2021, Vol.31, No.3

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

Hexagonal shape Si crystals were grown by the mixed-source hydride vapor phase epitaxy (HVPE) method of mixing solid materials such as Si, Al and Ga. In the newly designed atmospheric pressure mixed-source HVPE method,nuclei are formed by the interaction between GaCln, AlCln and SiCln gases at a high temperature of 1200°C. In addition, it is designed to generate a precursor gas with a high partial pressure due to the rapid reaction of Si and HCl gas. The properties of hexagonal Si crystals were investigated through scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), high-resolution X-ray diffraction (HR-XRD), and Raman spectrum. From these results, it is expected to be applied as a new material in the Si industry.

Herein, a correlation between B-site cation order and spin-phonon coupling in La2NiMnO6 double perovskite hasbeen investigated. Raman spectra of La2NiMnO6 double perovskite annealed at 950 and 1400°C have been measured in the140-598 K range. A substantial softening of the phonon modes has been observed below the Curie temperature, whichemphasized the presence of the spin-phonon coupling in the system. The spin-phonon coupling was found to be stronger inrelatively more ordered La2NiMnO6 double perovskite. Thus, the magnitude of spin-phonon coupling was influenced by theNi/Mn cation order.

Diesel particulate filter (DPF) is a typical application field of cordierite (Mg2Al4Si5O18) honeycomb. Green body for DPF honeycomb was extruded using slurry paste and sintered at the temperature range of 980~1450°C. Quantitative crystal phase analysis was carried out by using Rietveld refinement method for powder XRD data. In conjunction with the quantitative Rietveld analysis, SEM-EDS analysis was carried for the crystal phases (indialite, cordierite, cristobalite,alumina, spinel, mullite, pro-enstatite). After removing amorphous phase on the sintered surfaces by chemical etching method, the shape and composition of the crystal phases can be clearly identified by SEM-EDS method. By combining the Rietveld refinement method and SEM-EDS analysis, crystal phase evolution process in DPF cordierite ceramics could be clarified. In addition, the coefficient of thermal expansion (CTE) of the DPF honeycombs were measured and compared with the calculated CTEs based on the quantitative crystal phase analysis results.