Preparation of fine oxide ceramic powders by freeze drying

The development of new methods for synthesis of advanced materials results in further improvement of their properties. In this paper freeze drying, a cryochemical method, is used for the synthesis of ZnO and Bi1.8Pb0.2Sr2Ca2C u3Ox powders. ZnO and Bi1.8Pb0.2Sr2Ca2Cu3Ox powders were derived from 1M so lution of Zn(NO3)(2)x6H(2)O, and 1M solutions of metal nitrates of Bi(NO3)( 3)x5H(2)O, Pb(NO3)(2), Sr(NO3)(2), Ca(NO3)(2)x4H(2)O and Cu(NO3)(2)x3H(2)O prepared with a 5% solution of HNO3, respectively. The aqueous solutions we re sprayed by a twin-fluid atomization system into liquid nitrogen and dehy drated by a freeze-dryer at -30 - 20 degreesC and reduced pressure of 13-20 Pa. X-ray powder diffraction and scanning electron microscopy characteriza tion are reported for the present powders.