Abstract
This paper reports a method for producing α-Al2O3 at low temperature, which uses a seeding technique. White precipitate of aluminum hydroxide, which was prepared with a homogeneous precipitation method using aluminum nitrate and urea in aqueous solution, was peptized by using acetic acid at room temperature and then transformed to a transparent alumina sol. To the alumina sol α-Al2O3 particles were added as a seed, and then the sol containing α-Al2O3 particles was transformed to an α-Al2O3-seeded alumina gel by drying the sol at room temperature. The nonseeded alumina gel was amorphous or fine crystallites even after being annealed at 600°C and was crystallized to γ-Al2O3 at 700°C. The α-Al2O3 seeding promoted crystallization of alumina gel to α-Al2O3. The promotion of crystallization was made remarkable with a decrease in α-Al2O3 particle size and an increase in α-Al2O3 particle content in weight for the final seeded alumina gel. With an α-Al2O3 particle size of 150 nm and an α-Al2O3 particle content of 5%, the seeded alumina gel was partially crystallized to α-Al2O3 by annealing at a temperature as low as 700°C and mostly at 900°C.
Highlights
Electroconductive materials such as gold, silver, and copper and electric-insulating materials are quite essential for producing electronic devices such as integrated circuits [1,2,3]
Alumina is one of representative electricinsulating materials. Since it has high thermal conductivity and high chemical stability at high temperature compared to other electro-insulating materials such as glass, plastic, and paper [4,5,6], it is promising as the electric-insulating material used in the electronic devices
The inductively coupled plasma (ICP) measurement showed that an Al concentration in the sol was 0.717 M, which indicated that 71.0% of the Al(NO3)3 was transformed to the alumina sol
Summary
Electroconductive materials such as gold, silver, and copper and electric-insulating materials are quite essential for producing electronic devices such as integrated circuits [1,2,3]. Alumina is one of representative electricinsulating materials Since it has high thermal conductivity and high chemical stability at high temperature compared to other electro-insulating materials such as glass, plastic, and paper [4,5,6], it is promising as the electric-insulating material used in the electronic devices. The α-alumina can be produced by fabricating amorphous alumina with methods using liquid phase such as precipitation and sol-gel process and annealing it at high temperature [11,12,13]. These methods need the high temperatures, which brings about much consumption of energy. Low temperature processes for producing α-alumina are desired for saving energy
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