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The optical band-gap energy (Eg) is an important feature of semiconductors which determines their applications in optoelectronics. Therefore, it is necessary to investigate the electronic states of ceramic ZnO and the effect of doped impurities under different processing conditions. Eg of the ceramic ZnO + xBi2O3 + xTiO2, where x = 0.5 mol%, was determined using a UV-Vis spectrophotometer attached to a Reflectance Spectroscopy Accessory for powdered samples. The samples was prepared using the solid-state route and sintered at temperatures from 1140 to 1260 °C for 45 and 90 minutes. Eg was observed to decrease with an increase of sintering temperature. XRD analysis indicated hexagonal ZnO and few small peaks of intergranular layers of secondary phases. The relative density of the sintered ceramics decreased and the average grain size increased with the increase of sintering temperature.

Cobalt–nickel ferrite (Co0.5Ni0.5Fe2 O4) were prepared using a high energy milling and sintering. The starting raw materials of NiO, Co3O4 and Fe2O3 were subjected to 12 hr milling using a Spex8000D mixer/mill. The resulting material was molded into samples of toroidal/disc shape and subsequently sintered at various temperatures from 600 to 1000° C, at 100° C interval. The effect of sintering temperature on microstructure, saturation magnetization (Ms), and coercivity (Hc) was reported. The frequency dependence of the magnetic and dielectric properties such as permittivity, loss tangent, permeability and loss factor were investigated in the frequency range of 10 MHz–1.8 GHz. The results show that the real part of the permittivity at individual temperatures was constant within the measured frequency, while the loss tangent values decreased gradually with increasing frequency. The real permeability on the other hand remained fairly constant over certain frequency (around 1.0 GHz), and thereafter increases towards saturation thereby showing a good potential in the microwave frequencies region.

Drilling as a novel Surface Sever Plastic Deformation method (SSPD) has been applied to commercial CK60 steel plate to create a Nano Crystalline (NC) structured layer. In present study, the CK60 steel plate has been quenched in room temperature water from 950 °C (1 Hr) and tempered in 350°C for one hour. Drilling has been done with use of Ti-Carbide coated drilling bit under 10, 15 and 20 m/min speeds. The microstructure of the samples was studied by light microscope and high resolution SEM. The formation of NC layer having grain size in the order of 50nm was confirmed by the SEM observation and applying Hall-Pitch formula on the samples drilled with 15 m/min speed. The created fine grain zone is separated from base metal structure and clear boundary with 1 to 10 microns thickness where the drilling speed changes from 15 to 20 m/min. The microhardness test result illustrates that the hardness of surface NC layer increases almost more than twice when compared with coarse grain structure of base metal.

The optical band-gap energy (Eg) is an important feature of semiconductors which determines their applications in optoelectronics. So, it is necessary to investigate the electronic states of ceramic ZnO and effect of doped impurities at different processing conditions. Eg of the ceramic ZnO + xBi2O3 + xTiO2 where x = 0.5 mol%, was determined using UV-Vis spectrophotometer. The samples was prepared using solid-state route and sintered at the sintering temperatures from 1140 to 1260°C for 45 min in open air. Eg was decreased with increase of sintering temperature. XRD analysis indicates that there is hexagonal ZnO and few small peaks of inter granular layers of secondary phases, namely, Bi4Ti3O12 and Zn2Ti3O8. The relative density of the sintered ceramics decreased and the average grain size increased with the increase of sintering temperature. The variation of sintering temperatures and XRD findings are correlated with the UV-Vis spectrophotometer results of ZnO doped with 0.5 mol% of Bi2O3 and TiO2 due to the formation of interface states at all sintering temperatures.

The polycrystalline Ni–Zn ferrite powder with the chemical formula Ni0.8Zn0.2Fe2O4 has been synthesized using co-precipitation route. The toroidal and pellet form samples were sintered at various temperatures from 700 to 1300 °C/5 h in steps of 200 °C. The structures of samples were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and the energy dispersive X-ray spectroscopy (EDXS). The magnetic and dielectric measurements were carried out using a vibrating sample magnetometer (VSM) and the impedance analyzer, respectively. The highest density of 4.48 g cm−3 was obtained for the sample sintered at 1300 °C. It was found that the initial permeability increased from 4 to 17 and the RLF was in the order of 10−3 to 10−4 in the frequency range of 1.0 MHz to 1.0 GHz. The dielectric constant and dielectric loss were lower compared to the reported values for conventional solid state technique. The electrical resistivity is in the order of 108 Ω cm. Therefore, low relative loss factor and high resistivity make these ferrites particularly useful as inductor and transformer materials for high frequency applications.

Problem statement: In the last decade, the studies and investigation on polymer-based composites have drawn significant attention owing to improvement in their mechanical, thermal, electrical, optical and pharmaceutical properties as compared with pure polymer. Approach: Different compositions of Ni0.2Zn0.8Fe2O4 (NZF) and Polypropylene (PP) can alter the useful properties of polymer-based composites. Hence, the determination toward significant percentage of NZF added into PP can improve the dielectric properties of the composites. NZF was prepared using conventional solid-state method and composites of isotactic PP filled with NZF were fabricated. The dielectric properties of the composite were investigated using Agilent 4284A Precision LCR meter. Results: The results indicated that with increasing ratio of wt% NZF, the dielectric constant and dielectric loss of the composite increases. The composition of 30 wt% NZF gave the highest value of the dielectric constant in the frequency range of 100 Hz-10 kHz at room temperature. Conclusion: The incorporation of ceramic filler improved the dielectric constant and increase the dielectric loss of the composite correspondingly increases its potential use as an absorbing material for electromagnetic waves.

Nanosized cobalt ferrite spinel particles have been prepared by using mechanically alloyed nanoparticles. The effects of various preparation parameters on the crystallite size of cobalt ferrite which includes milling time; ball-to powder weight ratio (BPR) and sintering temperature, were studied using X-ray diffractometer (XRD). Scherrer's equation was used to study the crystallite size evolution of the as-prepared materials. The results of the as-milled sample revealed that both milling time and BPR plays a role in determining the crystallite size of the milled powder. However, where sintering is involved, the sintering temperature results in grain growth, and thus plays a dominant role in determining the final crystallite size of the samples sintered at higher temperature (above 900 °C). From the vibrating-sample magnetometer (VSM) measurement it was observed that the coercivity of the as-milled samples without sintering is almost negligible, which is a type characteristic of superparamagnetic material. However, for the sintered samples, the saturation increases while coercivity decreases with increases sintering temperature.

Nickel-zinc ferrite (Ni0.2Zn0.8Fe2O4) was prepared using conventional solid-state method. It acts as a filler with polypropylene as the matrix. The samples were characterized by XRD and dielectric measurement was done using Agilent 4291B Impedance/Material Analyzer. It was observed that the composition of 30% doped nickel-zinc ferrite (Ni0.2Zn0.8Fe2O4) gives the highest value of the dielectric constant in the frequency range of 1 MHz to 1.5 GHz at room temperature.

Crystalline, magnetic, cobalt ferrite nanoparticles were synthesized from an aqueous solution containing metal nitrates and polyvinyl pyrrolidone (PVP) as a capping agent by a thermal treatment followed by calcination at various temperatures from 673 to 923?K. The structural characteristics of the calcined samples were determined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and transmission electron microscopy (TEM). A completed crystallization occurred at 823 and 923?K, as shown by the absence of organic absorption bands in the FT-IR spectrum. Magnetization measurements were obtained at room temperature by using a vibrating sample magnetometer (VSM), which showed that the calcined samples exhibited typical magnetic behaviors.

The binary glass system of (TeO2)x (B2O3)1-x with x= 60 to 80 mol% were synthesized by rapid quenching method. Longitudinal and shear ultrasonic velocity were measured at room temperature and at 5 MHz frequency. Elastic properties, Poisson’s ratio and micro hardness have been calculated from the measured density and ultrasonic velocity at room temperature. The transition temperature was also measured. The experimental results indicate that the elastic moduli of the binary glass system increase with TeO2 content as the glass system become more rigid due to the mix former effect.

The magnetic and physical properties of ferrites are very sensitive to microstructure, which in turn critically depends on the manufacturing process. In this study, nickel zinc ferrite powder with composition Ni0.8Zn0.2Fe2O4 has been prepared via conventional ceramic processing and co-precipitation methods. The toroidal and pellet form samples were sintered at various temperatures such as 1100, 1200 and 1300 °C. The microstructure, magnetic and dielectric properties of both samples were studied. The X-ray diffraction patterns confirm the formation of single-phase cubic spinel structure for the co-precipitation technique after sintering. The microstructure studies of Ni0.8Zn0.2Fe2O4 show the grain size increases and the porosity decreases with temperature for both methods. The controlled permeability with small loss and wide operational frequency range are found in the co-precipitation samples. Dielectric constants decrease with increase of frequency and increase with sintering temperature in both methods. Consequently, the homogenous microstructure with the low-loss high-performance of nickel zinc ferrite has been discovered by means of co-precipitation method.

Homogeneous (Fe2O3)x (TeO2)1-x were synthesis using melt- quenching technique for x= 0.1-0.3 in the interval of 0.05. The binary glasses were dark brown in colour. The amorphous structure of glasses was confirmed by the X-ray diffraction spectrum. The physical properties such as density and molar volume have been determined in room temperature and were found decrease with Fe2O3 contents increase. From the vibrating-sample magnetometer (VSM) measurement it was observed that that magnetization of glass increase almost linearly with applied fields and shows paramagnetic materials behavior.

Co0.4Ni0.3Zn0.3Fe2O4 ferrites material with the crystallite size in the size range 10-50 nm was prepared using mechanical alloying and sintering. The structure and morphology of samples were studies. The initial permeability (μ') and permittivity (ß') has been studied as the functions of frequency and the sintering temperatures sintering temperature using a network analyzer from 10 MHz to 1.8 GHz. X-ray diffraction confirmed the formation of spinel structure and a scanning electron micrograph was used to analyze the grain size distribution of ferrite. The permeability spectra of the resulting ferrite samples shows increasing values with the increasing sintering temperature, this is attributed to the grain growth as a result of the sintering process. Permittivity ß' also increases with increasing average grain size, which may be ascribed to the increase in an increase in the Fe2+ concentration formed at elevated sintering temperature.

Problem statement: This study involved an investigation to ascertain the diffusion of NiO and ZnO into the tetrahedral and octahedral sites using mechanical alloying method. The effect of mechanical alloying towards particle size was also reported. Approach: NiO, ZnO and Fe2O3 precursors were mechanically alloyed to synthesis ultrafine powders of Ni0.5Zn0.5Fe2O4. Various milling times were employed to study the effect of milling time on the materials. The ultrafine powder was sampled after each milling time and further characterized using XRD to investigate the phases of the powder and the crystallite size, SEM for the morphology and TEM for particle size investigation. Results: The XRD spectra indicated the precursors reacted during milling with the diffusion of ZnO and followed by NiO into their respective crystallographic sites. SEM micrographs showed the agglomeration of powders due to high energy milling and TEM images proved the particles of the materials were of nanosize. Conclusion: It was concluded that samples prepared using mechanical alloying technique appear to be a potential method for large production due to the possible reduction of cost and also reduction of particle size against milling time.

This research was designed to form better dielectric composite material using one steady state dielectric (mullite) with a good dielectric material (strontium titanate). Distinct dielectric composites were successfully produced using locally sourced kaolinite clay. The samples were made using mullite as the base matrix and strontium titanate (ST) added at varying ratios. Strontium titanate was synthesized via solid-state reaction using strontium carbonate and rutile titanium (IV) oxide sintered at 1300°C. Local white kaolinite was used to fuse the strontium titanate material at varying weight ratios. The powders were dry-mixed and made into pellets for calcination at 1000°C. XRD and SEM characterizations were made. The dielectric measurements were carried out using the HP 4192A LF Impedance Analyzer dielectric setup in the frequency range of 10 Hz to 1 MHz. Three samples were prepared, namely ST 60%, ST 70% and ST 80%. The dielectric measurements were carried out in a controlled LT furnace at 30°C - 400°C. Measurements showed distinct varying interfacial encapsulation and dipolar relaxation for all composite samples.

Nanoparticle-size d cobalt ferrites (CoFe2O4) were prepared via high energy mechanical alloying using a Spex8000D mixer/mill and heat treatment. The starting raw materials Co3O4 and Fe3O4 were milled for 12 hours in air, molded into samples of toroidal and disc shape and subs equently sintered at various temperatures from 600 to 1000 °C. The effect of sintering temperature on microstructure, magnetic and dielectric properties like saturation magnetic moment (Ms), coercivity (Hc), retentivity (Mr) permittivity and permeability were investigated in the frequency range 10 MHz to 1.8 GHz. The results show that single phase cobalt ferrites could not be formed during milling alone, however it formed at 600 °C. The crystallization of the cobalt ferrites was seen to increase strongly up to 1000°C. Further observed was that the crystallite size increased with the increasing sintering temperature. A high coercivity of up to 1982 Oe and a magnetization of 47 emu/g were obtained after an optimized heat treatment at 800 and 900°C respectively.

Strontium Titanate, SrTiO3 samples were prepared using the conventional solid state reaction method. SrTiO3 samples were sintered at 1100°C, 1200°C, and 1300°C. XRD was used to determine the crystalline structure of the samples. The AFM showed the grain size was significantly increased with an increase in sintering temperatures. The dielectric properties of the sample were measured using Agilent 4291B Impedance/material Analyzer in the sub-microwave region in the frequency range 1 MHz to 1.5 GHz at room temperature. The dielectric constant and the average grain size were found to be the highest for the SrTiO3 sample sintered at 1200°C. Hence, greatest dielectric polarization occurred in the sample with the largest grain size.

Photopyroelectric spectroscopy is used to study the energy band-gap of the ceramic (ZnO 0.25 Bi2O3 +0.25 TiO2 + x MnO2), x = 0 - 1.3 mol%, sintered at isothermal temperature 1190 and 1270°C for 2 hours in air. The wavelength of incident light, modulated at 9 Hz, is kept in the range of 300 to 800 nm and the photopyroelectric spectrum with reference to the doping level is discussed. The energy band-gap is estimated from the plot (phv)2 vs hv and is 2.80 eV for the samples without MnO2 at both sintering temperatures. It decreases to 2.08 eV with a further increase of MnO2. The phase constitution is determined by XRD analysis. Microstructure and compositional analysis of the selected areas are analyzed using SEM and EDX. The maximum relative density, 91.4 %, and the grain size, 47 µm, were observed in this ceramics combination.

CaCu3Ti4O12 (CCTO) was prepared by a conventional solid state reaction method. CCTO sample was pre-sintered at 900°C for 10 hours and sintered at 1075°C for 12 hours. The dielectric properties of the sample were measured using HP 4192A LF Impedance Analyzer. The complex permittivity was measured within the frequency range from 10 Hz to 106 Hz and the temperature ranging from 30°C to 400°C. The results showed that the dielectric constant and dielectric loss factor of the sample are frequency dependent and temperature dependent. CCTO sample exhibits a high dielectric constant which is around 105. Dielectric constant increases with decreasing frequency due to interfacial polarization. This could be explained by the Maxwell- Wagner effect.

This research was designed to form better dielectric composite material using one steady state dielectric with a good dielectric material. Distinct dielectric composites were successfully produced using locally sourced kaolinite clay. The samples were made using kaolinite as the base matrix and Barium Titanate (BT) added at varying ratios. Barium Titanate was synthesized via solid-state reaction using Barium Carbonate and rutile Titanium (IV) Oxide sintered at 1300°C. Local white kaolinite was used as the matrix at varying weight ratios. The powders were dry-mixed and made into pellets for calcination at 1000°C. The dielectric measurements were carried out using HP 4291B Impedance Analyzer dielectric setup. Three samples were prepared, namely 50%BT, 60%BT, and 70%BT. The dielectric measurements were carried out in an LT furnace at temperatures 30°C - 400°C with frequencies ranging from 10 Hz to 1 MHz. Measurements showed varying ionic relaxation for all samples.

Photopyroelectric (PPE) spectroscopy is a useful tool for examining optical properties in semiconductor materials. The ceramic (ZnO - xTiO₂) was sintered at 1270⁰C for 1 and 3 hours to investigate the variations of energy band-gap with respect to mol % of dopant TiO₂. The X-ray diffractrometry shows that the crystal structure of ZnO doped at low level remains to be of hexagonal type but has developed second phase, Zn₂TiO₄, at high level. Microstructure and compositional analysis of the selected areas are analyzed using SEM and EDAX. The maximum grain size obtained were 26.8, 52.4 µm at 0.4 mol % of TiO₂ for 1 and 3 hours sintering time, respectively. The band-gap determined from the photopyroelectric spectrum has the value of 2.82 ± 0.01 eV for samples sintered for 1 and 3 hours at the doping level of 0.4 mol % of TiO₂ and decreases with the increase of TiO₂.

The dielectric properties of Thermoplastic Natural Rubber (TPNR)/Strontium Titanate (SrTiO3) composites was determined at room temperature, 27oC using the Impedance Analyzer at frequencies 10 Hz to 1 MHz. TPNR is formed as the matrix while SrTiO3 acts as the filler. Six samples were prepared at percentages of fillers from 0 to 50% at 10% intervals. The results indicate that the dielectric constant is almost independent of frequency from 100 Hz to 1 MHz, but the dielectric loss factor decreased with increasing frequency. This could probably be due to interfacial polarization and ionic losses. The dielectric properties are also affected by the composition of the filler, SrTiO3.

Antimony trioxide was prepared, using antimony potassium tartarate as starting material, via forward and reverse precipitation technique. The characteristics of the resulting antimony oxides were determined by BET surface area method, differential thermogravimetry analysis (DTG), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and SEM. The DTG curves for all uncalcined samples showed only a single endothermic peak which indicated that the sample is antimony trioxide. Unlike forward precipitation technique which resulted in a single antimony trioxide phase which is senarmontite, reverse precipitation technique produced antimony trioxide with both senarmontite and valentinite phase. Upon calcinations at 723 K, a small amount of Sb2O4 with cervantite phase was formed at the expense of Sb2O3 senarmontite phase as detected from the XRD pattern and infrared spectrum of RSb. The effect of preparation route on the properties of the antimony trioxide produced was clearly demonstrated.