Abstract: a-Al₂O₃ powders and aluminaceramic were prepared by high pure AlOOH as the precursor material. Effects of NH₄F or AlF₃ on the transformation and microstructure of the a-Al₂O₃ powders and ceramic were investigated by scanning electron microscopy, X-ray diffraction, X-ray fluorescence and X-ray photoelectron. The results show that the introduction of NH₄F or AlF₃ promotes the morphology of α-Al₂O₃ to change from particle-like to plate-like shape. However, the α-Al₂O₃ platelets will revert to grains again after calcinated at high temperature. The plate-like α-Al₂O₃ can maintain the disk shape after calcinated at 1300℃, when the α-Al₂O₃ powders are pressed into disk under different pressure. The morphology of α-Al₂O₃ crystals changes from platelet to polygonal when they are further sintered up to 1600℃. However, under hot pressing condition, the platelet α-Al₂O₃ crystals don't show the polygonal morphology. The densification of α-Al₂O₃ ceramic is strengthened and the relative density of the ceramics increases from 77.6% to 92.2%with the rise of the sintering temperature. The density of α-Al₂O₃ ceramic prepared with particle-shaped powders is larger, compared to that prepared with plate-like powders, which increases from 92.2% to 93.0% after sintered at 1600℃.

Key words: alumina, microstructure, sintering, powder, fluorides

摘要： 以高纯氢氧化铝为主要原料，利用扫描电子显微镜、X射线衍射、X射线荧光光谱及X射线光电子能谱等技术，研究了引入NH₄F或AlF₃对α-Al₂O₃转变特征、氧化铝粉体及陶瓷显微结构的影响。结果表明：引入NH₄F或AlF₃促进α-Al₂O₃晶体形貌由颗粒状向片状转变。但是经高温煅烧，形成的片状α-Al₂O₃晶体又转变为颗粒状晶粒。粉体经不同压力成型后的块状样品，在1300℃煅烧后，α-Al₂O₃晶体仍保留片状形态。但是进一步升温到1600℃烧结的氧化铝陶瓷，晶体形貌由片状逐渐转变为多面体。热压条件下，氧化铝陶瓷晶体仍能够保持片状，没有出现多面体形态。随着烧结温度的提高，样品烧结致密化程度不断增大，相对密度从77.6%增加到92.2%。相比以片状粉体为原料烧结的α-Al₂O₃陶瓷，以颗粒状粉体为原料烧结的陶瓷相对密度要大，在1600℃烧结的α-Al₂O₃陶瓷密度从92.2%提高到93.0%。

关键词: 氧化铝, 显微结构, 烧结, 粉体, 氟化物