Low-temperature synthesis of ceramics through unstable complexes

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The purpose of the present research was to establish the processes for the synthesis of double oxide ceramics at low temperatures, if possible at room temperature, through certain unstable complexes of ethlene glycole and hydrazine. The crystalline oxides were directly synthesized, not via hydroxide.ZnFe_20_4 with spinel structure was synthesized in the shape of balloon with thin wall by passing through the complexes of ethylene glycole. The balloons of Fe_20_3 were also prepared and converted to ZnFe_20_4 balloons with wavy-line texture by the solid-state reaction with ZnO.LiMn_20_4 spinel which was a candidate for cathode materials for lithium rechargeable batteries was prepared in a thin film at low temperature as 400ﾟC.Using hydrazine monohydrate, crystalline fine powder of ZnFe_20_4 was precipitated from aqeous solution near room temperature. Using ammonia, ZnFe_20_4 powder was also precipitated in a wide range of concentration of starting metal salts. In the case of hydrazine, it was necessary to limit the concentration of metal salts in a narrow range, in order to avoid the formation of hydrazine complexes and also of hydroxides. The precipitation conditions for the spinels, Fe_30_4 , NiFe_20_4 and CoFe_20_4, in crystalline powders were determined. These crystalline ferrites were found to be formed through corresponding green-rust structures.