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

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 m^1/2 from 2.38 MPa m^1/2. Our achievement can be used as a reference to fabricate ZTM ceramics from coal gangue with high-value additions.