Composition controlled microstructure and mechanical properties of Yb/Lu co-doped SiAlON

► We sintered five Yb/Lu co-doped SiAlON ceramics with different Al/Si ratio. ► We studied the phase, microstructure and mechanical properties of the SiAlONs. ► The microstructure and properties could be tailored by the varied composition. ► Higher K 1c belonged to the samples with lower Al replacement. ► Higher hardness values were resulted from the samples having more α-SiAlON grains. A series of Yb 3+ and Lu 3+ co-doped SiAlON ceramics with different Al content were hot pressing sintered using same process. The phase composition, microstructure and mechanical properties of the sintered samples were studied to find the tailoring effects of composition variation on mechanical properties of SiAlON. The starting composition of the SiAlON ceramics was demonstrated to be effective in the final phase formation and the grain shape and size in the bulk. The grain morphology and grain boundary phase of the SiAlON ceramics thus prepared also played an important role in the mechanical properties of the Yb/Lu co-doped SiAlON. It has been found that the fracture toughness of the samples with a lower Al replacement and more elongated grains is higher, while the hardness values of the samples with more α-SiAlON grains and less grain boundary phase is higher.