High di-electric constant nano-structure ceramics synthesis using novel electric discharge assisted mechanical milling and magneto ball milling and its properties

Abstract

The conventional method to prepare functional oxides is ceramic-powder-based processing typically via solid-state reaction of microcrystalline starting powders at high temperatures. Disadvantages of this approach include the high temperatures of reaction, limited degree of product chemical homogeneity and difficulties in achieving rapid sintering. Various chemical-based processing routes have been developed to prepare powders of more homogeneous composition, improved reactivity and sintering ability at low temperatures. Regardless of the route chosen to synthesise complex oxides, almost all of them require lengthy heat treatment schedules that usually exceed 10 h, as well as multi-stage processing steps. We describe two approaches to address these problems, applied to successful synthesis of both MgAl 2 O 4 and CaCu 3 Ti 4 O 12 (CCT) oxides exhibiting excellent di-electric properties. One approach employed the novel direct synthesis technique of electric discharge assisted mechanical milling (EDAMM) and the second used the more conventional method of controlled ball milling using the magneto-mechanical method followed by heat treatment of nano-structural products. By using EDAMM, nano-crystalline precursors for transformation into high di-electric constant ceramics could be formed in as little as 0.1% of the processing time required for conventional solid-state techniques while ball milling using the magneto method also resulted in nano-structural precursors powders suitable for reaction by heat treatment to form oxide supercapacitor. Sample characterisation was carried out using XRD, TEM and SEM. Di-electric property measurements were performed using AC-LCR and by DC meters.