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β-Ga₂O₃ is a semiconductor material that has attracted much attention in power device applications due to its physical properties of an ultra-wide bandgap (4.9 eV) and high breakdown voltage (8 MV/cm). In this study, wesuccessfully prepared (001) β-Ga₂O₃ crystals doped with key impurities (including unintentional doping (UID)) such as Sn, Si, and Fe for n-type conductivity by using the EFG (Edge-defined Film-fed Growth) method. We conducted structural and optical characterization of β-Ga₂O₃ crystals doped with key impurities. XPS analysis indicated that characteristic peaks originating from Ga and O were commonly observed in all β-Ga₂O₃ crystals. The binding energy gradually decreased with the incorporation of dopants into the lattice. The Sn dopant was effectively employed and activated in the lattice of β-Ga₂O₃ crystals; however, Fe and Si dopants were barely incorporated into the lattice. XRD and Raman scattering analysis showed that the obtained β-Ga₂O₃ crystals had high crystal quality, and the crystal quality did not depend on different kinds of dopants. In UVF (UV fluorescence) measurements and RGB color analysis, UID, Si-, and Sn-doped Ga₂O₃ crystals showed intense blue luminescence; however, the Fe-doped Ga₂O₃ crystal showed pink luminescence. This trend was also observed from PL spectral analysis. UID, Si-, and Sn-doped Ga₂O₃ crystals show dominant blue (2.8~3.0 eV) and green luminescence (~2.4 eV, more dominant) originating from impurity levels of the donor-acceptor pair between O (donor) and Ga (acceptor) vacancies. This indicates that the luminescence between intrinsic impurity levels generated by the voids was not significantly affected by the dopant. However, Fe-doped in Ga₂O₃ crystals shows relatively intense red and IR region luminescence (consistent with the pink luminescence from UVF) with quenching of the green and blue luminescence. The PL quenching in the blue and green regions originated from the increase in non-radiative recombination due to the generation of trap states by the Fe dopant. In this study, we systematically analyzed the structural and optical properties of β-Ga₂O₃ crystals doped for n-type conductivity, and we look forward to the establishment of a series of nondestructive analytical echniques for the analysis of β-Ga₂O₃ crystals.

The microwave heating effect of SiC (silicon carbide) occurs at a specific frequency of 2.45 GHz. This investigation the microwave heating properties of SiC synthesized from composition modification polycarbosilane. Polycarbosilane powders were prepared by additive Zirconium and Titanium metallic precursors powder, followed by an investigation of their oxidation, curing, and thermal behaviors. The addition of metallic precursors effectively inhibited the formation of the amorphous phase and enhanced the growth rate of β-SiC crystal size. SiC prepared from pure polycarbosilane exhibited the highest temperature of 741ºC however, during a 60 minute thermal stability test, the temperature continuously decreased. On the other hand, the samples with metallic precursors displayed relatively lower peak heating temperatures but showed superior long term thermal retention.

In this study, we propose a method to enhance the oxygen evolution reaction (OER) catalytic performance by synthesizing a reduced graphene oxide (rGO) and cobalt-nickel layered double hydroxide (CoNi LDH) composite. WhileCoNi LDH exhibits high electrochemical activity, its low conductivity limits its catalytic efficiency. To overcome this limitation, rGO, which possesses high conductivity, was incorporated to improve electron transport and enhance thestructural stability of the catalyst. The rGO/CoNi LDH composite was synthesized via a hydrothermal method, and its structural and electrochemical properties were analyzed with varying rGO content. FE-SEM and EDS analyses confirmed the uniform dispersion of rGO within the composite structure of CoNi LDH. Electrochemical measurements, including LSV, Tafel analysis, and EIS, demonstrated that the optimal rGO content (10 mL) provided the lowest overpotential and highest electrical conductivity. These findings suggest a new approach for improving OER catalyst performance and contribute to the development of highly efficient electrochemical catalysts.