Investigation on AlN Crystal Synthesis with Aluminum Metal and Mineralizer by Ammonothermal Method

• Main Authors: Chun-Chiang Huang, 黃俊強
• Other Authors: Yu-Shiang Wu
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/66627405950514958930

碩士 === 中華技術學院 === 機電光工程研究所碩士班 === 96 === AlN crystals were prepared utilizing an ammonothermal method under conditions of high temperature and pressure. The effects of temperature and mineralizers on AlN crystal synthesis and structure were investigated. Al powder and mineralizer reactants were placed in an autoclave and reacted with liquid ammonia under conditions of high temperature and pressure、producing a supercritical fluid which resulted in the formation of AlN crystals. AlN crystals were synthesized with a 1:1 mole ratio of aluminum metal to mineralizer and crystal growth temperature was varied from 300-500°C. The structural and physical properties of AlN crystals were examined via scanning electronic microscope (SEM)、transmission electronic microscope (TEM)、and powder X-ray diffraction (XRD). The SEM micrographs indicate irregular crystal shape. The particles synthesized under 500°C with NH4I and NH4Br mineralizers were roughly oblong in shape and had diameters of approximately 100 nm and 125 nm、respectively. Furthermore、as verified by SEM、the AlN crystals had hexagonal structures for all parameters tested. XRD patterns revealed that AlN crystals could not be formed at 300 and 400℃ when NH4Cl and NH4Br mineralizers were utilized. However、at 500℃、AlN crystals were synthesized utilizing NH4Br as the mineralizer. Unlike NN4Br and NH4Cl、when NH4I was utilized as the mineralizer、AlN crystals were synthesized at temperatures as low as 300℃. As determined by the Rietveld method、the AlN synthesized from NH4I exhibits other impurities in comparison with the standard hexagonal AlN. As temperature increased、the growth rate of AlN crystals increased for the NH4Br and NH4I mineralizers. Thus、one can determine that the amount and variety of mineralizers will directly affect the synthesis and the properties of AlN crystals.