Efficient technology for manufacturing electrical ceramics from low-iron diopside rocks

Abstract

Relevance. The use of natural diopside CaMgSi2O6 in the production of ceramic dielectrics was implemented at two enterprises in the Chelyabinsk region in 1985 on the basis of comprehensive studies of diopside rocks of the Southern Baikal region by the team of the Department of Silicate Technology of Tomsk Polytechnic University. Natural diopside was used as an additive to the charge of electrical porcelain. In addition, ceramic dielectrics with a diopside crystalline phase were manufactured for exploitation at the frequencies of 106 Hz. Currently, the need for ceramic dielectrics in Russia is covered by imports. Though, the development of new technologies for ceramic dielectrics from domestic raw materials is relevant. Aim. To develop an efficient technology for ceramic dielectrics with a diopside crystalline phase from natural low-iron diopside rocks. This technology includes the production of compacts of unfired products by moulding aqueous suspensions of compositions of nonplastic components. Object. The technology of ceramic dielectrics with a diopside crystalline phase, including the firing of compacts formed from aqueous suspensions of diopside concentrate compositions with perlite as flux. Methods. The suspension was obtained by grinding the components in an aqueous environment in a ball mill with uralite balls at humidity of 20±2%. Compressive and bending strength, electrical strength, dielectric constant of the samples were determined according to the SS 24409-80, water absorption was measured according to the SS 26093-84. X-ray phase analysis was carried out on a DRON-3M diffractometer (Burevestnik, Russia), structure analysis was implemented on a JSM 6000 electron microscope (Jeol, Japan). Results. A distinctive feature of the proposed technology is the use of nonplastic components only to prepare the suspension and the exclusion of clay components. This makes it possible to reduce the humidity of the castings and stabilize the formation of the ceramic structure during firing. The authors have obtained ceramic dielectric with a diopside content of 70±2 wt % by firing products molded at 1130–1150°C. The bending strength reached 85–90 MPa with an electrical strength of 35–38 k V/mm2.

Keywords

• diopside
• perlite
• nonplastic components
• suspension
• ceramic dielectric