The sapphire （Al2O3） single crystal is a kind of excellent infrared transmission window materials. A large-sized sapphire （Ф225 mm×205 mm, 27.5 kg） was grown by SAPMAC method （sapphire growth technique with...The sapphire （Al2O3） single crystal is a kind of excellent infrared transmission window materials. A large-sized sapphire （Ф225 mm×205 mm, 27.5 kg） was grown by SAPMAC method （sapphire growth technique with micro-pulling and shoulder-expanding at cooled center）. Several kinds of inclusion in the large sapphire crystal were investigated by means of an optical microscopy （OM）, scanning electron microscopy （SEM） and electron probe microanalysis （EPMA）. The experimental results show that most inclusions are consisted of solid metallic and non-metallic particles as well as gas pores caused by the impurity of alumina as the raw material, the thermal dissociation of aluminum oxide melt and the reaction of the melt to the crucible material （Mo） at high temperatures. It is also found that in different crystal regions the inclusions are of varied sizes, morphology and chemical compositions. Finally, the measures to reduce and eliminate the inclusions are proposed to improve the crystal quality.展开更多
The professional modeling software package CrysVUn was employed to study the process of a large sapphire single crystal growth using Kyropoulos method.The influence of gas pressure on thermal field,solid-liquid interf...The professional modeling software package CrysVUn was employed to study the process of a large sapphire single crystal growth using Kyropoulos method.The influence of gas pressure on thermal field,solid-liquid interface shape,gas velocity field and von Mises stress were studied for the first time.It is found that the root of the seed melt when gas pressure equals to one atmosphere or more than one atmosphere,especially during the seeding period,this result is consistent with the experimental observation,and this paper presents three ways to solve this problem.The temperature gradient and stress decreases significantly as the gas pressure increases.The convexity of the solid-liquid interface slightly increases when the gas pressure increases.Numerical analysis was used to optimize the hot zone design.展开更多
The diameter of Czochralski (Cz) sapphire crystals is 50 mm. The sapphire substrates were lapped by using diamond powders and polished by chemical mechanical polishing(CMP) method using alkali slurry with SiO2 abrasiv...The diameter of Czochralski (Cz) sapphire crystals is 50 mm. The sapphire substrates were lapped by using diamond powders and polished by chemical mechanical polishing(CMP) method using alkali slurry with SiO2 abrasive. After obtaining the smooth surfaces, the chemical etching experiments were processed by using fused KOH and NaOH etchants at different temperature for different times. The dislocation was observed by means of optical microscope and scanning electron microscope. The clear and stable contrast images of sample etching pits were observed. On the whole, the dislocation density is about 104?105 cm?2. Comparing the results under the conditions of different etchants, temperatures and times during the etching proceeding, it was found that the optimal condition for dislocation displaying is etching 15 min with fused KOH at 290 ℃. At the same time, the formation of the etch pits and the reducing method of dislocation density were also discussed.展开更多
基金National Defensive Preliminary Research Funds of China (41312040404)
文摘The sapphire （Al2O3） single crystal is a kind of excellent infrared transmission window materials. A large-sized sapphire （Ф225 mm×205 mm, 27.5 kg） was grown by SAPMAC method （sapphire growth technique with micro-pulling and shoulder-expanding at cooled center）. Several kinds of inclusion in the large sapphire crystal were investigated by means of an optical microscopy （OM）, scanning electron microscopy （SEM） and electron probe microanalysis （EPMA）. The experimental results show that most inclusions are consisted of solid metallic and non-metallic particles as well as gas pores caused by the impurity of alumina as the raw material, the thermal dissociation of aluminum oxide melt and the reaction of the melt to the crucible material （Mo） at high temperatures. It is also found that in different crystal regions the inclusions are of varied sizes, morphology and chemical compositions. Finally, the measures to reduce and eliminate the inclusions are proposed to improve the crystal quality.
文摘The professional modeling software package CrysVUn was employed to study the process of a large sapphire single crystal growth using Kyropoulos method.The influence of gas pressure on thermal field,solid-liquid interface shape,gas velocity field and von Mises stress were studied for the first time.It is found that the root of the seed melt when gas pressure equals to one atmosphere or more than one atmosphere,especially during the seeding period,this result is consistent with the experimental observation,and this paper presents three ways to solve this problem.The temperature gradient and stress decreases significantly as the gas pressure increases.The convexity of the solid-liquid interface slightly increases when the gas pressure increases.Numerical analysis was used to optimize the hot zone design.
文摘泡生法生长蓝宝石单晶过程中,晶体常出现开裂、气泡等缺陷.本文通过Ansys有限元软件对热场结构和晶体生长过程进行数值模拟仿真,仿真分析结果表明热场隔热屏层数的多少直接影响热场温度梯度分布.为此,本文以仿真结果为基础,结合实际生产经验对单晶生长设备进行相应的热场改造,并进行单晶生长实验验证,验证结果显示改进设备生长蓝宝石单晶体位错密度均值减少76/cm2,掏棒长度均值增加118 mm.
基金Project(59772037) supported by the National Natural Science Foundation of China project(500016) supported by the Hebei Natural Science Foundation Project(20050080007) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘The diameter of Czochralski (Cz) sapphire crystals is 50 mm. The sapphire substrates were lapped by using diamond powders and polished by chemical mechanical polishing(CMP) method using alkali slurry with SiO2 abrasive. After obtaining the smooth surfaces, the chemical etching experiments were processed by using fused KOH and NaOH etchants at different temperature for different times. The dislocation was observed by means of optical microscope and scanning electron microscope. The clear and stable contrast images of sample etching pits were observed. On the whole, the dislocation density is about 104?105 cm?2. Comparing the results under the conditions of different etchants, temperatures and times during the etching proceeding, it was found that the optimal condition for dislocation displaying is etching 15 min with fused KOH at 290 ℃. At the same time, the formation of the etch pits and the reducing method of dislocation density were also discussed.
