Mohd Syafiq Zulfakar

ZnAl2O4-Based Microwave Dielectric Ceramics as GPS Patch Antenna: A Review

This paper describes the potentials of zinc aluminate (ZnAl2O4) based microwave dielectric ceramics as patch antenna for GPS applications. Nowadays the GPS operating frequencies has been shifted from microwave technology to millimeter-wave technology. Various microwave dielectric ceramics (MDC) have been explored and widely used in telecommunication industries. Among the most interesting materials of that kind, zinc aluminate (ZnAl2O4) is recognized as one of the most promising non-metals and offers many advantages as GPS patch antenna. By modifying ZnAl2O4 compound with other materials, it is found to have high quality factor (Q>5,000), low dielectric constant (εr<20), and near zero temperature coefficient of resonant frequency (τf∼0). The studies also evidence the typical value of εr for GPS patch antenna and microwave substrate in the range of 4<εr<20 and 4<εr<10, respectively. The study also shows that the ZnAl2O4-based MDC can be successfully fabricated as microstrip patch antenna, which meets the requirements of GPS application.

Effect of Zn Site for Ca Substitution on Optical and Microwave Dielectric Properties of ZnAl2O4 Thin Films by Sol Gel Method

( = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30) thin films were prepared by a sol gel method. The XRD patterns displayed the characteristic peaks of (Ca/Zn)Al2O4 with the standard pattern of face-centred cubic (fcc). The addition of Ca decreased the lattice constant from 14.6 nm to 23.2 nm. The optical bandgap of undoped thin film was found to be at 3.84 eV while for doped Ca was observed at 3.50 to 3.73 eV. The substitution of Zn2

Morphology and Optical Studies of (1-x)ZnAl2O4 – xSiO2 Thin Films Prepared by Sol-Gel Method

The effect of morphological structures and optical band gap of (1-x)ZnAl2O4xSiO2 samples with compositions of x = 0.00, 0.05, 0.10 and 0.15 were prepared by sol-gel method. Spin coating technique was used to deposited the (1-x)ZnAl2O4xSiO2 as a thin film and to investigate the structural and optical band gap. The produced thin film samples were annealed at 450 °C for 1h. Field emission scanning electron microscope (FESEM) was used to investigate the surface morphology of the samples. The average particle size for (1-x)ZnAl2O4xSiO2 is about 331.23 nm. The particle size are tend to increase as the composition of SiO2 increased. XRD analysis shows the formation of cubic structure phase and dominant peak has been observed with Miller Indices (311) plane. The average crystallite size, D was calculated with average size about 8 13 nm. The optical band gap was calculated for (1-x)ZnAl2O4xSiO2 samples and it was found within range of 3.34 to 3.94 eV.

Fabrication and Characterization of TiO2-Doped ZnAl2O4 Nanocrystals via Sol-Gel Method for GPS Antenna

The Zn(1-x)TixAl2O4 (x = 0.00, 0.05, 0.15 & 0.25) nanocrystals thin films were prepared by sol-gel method. The properties of Zn(1-x)TixAl2O4 were investigated by X-ray diffraction (XRD), Atomic Force Microscope (AFM), Fourier transform infrared spectra (FTIR) and (UV-Vis). By indexing the XRD patterns, we identified three structural types which is ZnAl2O4, anatase and rutile. The addition of TiO2 increased the crystallite size from 14.65 to 25.25 nm. The direct band gap was found to be around 3.35 to 3.84 eV. The addition of TiO2 increased the crystallite size, surface roughness, and lattice parameters of the resultant films, evidently affecting their density and dielectric constant (). The thin films were characterized in the certain frequency to determine the using LCR spectrometer. The and density value of the Zn(1-x)TixAl2O4 films increase linearly from 8.56 to 13.48 and 4.60 to 4.70 g/cm3 with the increasing of x value, respectively. Based on the material analysis and microwave antenna theory, GPS patch antennas were fabricated using the Zn(1-x)TixAl2O4 material. The fabricated GPS antenna with the highest (13.48) material exhibits the smallest size of antenna which is 7.45 cm2. The performances and the operating frequencies were measured using a PNA series network analyzer. The result showed that all patch antennas operate at frequency of 1.570 GHz. The GPS patch antenna fabricated from Zn0.25Ti0.75Al2O4 showed an excellent combination of return loss (-29.6 dB), smallest size (7.85 cm2), and wide bandwidth (195 MHz). All fabricated antennas are meets the requirements of GPS applications.

Characterizations of natural dye from garcinia mangostana with graphene oxide (GO) as sensitizer in dye-sensitizer solar cells

Usage of natural product in improvement of dye-sensitized solar cell (DSSC) have been look upon in research field. There is numerous different type of nature product was used as natural dye but the performance of DSSC with natural dye are low efficiency compare to DSSC with Ruthenium (II) dye due to low anchoring strength between dye molecule with TiO2 surface. This paper is about an experiment DSSC device with sensitizer of Mangosteen with Graphene Oxide as catalyst. The highest device efficiency with graphene oxide (GO) concentration of 0.50 mg/ml obtained in this experiment is 0.40% with short-circuit current density (Jsc) = 1.00 mA/cm2, open circuit voltage (Voc) = 0.61 V and fill factor(FF) = 65.72%. It shows that GO helped to increase device performance by increase the ability of sensitizer absorbed onto TiO2 and adding more passageway for carriers movement between TiO2 surface and dye sensitizer.

Review on recent performance titanium dioxide for flexible dye sensitized solar cell

Flexible dye sensitized solar cell offers an easy implemented technology for future energy supply and gives more benefits compared to the conventional silicon solar cells. The properties of flexible substrates very unique that can some advantages compared to the rigid substrate. In this review, the focused was on recent achievement on flexible dye sensitized solar cell with titanium dioxide as the best material that being used as photoanode material.

Influence Different Compositions of (1-x)ZnFe2O4 – xSiO2 Nanostructures Thin Film Synthesized by Sol-Gel Method

SiO2 compound was introduced into zinc ferrite using formula (1-x)ZnFe2O4 – xSiO2 synthesized by sol-gel method where distilled water and citric acid was used as a solvent and binder agent. The produced samples were annealed at 450 °C for 1h. The AFM result analysis show that the average surface roughness and particle size decreased as the compositions of x was increased. XRD results analysis confirmed the formation of spinel structures with crystallite size within range 11.27 – 4.72 nm. UV-Vis analysis to determine the energy band gap of the (1-x)ZnFe2O4 – xSiO2 samples. It shows that the energy band gap increased as the composition of SiO2 was increased due to the dielectric properties of silicon dioxide. FTIR results analysis exhibit common band in the range of 400 – 4000 cm-1. The observed band near 2350 cm-1 shows the presence of oxygen-oxygen bond in the face centered cubic (fcc) crystal lattice of oxygen atoms. The addition of SiO2 into ZnFe2O4 will help to enhance the morphological structures and optical properties. This new proposed dielectric material can be used as dielectric substrate microstrip patch antenna.

Performance Effect of ZnAl2O4 - SiO2 Thin Film for Wireless Patch Antenna Application

Polycrystalline of (1-x)ZnAl2O4 – xSiO2 compound with compositions of x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.25 have been prepared using sol-gel method. Structural properties was investigated by atomic force microscopy (AFM) and x-ray diffractometer (XRD). The AFM images analysis showed that the surface roughness of the highest composition had rougher surface compared with other samples. XRD measurement indicated that the crystallite size also increased with average crystallite size around 18 nm with cubic phase had been found. The dielectric permittivity value were measured with frequency range of 1 Hz to 1 MHz. It is showed that the dielectric value decreased as the freqeuncy was applied to the samples. The performance of the patch antenna showed that the antenna resonated at 3.30 GHz and give-13.87 dB with frequency range about 2 – 4 GHz.