Effects of zirconium source and content on zirconia crystal form, microstructure and mechanical properties of ZTM ceramics

Abstract

ZTM ceramics were successfully derived from coal gangue. The effect of zirconium source (ZrO2 and ZrOCl2∙8H2O) and content on properties of the ZTM ceramics has been studied. The phase composition, density, and microscopic morphology were characterized with X-ray diffraction (XRD), Archimedes method and scanning electron microscopy (SEM). The influence of zirconium source, sintering temperature, zirconia content on flexural properties and fracture toughness was studied. The sample, with ZrOCl2∙8H2O added 12% zirconia (Z2TM12) sintered at 1475 °C for 3 h has the highest density of 2.83 g/cm3. Partially stable t-ZrO2 was present in samples with zirconium oxychloride (ZrOCl2∙8H2O) as the zirconium source, due to the constraints of mullite crystals. Therefore, Z2TM12 had both microcrack toughening and stress phase transformation toughening mechanisms. The flexural strength was increased from 162.40 MPa to 285.04 MPa, while the fracture toughness was improved to 3.55 MPa m1/2 from 2.38 MPa m1/2. Our achievement can be used as a reference to fabricate ZTM ceramics from coal gangue with high-value additions.