Microwave-hydrothermal versus conventional hydrothermal preparation of Ni- and Zn-ferrite powders

Ni- and Zn-ferrite powders were prepared by a coprecipitation method in a microwave-hydrothermal (M-H) reaction. The formation conditions of the ferrite were determined in detail according to the reaction conditions (pH, temperature, and time) in this work. The phase identification, crystallinity, and morphology of the prepared samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The ferrite phase began to form at a relatively low temperature (120 degreesC) in a short-holding time (30 min) under the M-H process. The crystallization of single-phase ferrite was promoted with an increase of annealing temperature and time. In this work, we also compared the ferrite powder prepared by the M-H method with one prepared by the conventional hydrothermal method. Under the same conditions, the sample prepared by the conventional hydrothermal method did not show the ferrite phase in XRD pattern. (C) 2001 Elsevier Science B.V. All rights reserved.