with a minor secondary phase. However, slight changes of the lattice parameters and average crystallite size were observed for the irradiated samples. The lattice aspect ratio of the tetragonal phase (c/a) for the pristine ceramics was 1.0022 which decreased by 0.22% at maximum irradiation dose. Irradiation also causes some microstructural changes and slight decrease in grain size. Energy dispersive spectroscopic investigation of the Ba0.88Ca0.12Ti0.975Sn0.025O3 showed small variation in its chemical composition as gamma radiation dose is increased