Physico-mechanical properties and microstructure of multi-phase ceramic composites based on zircon and dolomite mixtures

Abstract

Four composites containing zircon and dolomite were designed by adding dolomite from 5wt% to 35wt% at the expense of zircon content. Densification parameters in terms of bulk density, apparent porosity and linear change were determined at different firing temperatures (1200°C–1400°C). Cold crushing strength of sintered composites, phase composition and microstructure were investigated. Samples contain 35wt% of dolomite and fired at 1200°C for 2 hours exhibited higher porosity (AP ∼ 51.25%) than other samples and can be used as porous ceramics. This is due to CO2 evaporation through the thermal decomposition of dolomite. Dense ceramics can be obtained by adding 5wt% of dolomite and fired at 1400°C for 2 hours (bulk density ∼3.67 g/cm3 and apparent porosity ∼4.5%). Only zirconia and diopside crystalline phases were detected at composite containing 35wt% of dolomite and fired at 1400°C. Due to the liquid phase sintering process, the densification parameters of the sintered samples have been enhanced by increasing the temperature. The mechanical properties of the sintered samples were improved due to the transformation toughening mechanism of tetragonal zirconia. Microstructure and EDAX analysis of the sintered composites show the presence of sub-prismatic zircon and rounded zirconia crystals as well as irregularly dark diopside crystals.