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Catalyst Immobilization methods are important for providing better recovery of catalyst in photocatalytic treatment. The aim is to characterize and evaluate the photocatalytic performance of TiO2/ZnO-coated clay beads. The titanium dioxide/zinc oxide (TiO2/ZnO)-coated clay beads were prepared via the sol-gel process. Various ZnO powder ratios gave different TiO2/ZnO composites sol. Four layers of TiO2/ZnO sol were coated on clay beads and dried in the oven at 100°C for 30 min. The coated clay beads were calcined at 500°C for one hour for every two layers. Characterization of coated clay beads was done using a scanning electron microscope and energy dispersive spectroscopy. The increased surface area on small agglomeration and optimum loading of ZnO (5 g) resulted in the highest degradation efficiency recorded at 86.57%. An effective catalyst immobilization achieved a good recycling performance on clay beads. Degradation rate data were presented by pseudo-first-order kinetics. It was observed that the average degradation rate for TiO2/5 g ZnO is 0.00836 min–1. The actual results in this work can be applied as a guideline for the preparation of TiO2/ZnO-coated clay beads with high photocatalytic performance.

In this study, the biomass of banana peel was used to produce pectinase via optimization of solid-state fermentation conditions of the filamentous fungi Aspergillus nigeA. niger). The operating conditions of solid-state fermentation were optimized using the method of full factorial design with incubation temperature ranging between 25 °C and 35 °C, moisture content between 40% and 60%, and inoculum size between 1.6 x 106 spores/mL and 1.4 x 107 spores/mL. Optimizing the solid-state fermentation conditions appeared crucial to minimize the sample used in this experimental design and determine the significant correlation between the operating conditions. A relatively high maximal pectinase production of 27 UmL-1 was attained at 35° C of incubation, 60% of moisture content, and 1.6 x 106 spores/mL of inoculum size with a relatively low amount of substrate (5 g). Given that the production of pectinase with other substrates (e.g., pineapple waste, lemon peel, cassava waste, and wheat bran) generally ranges between 3 U/mL and 16 U/mL (Abdullah et al., 2018; Handa et al., 2016; Melnichuk et al., 2020; Thangaratham and Manimegalai, 2014; Salim et al., 2017), thus the yield of pectinase derived from the banana peel in this study (27 U/mL) was considered moderately high. The findings of this study indicated that the biomass of banana peel would be a potential substrate for pectinase production via the solid-state fermentation of A. niger.

Membrane technology is important in industrial wastewater and water treatment. Recently, the polymeric membrane technology is widely chosen in these applications. However, they are lowtemperature ranges, low corrosion resistance, and low lifespan. Thus, researchers are actively trying to develop a better membrane technology such as natural clay ceramic membrane due to their excellent in chemical, mechanical and thermal resistance, high-pressure application and long lifespan. This detailed review compiles through the literature of current scientific research over the last ten years. Its highlights the key findings of factors in the fabrication of natural clay ceramic membrane that contributed to its properties. This review article presented an outline of the advantages, disadvantages, and how to overcome the disadvantages, structure, and preparation of ceramic membrane, including method, raw materials, drying and sintering temperature. The review confirmed that the sintering temperature, the composition of raw materials and pore-forming agent are significantly enhanced the mechanical strength and porosity of the natural clay ceramic membrane. However, further development and modification of the natural clay ceramic membrane technology and their applications to treat different environmental pollutants is still necessary.

More than 320 million tons of plastics are produced annually, and the rate of plastic waste generation steadily increases by 3.9% per year. Introduction of plastic waste into water bodies may lead to many adverse environmental impacts as the plastic debris is very stable and generally requires a longer time to degrade. Over a period of time, bulk plastic debris will slowly degrade into small fragments known as macroplastics (particles size >5mm) and microplastics (particles size

Biofouling and biofilms exist as ubiquitous, undesirable accumulation of flora and fauna upon a given substrate when being immersed into an aquatic medium. Therefore, a novel antifouling based materials with the incorporation of nanotechnology has been developed for the prevention of biofouling in its initial stage through photocatalytic treatment. This study investigated the antimicrobial properties of photoactive Cerium (Ce) doped ZnO powder and explores its potential properties for future antifouling application. ZnO nanoparticles was doped with 0.4 mol% Ce was synthesized through the combination of modified citrate gelation technique and solid state sintering. The successful preparation of Ce doped ZnO was confirmed by XRD and SEM. The antimicrobial activity of Ce doped ZnO against E. coli and S. aureus was determined through antibacterial susceptibility test by agar well diffusion method whilst its photocatalytic inactivation efficiency against selected bacteria was analysed through photodegradation testing under UV light irradiation. The findings demonstrated that the synthesized Ce doped ZnO powder exhibited antibacterial effect against Gram-positive bacteria (S. aureus) and excellent photocatalytic efficiency to inactivate both Gram-negative (E. coli) and Gram-positive (S. aureus). 2 g/L of Ce doped ZnO catalyzed the 100% disinfection of both bacteria in 180 min of UV light exposure. Thus, this proved that Ce doped ZnO powder has the potential as efficient antifouling agent.

Metal corrosion generally refers to metal deterioration process that is caused by electrochemical reactions between the metallic substrate with corrosive environment. Marine grade stainless steel type 316L (SS 316L) is a premium material for marine applications. Prolonged exposure to chloride-containing environments increases the susceptibility of unprotected SS 316L to localized corrosion namely pitting and crevice corrosion. In this study, the potential protective coating comprising of the epoxy matrix with ZnO nanoparticles combination was formulated and its anticorrosive properties on SS 316L substrate were analyzed. Variation in corrosion behaviour of SS 316L coated with a series of epoxy coating solution containing 1, 3, 5, 7 and 10 wt % ZnO nanoparticles were thoroughly observed. The coating formulations were characterised by using X-ray Diffraction (XRD) spectroscopy and Scanning Electron Microscope (SEM). Meanwhile, the corrosion performance testing was measured by using Potentiodynamic Polarization (PP) technique. The results revealed that epoxy coating incorporated with 3 wt % of ZnO nanoparticles provided the best corrosion protection on SS 316L as the corrosion rate for the metal substrate has been minimized from 0.05268 mm/year to as low as 0.00047 mm/year after coating. Dispersion of ZnO nanoparticles in epoxy matrix increases the barrier properties of the coating and impeded corrosion process on SS 316L through suppression of anodic reaction.

Cerium (Ce) doped ZnO is a promising material for advanced photocatalysis. It is useful for inducing the treatment of many organic pollutants in water. However, the stability of its performance under varying temperature and saline condition has never been not fully assessed. In this study, powder form photocatalyst comprising 99.0 mol% ZnO and 1 mol% CeO2 has been synthesized via modified citrate gelation technique and solid-state sintering at 1200 °C for 5 hours. The conversion of Ce doped ZnO from its precursors has been confirmed using XRD, SEM, and EDX techniques. The photocatalytic efficiency of the synthesized Ce doped ZnO under UV-C light (λ=265 nm) was determined. In the experiment, the operating temperature was varied between 25 to 40 °C, and the salinity of the treated solution was increased from 0 to 40 g/L NaCl. The findings revealed that the photocatalytic efficiency of Ce doped ZnO under UV light improved from 78.2% to 88.6% as the temperature increased from 25 to 40 °C. The performance of Ce doped ZnO decreased from 86.7% to 36.7% when the salinity increased from 0 g/L to 40 g/L. The elevation of temperature encouraged the photogeneration of electron-hole pairs on catalyst surface while the presence of chloride ions in treated medium caused scavenging of hydroxyl radicals or hole.

Semiconductor oxides such as titanium dioxide (TiO2) and zinc oxide (ZnO) are used as the photocatalyst for removing contaminants. In addition, TiO2 and ZnO nanoparticles in the suspension form makes it difficult to be recovered and recycled. This study was conducted to investigate the efficiency of immobilizing TiO2 and ZnO nanoparticles in epoxy beads. The immobilization process using different ratios of photocatalysts TiO2/ZnO (1:0, 3:1, 1:1, 1:3 and 0:1) fixed on epoxy material. These epoxy beads were used for dye removal in photocatalysis using methylene blue (MB) solution at a concentration of 10mg/L. Besides, epoxy beads also characterized using scanning electron microscope (SEM), attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy and thermogravimetric analysis (TGA). The results showed that the highly recommended epoxy bead is 3:1 ratio of TiO2/ZnO because it has good performance in dye degradation that proved from reducing concentration of MB to 2.4mg/L (76%). However, TiO2/ZnO characterization of 3:1 by SEM show on the surface the particle are found to be spherical in shape which is relatively high efficiency for the degradation, ATR-FTIR pattern in broad band 4000 cm-1 - 400cm-1 which correspond to hydroxyl stretching to be adsorbed at peak (474.49 cm-1 - 3722.61cm-1) respectively to the optimum for the degradation and TGA rate of change are 5mg to 2.5mg that residue (49.78%) due to decomposition or oxidation from mass loss. These findings are very effective and economical technique to be cost saving and highly efficient photocatalyst.

With the trend for green technology, the study focused on utilizing a forgotten herb to produce an eco-friendly coating. Andrographis paniculata or the kalmegh leaves extract (KLE) has been investigated for its abilities in retarding the corrosion process due to its excellent anti-oxidative and antimicrobial properties. Here, KLE was employed as a novel additive in coatings and formulations were made by varying its wt%: 0, 3, 6, 9, and 12. These were applied to stainless steel 316L immersed in seawater for up to 50 days. The samples were characterized and analyzed to measure effectiveness of inhibition of corrosion and microbial growth. The best concentration was revealed to be 6 wt% KLE, it exhibited the highest performance in improving the ionic resistance of the coating and reducing the growth of bacteria.

Solar photocatalysis is a green technology that takes advantage of sustainable solar energy for enhancing oxidation process of numerous harmful water contaminants. In this study, a custom solar driven zinc oxide (ZnO)-mediated photocatalytic system was developed and its efficiency to remove organic contaminants as well as to disinfect selected bacteria was investigated. Methylene blue (MB) dye was used as the model organic contaminant, while Escherichia coli (E.coli) was used as the model fecal coliform bacteria in contaminated water. A series of photodegradation experiments were conducted on water contaminated with either 10 mg/L of MB or ~1010 CFU/ml of E.coli. The experiments were completed under sunlight irradiation in the presence of 1 g/L of nano ZnO photocatalyst for up to 6 hours. Using a solar thermal collector, the photoreactor operated in the temperature range of 25 to 50 oC. The findings revealed that the combination of solar thermal with solar photocatalysis using ZnO intensified the degradation of MB and disinfection of E.coli. 98.08% of MB dye and 99.99% of E.coli were successfully removed from the water within the first 3 hours of treatment. Almost complete removal was eventually achieved after 6 hours of treatment. It is therefore suggested that ZnO-based solar photocatalytic system developed in this study is highly efficient at enhancing water decontamination process.

Agriculture waste has attracted attention as a potential source to produce raw material silicon dioxide, either crystalline (pyrophyllite) or amorphous form (geothermal sludge). It is an unwanted waste produced as a desired result of agricultural activities. Nanosilicon dioxide has undoubtedly gained eager interest in many vital industries. It is renowned for positively enhancing outstanding performance due to tuneable properties over its bulk counterpart. Silicon dioxide scientifically demonstrates a unique ability to convert efficiently into economic value from silicon-rich agriculture waste. Thus, a noble extraction from silicon-rich waste is undoubtedly gaining enormous attention. However, adequate knowledge on local optimisation of nanosilicon dioxide extraction from silicon-rich agriculture waste is lacking. Specific aims of this comprehensive review mainly highlighted a synthesis method of potential nanostructured silicon dioxide from agriculture waste and their potential applications for plant growth promoters. Reverse microemulsion, chemical vapour condensation, solid gelation, and mechanochemical are preferred methods that were typically specified to focus this comprehensive review critically. Optimisation of nanosilicon dioxide can be achieved precisely via the ideal combination of solid gelation and a high-energy ball mill process. Silicon dioxide is undoubtedly an effective agent as a plant growth promoter to overcome biotic and abiotic factors such as heavy metal uptake and translocation, inhibit pathogenic fungi, improve the antioxidant system, and mitigate various stress factors.

This paper investigated the effects of Pr6O11 and Co3O4 on the electrical properties of ZnO-BaTiO3 varistor ceramics. The Pr6O11 doping has a notable influence on the characteristics of the nonlinear coefficient, varistor voltage, and leakage current where the values varied from 2.29 to 2.69, 12.36 to 68.36 V/mm and 599.33 to 548.16 µA/cm2, respectively. The nonlinear varistor coefficient of 5.50 to 7.15 and the varistor voltage of 7.38 to 8.10 V/mm was also influenced by the use of Co3O4 as a dopant. When the amount of Co3O4 was above 0.5 wt.%, the leakage current increased from 202.41 to 302.71 μA/cm2. The varistor ceramics with 1.5 wt.% Pr6O11 shows good nonlinear electrical performance at higher breakdown voltage and reduced the leakage current of the ceramic materials. Besides, the varistor sample that was doped with 0.5 wt.% Co3O4 was able to enhance the nonlinear electrical properties at low breakdown voltage with a smaller value of leakage current.

This paper investigated the effects of Pr6O11 and Co3O4 on the electrical properties of ZnO-BaTiO3 varistor ceramics. The Pr6O11 doping has a notable influence on the characteristics of the nonlinear coefficient, varistor voltage, and leakage current where the values varied from 2.29 to 2.69, 12.36 to 68.36 V/mm and 599.33 to 548.16 µA/cm2, respectively. The nonlinear varistor coefficient of 5.50 to 7.15 and the varistor voltage of 7.38 to 8.10 V/mm was also influenced by the use of Co3O4 as a dopant. When the amount of Co3O4 was above 0.5 wt.%, the leakage current increased from 202.41 to 302.71 μA/cm2. The varistor ceramics with 1.5 wt.% Pr6O11 shows good nonlinear electrical performance at higher breakdown voltage and reduced the leakage current of the ceramic materials. Besides, the varistor sample that was doped with 0.5 wt.% Co3O4 was able to enhance the nonlinear electrical properties at low breakdown voltage with a smaller value of leakage current.

Leucaena leucocephala leaves extract (LLE) was incorporated as an additive in a new coating formulation. The coatings containing different wt.% of the extracts were analysed by optical characterizations and we proceeded to the antimicrobial assessment. The coating was applied onto the surface of stainless steel grade 316L and immersed in seawater for 50 days. A batch of specimens was collected every 10 days and evaluated through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and scanning electron microscope with energy dispersive X-ray (SEM/EDX). The incorporation of 3 wt.% LLE into the coating (P2) matrix remarkably boosted the barrier quality of the coating.

The zinc oxide based varistor are widely used as circuit protective devices by literally absorbs these dangerous surges and spikes or grounding this unwanted magnitudes. In this research, zinc oxide is added with 0.5 mol % CaMnO3 as an additive and 0.2 mol % of rare earth doped of lanthanum oxide. Citrate-gel method is used as fabrication method. Complex compound undergoes sintering process which varied at 900 °C, 950 °C and 1000 °C, while, the sintering time are setting at 1 hour and 2 hours. Thermo gravimetric analysis (TGA) shows the forming of CaMnO3 at 334-1000 °C. Fourier Transform Infrared (FTIR) spectra proved that the functional group present are.-O-H, C-H and C-O. The surface morphology with the grains size below 1μm was observed by Scanning Electron Microscopy (SEM). The α varistor ceramics was calculated from data analysis of I-V characteristics obtained through a Source Measure Unit (Keithley 236). The calculation of α is done by using Origin Pro8.0 software. I-V characteristic shows the value of α in the range of 1.00 to 4.05.

The vulnerability of varistor ceramics to electrical degradation during operation not only affects their nonlinear properties but also leads to shortening of device’s lifetime by increasing the risk of failures including melting, fire or even explosions. In this study, ZnO-Pr6O11-Cr2O3 varistor ceramics were prepared through modified citrate gel method and solid state-sintering at 1250 °C for 1 hour. The stability of their nonlinear properties under prolonged application of DC electrical field in high temperature ambient was investigated. Degradation process was accelerated by applying direct current (DC) electrical field of 15 % below the breakdown field point of ceramics for 54 hours consecutively at temperature of 30 to 125 °C. The findings indicate that ZnO-Pr6O11-Cr2O3 ceramics exhibited its susceptibility to electrical degradation after prolonged electrical and thermal stresses application. Its nonlinear coefficient has reduced by 4.4 % reduction, the breakdown field has reduced by 9.9 % and the leakage current density increased by 13.7 % in comparison to its initial value. Degradation process in varistor ceramics of ZnO-Pr6O11-Cr2O3 was a direct response to collapsed Double Schottky Barrier at ZnO grain boundary.

Steel corrosion and biofouling have adverse impacts on various high-end engineering applications including, in biomedical and maritime industries. Smart functional polymer coatings have been developed to simultaneously control corrosion and prevent biofouling problems on steels. In this study, translucent epoxy coatings loaded with 1, 3, and 5 wt% of functional hybrid composite (HC) microparticles were formulated. The HC particles contained cerium doped ZnO encapsulated in conductive poly(3,4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT: PSS) polymer at mixing ratio of 3:1. The effects of HC composition towards the corrosion inhibition and antifouling properties of the coating were evaluated. The microstructure and composition analyses were performed by using SEM and EDX techniques. The anticorrosion performance of the coating films deposited on stainless steel (SS 316 L) substrates was evaluated by using the Potentiodynamic Polarization (PP) technique. The antifouling characteristics of the coatings were investigated by performing the antimicrobial susceptibility test and a series of photodegradation test in medium containing ∼108 CFU/ml of bacteria under UV light in 180 minutes. The findings revealed that the presence of PEDOT:PSS-Ce doped ZnO HC increased the barrier properties of the epoxy matrix on SS 316 L against corrosion. The corrosion inhibition properties increased with increasing HC composition. The formulated coatings also exhibited antifouling effects against bacteria. The Gram positive-S. aureus exhibited susceptibility against the coating whereas the Gram negative – S. aureus showed resistant. The coatings demonstrated photocatalytic properties under UV light irradiation and capable of inactivating

Palm slag in previous studies has proven to have the potential to be used as alternative filler in friction composite. However, the reported hardness is still high and not within the proper range and might cause damage to the disc brakes. As is well known, the good damping, soft and flexible nature of rubber, being the main reason for waste tire dust to be selected as an additive to reduce or moderate the hardness of friction palm slag composite. Weight percentage and the filler size of waste tire dust used are the main parameters considered in this research paper. The hardness and wear rate of the friction composite produced are measured. The result revealed that friction composite with ratio of palm slag/waste tire dust (30/10) and the highest filler size (>600 µm) give a moderate hardness with better wear rate which comparable with the commercial brake pad used. Morphological view also give a prove that the worn surface of composite have less wear defects. Overall the used of waste tire dust can improve the hardness and wear rate properties of palm slag friction composites in order to become alternative for non-asbestos brake pads.

In this research, (80-x) mol% zinc oxide with 20 mol% CaMnO3 as the additive and (x) mol% erbium oxide Er2O3 as the doping material where x = 0.5, 1.0 and 1.5. Aims of this work are to elucidate the effects of doping material on microstructure ZnO and nonlinear characteristics of ZnO based varistor ceramics. A compound comprising ZnO-CaMnO3-Er2O3 underwent pre-sintering at 500 °C for 4 hours and sintering process at temperature of 1100 °C, 1200 °C and 1300 °C with the soaking time of 1.5 hours and 4.5 hours. X-ray diffraction patterns CaMnO3 spinal and additional phases containing Er in the confirmed the presence of synthesized compounds.The disappeared of hydroxyl and carbonyl functional group was observed at 3600-3650 cm-1, 1421 cm-1 and 875 cm-1 respectively by Fourier Transform Infrared spectroscopy to indicate the starting formation oxide metal upon calcinations.Keywords: ZnO varistor; Er doping; microstructure; I-V characteristics; low voltage varistor

In the ZnO based varistor, the improvement of nonlinear coefficient (α) and prevention of evaporation of Bi2O3 during heat treatments can be achieved by the addition of MnO2 or Co3O4. In this conjunction, it is proper to see the effect of these additives at different low mol percentage and sintering conditions to nonlinear coefficient improvement of the varistor ceramics. In this paper, the investigation regarding to the α variation of Co3O4 doping on ZnO-Bi2O3-TiO2 system is discussed. Here, the crystalline phases were identified by an XRD (PANalytical (Philips) XPert Pro PW3040/60) with CuKα radiation and the data were analyzed by using XPert High Score software. The density of varistor ceramics was measured by the geometrical method. The current-voltage characteristics of the varistor ceramics were evaluated. The average grain size (d) was determined by lineal intercept method. The α of ZnO doped with 0.5 mol% of Bi2O3, 0.5 mol% of TiO2 and x mol% of Co3O4 was calculated from data analysis of current-voltage characteristics obtained through a Source Measure Unit (Keithley 236). The calculation of α is done by using Origin Pro8.0 software. The value of α at low concentration at 1170 °C has the value 5.36 and 3 at 45 and 90 min sintering time, respectively, and then decreases to 4.99 and 2.98 at 0.8 mol% Co3O4 concentrations. When the amount of dopant is increased then the value of α increase up to 0.4 mol% and then the value are slightly dropped after further addition. The addition of Co3O4 dopant in Zn-Bi-Ti oxide ceramics sintered at 45 minutes cause the value of α to increase up to 0.4 mol% and decrease after further addition.

It is necessary to investigate the electronic states of ceramic based ZnO vasristor and effect of doped impurities at different concentration. Band gap (Eg) of the ceramic (99-x) mol% ZnO+0.5 mol% Bi2O3+0.5 mol% TiO2+ xCo3O4 where x = 0, 0.2, 0.4, 0.6 and 0.8 mol%, were determined using UV-Vis spectrophotometer. The samples were prepared via solid-state route and sintered at the sintering temperature at 1110, 1140 and 1170 °C for 45 and 90 min in open air. At no doping of Co3O4, the values of Eg are 2.991 ± 0.001, 2.989 ± 0.001 eV for 45 and 90 min sintering time; respectively. Eg was decreased to 2.368 ± 0.002 and 2.352 ± 0.001 eV at 0.8 mol% Co3O4 for 45 and 90 min sintering time; respectively. XRD analysis indicates that two main phases existed at all concentrations which are ZnO and secondary phases, Bi12TiO20, Zn2Ti3O8, ZnCo2O4 and Co3Ti3O. Relative density decreases with the addition of Co3O4 compared to that of undoped at all doping level. When Co3O4 is added in the ceramics, relative density increases with the increase of doping level at both 45 and 90 min sintering time. The variation of sintering temperatures and XRD findings of steepness factor are correlated with the UV-Vis spectrophotometer results of based ZnO varistor doped with Co3O4 due to the growth of interface states.

Zinc oxide based varistor are widely used as circuit protective devices by literally absorbs these dangerous surge and spikes or grounding this unwanted magnitudes. In this research, zinc oxide is added with 20 mol% calcium manganite (CaMnO3) as an additive and Cobalt oxide (CoO) as doping material. Citrate-gel method is used as fabrication method compared to conventional solid-state method. This compound (ZnO-CaMnO3 -CoO) undergoes pre-sintering at 500 °C for 2 hours. In the sintering process, sintering temperature at 1300 °C, while the sintering time are setting at 1.5 hours. X-ray diffraction (XRD) patterns shows the components and phases of the compounds. The change of functional group was observed by Furrier transform infra-red (FTIR). I-V characteristic shows the value of nonlinear coefficient in the range of 1.0-2.0.

Zinc oxide based varistor are widely used as circuit protective devices by literally absorbs these dangerous surge and spikes or grounding this unwanted magnitudes. In this research, zinc oxide is added with 20 mol% calcium manganite (CaMnO3) as an additive and cobalt oxide (Co3O4) as doping material. Citrate-gel method is used as fabrication method compared to conventional solid-state method. This compound (ZnO-CaMnO3-Co3O4) undergoes pre-sintering at 500 °C for 2 hours. In the sintering process, sintering temperature at 1300 °C, while the sintering time are setting at 1.5 hours. X-ray diffraction (XRD) patterns show the components and phases of the compounds. The change of functional group was observed by Fourier Transform Infrared (FTIR). I-V characteristic shows the value of nonlinear coefficient in the range of 1.0-2.0.

The work aims the improvement of nonlinear coefficient ( ) can achieve by the addition of MnO 2 . The investigation regarding to the variation of MnO 2 doping on ZnO-Bi 2 O 3 -TiO 2 system is discussed. The crystalline phases were identified by an XRD (PANalytical (Philips) X’Pert Pro PW3040/60) with CuK radiation and the data were analyzed by using X’Pert High Score software. The density of varistor ceramics was measured by the geometrical method. The current-voltage characteristics of the varistor ceramics were evaluated. The average grain size ( ) was determined by lineal intercept method. The of ZnO doped with 0.5 mol% of Bi 2 O 3 , 0.5 mol% of TiO 2 and x mol% of MnO 2 was calculated from data analysis of current-voltage characteristics obtained through a Source Measure Unit (Keithley 236). The calculation of is done by using Origin Pro8.0 software which at low concentration at 1170 o C has the value 10.36 and 9.21 at 45 and 90 min sintering time, respectively, and then decreases to 5.63 and 5.27 at 0.8 mol% MnO 2 concentrations. The addition of MnO 2 dopant in Zn-Bi-Ti oxide ceramics sintered at 45 minutes cause the value of to increase up to 0.4 mol% and decrease after further addition.

In this study, the optical band-gap energy (Eg) was investigated with respect to MnO2 and sintering temperatures on ZnO based varistor ceramics. Eg of the ceramic (99-x) mol% ZnO + 0.5 mol% Bi2O3 + 0.5 mol% TiO2 + × MnO2 where × = 0, 0.2, 0.4, 0.6 and 0.8 mol%, were determined using UV-Vis spectrophotometer. The samples was prepared through solid-state route and sintered at the sintering temperature from 1110, 1140 and 1170 °C for 45 and 90 min in open air. At no doping of MnO2, the values of Eg are 2.991 ± 0.001, 2.989 ± 0.001 eV for 45 and 90 min sintering time; respectively. Eg was decreased to 2.192 ± 0.001 eV at 1140 °C at 45 min sintering time. Similar result of Eg was observed at longer heat treatment. Further addition of dopant causing the Eg decreases rapidly to 2.099 and 2.106 ± 0.001 eV at 45 and 90 min sintering time; respectively. XRD analysis indicates that there is hexagonal ZnO and secondary phases, Zn2MnO4, Bi4Ti3O12 and Zn2Ti3O8. The relative density of the sintered ceramics decreased or remain constant with the increase of MnO2 concentration for 45 min sintering time, however, further prolong sintering time; the relative density decreases form 90.25 to 88.35%. This indicates the pores are increasing with the increase of heat treatment. The variation of sintering temperatures to the optical band gap energy of based ZnO varistor doped with MnO2 due to the formation of interface states.

CdTe film was deposited using the electrophoretic deposition technique onto an ITO glass at various bath temperatures. Four batch film compositions were used by mixing 1 to 4 wt% concentration of CdTe powder with 10 mL of a solution of methanol and toluene. X-ray Diffraction analysis showed that the films exhibited polycrystalline nature of zinc-blende structure with the (111) orientation as the most prominent peak. From the Atomic Force Microscopy, the thickness and surface roughness of the CdTe film increased with the increase of CdTe concentration. The optical energy band gap of film decreased with the increase of CdTe concentration, and with the increase of isothermal bath temperature. The film thickness increased with respect to the increase of CdTe concentration and bath temperature, and following, the numerical expression for the film thickness with respect to these two variables has been established.