Graphene oxide (GO) based on coconut shell waste was successfully synthesized using a modified Hummers method, and the obtained GO was confirmed using XRD, FTIR, Raman spectroscopy, UV-Vis spectroscopy, and SEM-EDX. The XRD spectroscopy obtained the fractional content of the 2H graphite phase of 71.53%, 14.47% phosphorus, 10.02% calcium, and 3.97% potassium in coconut shell charcoal, where the GO sample tend to forms a phase of reduced graphene oxide (rGO). FTIR spectra shows compound functional groups of hydroxyl (- OH) at peak 1 (3449.92 cm −1 ), carboxyl (-COOH) at peak 2 (1719.42 cm −1 ) and peak 3 (1702.62 cm −1 ), and alcohol (C–OH) at peak 4 (1628.12 cm −1 ) and epoxy (CO) at peak 5 (1158.51 cm −1 ), which is similar to the GO synthesis from pure graphite. Raman spectroscopy analysis shows that the value of the I D /I G intensity ratio of the GO sample was 0.89 with a 2D single layer, and SEM results showed that surface morphology with an abundance of granular particles were found with different size distribution. The UV-visible results showed sufficient optical properties characterized by the spectrum, which formed because of the light absorption of the energy passed on the sample. The bandgap energy value of the sample obtained by the Tauc plot method was 4.38 eV, which indicates semiconductor properties.

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Abstract. The effects of molar ratios and sintering times on crystal structures and surface morphology on NdFeO3 oxide alloy have been studied. NdFeO3 oxide alloy formed by chemical preparation with solid reaction method using raw oxide Fe2O3 (99.9 %) and Nd2O3 (99.9 %) powders. In this article we reported the effects of molar ratios x = (-0.1, -0.2 and -0.3) and sintering times for 15 h and 20 h on crystal structures and surface morphology of Nd1+xFeO3 synthesized by solid-state reaction method. The results indicate that variation of molar ratio and sintering time has influenced the FWHM, crystalline size and grain size. The Nd1+xFeO3 have a major phase is NdFeO3, and other minor phases are Fe2O3, Nd2O3 and Nd(OH)3. The dominant intensity of hkl (121) with a value in FWHM, crystallite size, and grain size an indication the results will be applied as a gas sensor material as the focus of the further study.

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This research is aimed to study the effect of sintering temperature on crystalline structure and surface morphology of NdFeO3 oxide alloy materials. NdFeO3 was synthesized by solid state reaction method with mixing of 99.9% Nd2O3 and 99.9% Fe2O3 as precursors. Three samples with different process were made in this experiment. The 1st (#1) and 2nd (#2) samples were sintered for 84 hours at 950°C and 600°C. Calcination procces was carried out at 950°C for 50 hours. The 3rd (#3) sample was sintered for 84 hours at 600°C without calcination process. The samples were characterized by using SEM (Scanning Electron Microscopy) and XRD (X-Ray Diffraction). Based on the SEM characterization result, it was obtained that the sintering temperature influence on surface morphology of NdFeO3 grain size. The XRD analyze was obtained FWHM (Full Width at Half Maximum) value of sample #1, #2 and #3 are 0.11°, 0.10°, and 0.31°, respectively. The value of FWHM was associated with the peak at 2Θ of 32.53° for all sample, it is indicated of hkl (121). Further calculation based on crystallography data was carried out by rietveld method with rietica software and the best quality will be applied as a gas sensor materials.