Research Of Preparation Of α-Al₂O₃ Powder By Sol-Gel Method

With the advent of 5G era,the demand of high purityα-Al₂O₃ ceramics in the circuit substrate and electrode co-firing is increasing day by day.The preparation temperature ofα-Al₂O₃ powder is very high,generally above 1100℃,which will cause the agglomeration of the powder.The agglomeration reduces the sintering activity of the powder,and makes the sintering temperature ofα-Al₂O₃ ceramics very high.So it is very important to lower the synthesis temperature ofα-Al₂O₃ powder.In this paper,α-Al₂O₃ powder is prepared through sol-gel method by using different aluminum sources and ammonia as raw materials.The effects ofα-Al₂O₃ seed,Al F₃,aging time,ball mill and drying methods on the preparation temperature ofα-Al₂O₃ powder were studied.The influnce of different ball milling methods on particle size distribution and sintering properties ofα-Al₂O₃ powder were investigated.X-ray diffraction（XRD）,infrared absorption spectroscopy（FT-IR）,thermogravimetric-differential scanning calorimetry（TG-DSC）,scanning electron microscope（SEM）and solid-state nuclear magnetic resonance（NMR）were used to characterize precursor,α-Al₂O₃ powders and ceramics.The main research results are as follows:（1）Due toα-Al₂O₃ seeds and Al F₃mineralizer treatment,preparation temperature ofα-Al₂O₃ powder was lowered by about 150°C.Precursor was dried by ordinary drying box,then milled and preheated at 400°C,α-Al₂O₃ powder with an alpha phase of 99%can be obtained by calcining at 925℃for 15min.The powder by cacining precursor at 1050℃for2h was grinded by planetary ball mill,the ceramic sintered at 1400℃only reached the maximum relative density of 88%.The powder by cacining precursor at 925℃for 1h was grinded by stirring mill,the ceramic sintered at 1550℃reached the maximum relative density of 95%.（2）α-Al₂O₃ powder with an alpha phase of 98%can be obtained by calcining precursor which was dried by freeze drying method at 975℃for 2h.Precursor was dried by freeze drying,then milled and preheated at 400°C,α-Al₂O₃ powder with an alpha phase of 98%can be obtained by calcining at 850℃for 15min.The powder by calcining precursor at 975℃for 2h was grinded by planetary ball mill,the ceramic sintered at1400℃reached the maximum relative density of 94%.The powder by calcining precursor at 850℃for 1h was grinded by stirring mill,the ceramic sintered at 1550℃reached the maximum relative density of 94%.（3）α-Al₂O₃ powder with an alpha phase of 98%can be obtained by calcining precursor which was dried by microwave drying method at 975℃/2h.Precursor was dried by microwave drying,then milled,α-Al₂O₃ powder with an alpha phase of 97%can be obtained by calcining at 850℃for 15min.The powder by calcining precursor at 975℃for2h was grinded by planetary ball mill,the ceramic sintered at 1400℃reached the maximum relative density of 92%.The powder by calcining precursor at 850℃for 1h was grinded by stirring mill,the ceramic sintered at 1550℃reached the maximum relative density of 97%.