%0 Journal Article
%T Low Temperature Synthesis of ¦Á-Alumina with a Seeding Technique
%A Kazuhiro Inoue
%A Masachika Hama
%A Yoshio Kobayashi
%A Yusuke Yasuda
%A Toshiaki Morita
%J ISRN Ceramics
%D 2013
%R 10.1155/2013/317830
%X This paper reports a method for producing ¦Á-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 ¦Á-Al2O3 particles were added as a seed, and then the sol containing ¦Á-Al2O3 particles was transformed to an ¦Á-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¡ãC and was crystallized to ¦Ã-Al2O3 at 700¡ãC. The ¦Á-Al2O3 seeding promoted crystallization of alumina gel to ¦Á-Al2O3. The promotion of crystallization was made remarkable with a decrease in ¦Á-Al2O3 particle size and an increase in ¦Á-Al2O3 particle content in weight for the final seeded alumina gel. With an ¦Á-Al2O3 particle size of 150£¿nm and an ¦Á-Al2O3 particle content of 5%, the seeded alumina gel was partially crystallized to ¦Á-Al2O3 by annealing at a temperature as low as 700¡ãC and mostly at 900¡ãC. 1. Introduction Not only electroconductive materials such as gold, silver, and copper but also electric-insulating materials are quite essential for producing electronic devices such as integrated circuits [1¨C3]. Alumina is one of representative electric-insulating 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¨C6], it is promising as the electric-insulating material used in the electronic devices. There are various crystal structures in the alumina. Among the various crystal structures, alumina that reveals electric insulation is of ¦Á type. The ¦Á-alumina has been conventionally produced by annealing aluminum hydroxide derived from aluminum salts or minerals at temperatures higher than 1000¡ãC [7¨C10]. The ¦Á-alumina can be also produced by fabricating amorphous alumina with methods using liquid phase such as precipitation and sol-gel process and then annealing it at high temperature [11¨C13]. These methods need the high temperatures, which brings about much consumption of energy. Accordingly, low temperature processes for producing ¦Á-alumina are desired for saving energy. Our research group has studied effects of nanocrystallites seeding on various titanates such as PZT and BST fabricated by the sol-gel method for the last decade [14¨C17]. As a result, their crystallization temperatures were
%U http://www.hindawi.com/journals/isrn.ceramics/2013/317830/