Impurity-induced formation of Ti₁₋ₓZrₓB₂ solid solution ceramics during combined SHS-SPS sintering

Combination of self-propagating high-temperature synthesis (SHS) from Ti + B powder mixture followed by spark plasma sintering (SPS) is introduced for the fabrication of titanium diboride. Oxide impurities, including zirconium oxide and titanium oxide, are identified in the synthesized powders: the first one coming from the milling process after SHS to minimize agglomeration and the second one is a common oxide fine layer on particle surface. Both oxide phases are reduced during SPS treatment. Results confirm that increasing the SPS temperature enhances the reduction of ZrO₂, facilitating the incorporation of Zr cations into the lattice through substitution at Ti sites, thus allowing the formation of this solid solution diboride: Ti 1-x Zr x B 2 . The key finding is that the presence of a small amount of Zr cation, with higher atomic radius in TiB 2 crystal structure results in crystal distortion and it creates significant solid solution hardening effect as well as an improved wear response. • Monolithic titanium diboride is fabricated successfully through combination of SHS followed by SPS routes. • Borothermal reduction of oxide impurities in SHS-ed synthesized powder that are zirconium oxide and titanium oxide: The first oxide is a contamination from milling process after SHS and the second one is typical thin oxide layer on the surface of this boride ceramics. • Confirmation of oxides reduction by the careful Rietved analysis on XRD patterns and Zr cations are introduced into the lattice at a substitutional Ti position (increment of lattice parameter) and allows the formation of the solid solution diboride: creating hardening solid solution effect and improved wear response.