Materials Science Forum Vol. 846

Abstract: Many trivalent rare earth ions such as Er³⁺, Tm³⁺, Ho³⁺, Pr³⁺ and Nd³⁺ were doped as absorption and emission centers in glass hosts. In this work, lead borotellurite (PBT) glass doped with neodymium ion (Nd³⁺) has been prepared and characterized by mean of their optical properties. The UV-Vis measurement has been carried out in order to determine the optical band gap energy, reflective indices and the polarizability. Optical absorption spectra of the glass samples are recorded in the range 400–900 nm at room temperature From the result, there are six significant absorption peaks that corresponds to 525 nm, 584 nm, 683 nm, 747 nm, 805 nm and 878 nm wavelength have been observed with the most predominant peak to be used as excitation wavelength is found centered at 584 nm. The energy band gaps as well as the refractive indices were found to vary from 2.50eV to 2.59eV and from 1.89 to 1.96 with mol% of Nd content respectively. Meanwhile, the polarizability shows a similar trend of results to refractive indices as it varies from 5.56 x 10^-24 cm³ to 5.63 x 10^-24 cm³. These results will be discussed further in details.

Abstract: Ceramic materials based on cerate-zirconates have potential application as a solid electrolyte in electrochemical devices such as fuel cells and hydrogen sensors. To become a good electrolyte, the material must exhibits high density sample with homogenize grain size. In this study, we systematically investigated the microstructure of Ba (Ce,Zr)O₃ pellet as a function of sintering temperature. The calcined powder was compressed to become a pellet using hydraulic press with pressure of 5 tons for 5 min. Two-step sintering (TSS) process was applied for the densification of Ba (Ce,Zr)O₃ pellet. The first temperature profile was fixed at T₁ = 1400°C and the second temperature profile was varied from T₂ = 1150°C, 1200°C, 1250°C, 1300°C and 1350°C, respectively. The sintered sample at T₂ = 1350°C showed the highest density compared to others. Its relative density was 82.50%. The lowest density was 64.38% for the sintered sample at T₂ = 1150°C. However, the densification of pellet showed an irregular behavior at T₂ = 1300°C. It might be related to the de-densification phenomenon due to the presence of carbonate species in the calcined powder. Microstructure of the fracture sintered pellet as observed by a scanning electron microscope (SEM) showed the grain size of the samples was in the range of 149.2–336.4 nm. For a comparison, green pellet and pellet prepared with conventional sintering step (CSS) were also discussed in this study.

Abstract: BaCe_0.54Zr_0.36Y_0.1O_2.95 (denoted as BCZY10) ceramic powder was synthesized by a modified sol-gel method using metal nitrate salts as precursors. The samples were prepared using two different types of surfactants which are cationic surfactant of hexadecyldimethylammonium bromide (HTAB), nonionic surfactant of polyoxyethylene (10) oleyl ether (Brij 97), and sample without surfactant as a control. All samples were labeled as S1, S2, and S3 respectively. They were dried and calcined at T=325 °C and T=1100 °C accordingly. Chemicals bonding of the compound were analyzed using Fourier transform infrared (FTIR) spectrometry and their phase formation was identified by X-Ray Diffractometer (XRD). All the dried samples showed the adsorption peak at 3200-3700 cm^-1 that related to the overlapping of OH stretching originated from –OH terminal group and N-H stretching vibrations. The peaks appeared at 1620-1640 cm^-1 can be assigned to C=O stretching and at 1380-1450 cm^-1 can be attributed for N-H bending vibration. The adsorption peak ≈500 cm^-1 of metal-oxygen bond for all the calcined samples became pronounces indicating that the metal complexes were transformed to metal oxides. XRD results confirmed that S2 and S3 formed a single-phase of Ba (Ce,Zr)O₃ perovskite type-oxide and S1 consists of multi-phases compound which are dominated by BaCeO₃, and BaZrO₃. Therefore, the used of different type of surfactant was found to give a significant effect on the synthesizing single-phase of BCZY10 ceramics compound.

Abstract: Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) is a ceramic perovskite-type oxide that has attracted growing attention due to its high catalytic activity, mixed ionic/electronic conductivity and giant magnetic resistance. Improvement in the properties of BSCF can be achieved by tailoring its architecture such as nanoparticles (powdered form), nanotubes or nanorods as these nanostructured materials posses high surface-to-volume ratios with high sensitivity to surface adsorption and reactions. However, most of the studies conducted by means of conventional solid-state reaction methods or with wet chemistry techniques regularly produced BSCF in loose powdered form, non-uniform and the particle size is hard to be controlled. Herein in this work, an investigation on a synthetic approach using highly ordered nanoporous anodic aluminium oxide (AAO) as a template, focusing on the fabrication of BSCF perovskite nanorods is demonstrated. Sol-gel method is used to prepare the BSCF precursor solution or sol followed by filling the AAO template with the sol at different immersion time of 1 hr, 12 hrs and 24 hrs. After the following drying and calcination steps, the morphological structure and composition of the synthesized BSCF nanorods inside the AAO templates are examined by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) analysis. The micrograph showed BSCF nanorods are successfully synthesized at immersion time of 24 hrs with the diameter of nanorods embedded in the AAO template is approximately 180 nm. The EDX analysis also confirmed the stoichiometry of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ. Possible formation mechanism of BSCF nanorods inside the AAO template is also discussed in this paper.

Abstract: In this study, β-wollastonite is produced from a reaction between silica (SiO₂) and calcium oxide (CaO) with the SiO₂/Cao ratio of 55:45. Rice straw ash is chosen as the source for SiO₂ instead of rice husk ash because the straw can yield up to 85% of silica even though this percentage is lower than those silica yielded from rice husk ash. It is found that period of autoclaving and sintering play an important role in producing the wollastonite. As shown in the XRD results, a single phase β-wollastonite is obtained after 8 h of autoclaving and 3 h of sintering at 950 °C. The produced β-wollastonite phase also shows a good crystallinity but needs longer sintering time compared with wollastonite produced using rice husk ash. DTA graph shows a chemical reaction between silica and calcium oxide started to occur at 788.3°C. IR spectroscopic analysis data confirm that the IR peaks at 681, 894 and 931 cm^-1 are due to the β-Wollastonite phase. Form the results obtained, it can be concluded that rice straw ash is comparable to rice husk ash as a precursor in producing β-Wollastonite material.

Abstract: A Polymer blends compose of Poly (3,4-ethylenedioxythiophene):Poly (styrene sulphonic acid)(PEDOT:PSS) and Polyaniline (PANi) have been prepared using drop casting technique. Optical parameters such as refractive index (n), extinction coefficient (k), reflectance, and optical dielectric were determined in this study. It is found that reflectance spectra increase as the PANi concentration decreases in the sample of small photon energy. The refractive index of the sample shows significant effect with the PEDOT:PSS concentration. As the concentration of PEDOT:PSS increases, the refractive index shows a normal dispersion behavior. Extinction coefficient decrease as the wavelength increase within the range of 300 nm to 350 nm that may contribute to the loss fraction of light due to scattering and the decreasing of absorbance at this range. However, the extinction coefficient increases from 350 nm to the maximum wavelength of 800 nm since the absorbance is also increasing. Both the real and imaginary part of the dielectric constant decreases when the photon energy increases. This revealed that the compositions of PEDOT:PSS influence the optical properties of hybrid PEDOT-PSS:PANi thin film.

Abstract: Silicon-based photonic devices have emerged as a high demand technology for a wide range of applications. Most of these devices can be realized by optical waveguides where it forms the basic structure for device construction. This project involved the optimization of silicon waveguide fabrication process modeling using Silvaco. The optimized silicon-based waveguide components are aimed to be implemented in future photonic devices such as optical modulators. The Taguchi methods are employed to study the influence of fabrication parameters variations on the fabrication performance such as etch rate and waveguide structure. Four fabrication parameters are investigated includes the diffusion temperature of the N - type channel, diffusion temperature of the P - type channel, silicon orientation and oxide thickness. The result shows that the temperature during the diffusion on an N - type channel has the most influence on the performance of the modulation efficiency of the silicon optical waveguide.

Abstract: ZnSe which show a potential application in electronic devices such as photovoltaic devices, light emitting devices and photodetector have been synthesized through a hydrothermal method using ZnCl₂ and Se powder as the source. In a typical synthesis, Zn²⁺ and Se^2- ion have been prepared separately and charged into a Teflon-lined stainless steel autoclave. The hydrothermal reaction was conducted at 180 °C for 32 hours. Structural properties of ZnSe are studied by X-ray diffraction (XRD) while the optical properties of ZnSe compound are characterized through ultraviolet–visible spectroscopy (UV-Vis). From the XRD result, pure ZnSe with main XRD peak at 2θ = 27.29°, 45.30°, 53.62°, 65.88°, 72.68° has been observed. The result have been supported by the optical results where absoprtion peak at 460 nm with optical band gap energy (Eg) at 2.5 eV.

Abstract: Porous silicon (PS) was successfully synthesized via novel integrated pulsed electrochemical etching of an n-type (100) silicon (Si) substrate under various condition. The PS was etched using hydrofluoric acid (HF) based solution and the porosity was optimized by introducing electroless chemical etching process prior to photo electrochemical (PEC) anodization. In the electroless etching, a delay time (T_D) of 2 min was applied. After that a cycle time (T) and pause time () of pulsed current were supplied throughout the 30 min PEC etching process. As grown Si and PS through conventional direct current (DC) anodization were also included for comparison. The result obtained showed that applying delay time helps to improve the uniformity and density of the porous structures. AFM indicated that the roughness of the Si increases as the dissolution of the Si occurred. Raman spectroscopy showed that an improvement in the crystalline quality of PS under pulse etching method compared to DC method indicated by the reduction of full width at half maximum (FWHM). A broad visible photoluminescence (PL) was observed from green to red with blue shift as nanocrystallite size decreases which constituted quantum confinement effect from the PS structures. Nickel (Ni) finger contact was deposited onto the PS to form metal semiconductor metal (MSM) photodetector. Ni/PS MSM photodetector by pulse method exhibited higher gain (2 times) compared to conventional Si device at 5 V bias.

Abstract: A single hybrid solar cell (SHSC) which consist of zinc oxide (ZnO) micro-rod and Poly (3-dodecylthiophene)(P3DDT) materials with nature dye from Melastoma malabathricum fruit (Mm) were fabricated to determine it electrical properties and power conversion efficiency (PCE). The ZnO microrod was growth by thermal method. P3DT was synthesis by oxidation polymerization method. Nature dye was extracted from Mm fruit in purplecolor.The fabrication of a SHSC started with growth ZnO microrodon the Indium Tin Oxide (ITO) in thin filmform, followed with P3DT layers and finally layered with Mm in 5 layers and 10 layers respectively.The SHSC wascharacterized the electrical conductivity and PCE also compared under dark condition and various light intensity. The conductivity of the samples is increase within the increment of light intensity and the efficiency of SHSC increase within the increment of layer of Mm. The highest electrical conductivity was for 10 layers of dye which is 2.678 + 0.002 Scm^-1. The power conversion efficiency (PCE) of the ITO/ZnO/P3DDT/10 layers dye achieved was the highest which is 0.0011% under radiation of 200 Wm^-2 intensity of light. As a conclusion, it can say that the amount of Mm can affect the performance of hybrid solar cell, where the dye is increased, the electrical conductivity and the PCE also increase. Thus, the Mm is a good dye and can be potential to apply in the solar cell.