GaN crystals are synthesized by recrystallization technique in Na-Li-Ca alloy melt under different N₂ pressure. X-ray powder diffraction results confirm that the structure of crystals is GaN with wurtzite type and there still have raw powders remaining. The total mass of GaN decreases with the nitrogen pressure reduces. No GaN crystals are found in the solution under N₂ pressure of 0.4 MPa. The morphologies of the crystal are mainly prism and pyramid. The size of the crystal increases when closer to the liquid surface. Raman spectra indicates that these crystals are stress-free and crystal grown at 3.6 MPa has high structural quality or low impurity concentrations. The results reveal that the solubility and supersaturation of the solution are controlled by N₂ pressure. The principle of GaN crystal synthesis by recrystallization is discussed.

Rapid and accurate analysis of element concentrations in aluminum alloys is crucial due to their widespread use in modern industry. This paper proposes a one-point and multiline calibration fiber-optic laser-ablation spark-induced breakdown spectroscopy (OP-MLC FO-LA-SIBS) for the quantitative analysis of elements in aluminum alloys. The experimental system utilizes a compact fiber laser as the laser-ablation source and spark discharge to enhance the atomic emission. A portable multichannel fiber spectrometer is used to quickly collect spectra in the nongated mode. The concentrations of four elements (Mg, Cr, Cu, and Mn) in four aluminum alloy samples were calculated using the simple and efficient OP-MLC method, which involves taking another sample with a similar matrix as the standard sample. The average relative errors (AREs) for Mg, Cr, Cu, and Mn were 6.38%, 28.09%, 21.92%, and 18.97%, respectively. When the certified concentrations are greater than 0.02 wt.%, the ARE is only 13.04%. The OP-MLC FO-LA-SIBS system is compact, features simple spectra processing, and offers effective measurement, providing a convenient method for rapid and efficient quantitative analysis of elements in aluminum alloys in industrial production.