α-SiAlON ceramics with elongated grain morphology using an alternative sintering additive

Abstract In this work, the use of a natural yttrium oxide and rare earth oxide solid solution (CRE 2 O 3 ) as stabilizers of the α-Si 3 N 4 phase to form α-SiAlON has been investigated. This oxide mix is produced at FAENQUIL-DEMAR, at a cost of only 20% of pure commercial Y 2 O 3 . Two α-SiAlONs using pure Y 2 O 3 or CRE 2 O 3 have been prepared, using mixes of 20% by volume of a molar fraction of 9:1 of AlN to Y 2 O 3 or AlN to CRE 2 O 3 , respectively, with 80% α-Si 3 N 4 . Samples were gas pressure-sintered at 1900 °C, under 1.5 MPa of N 2 for 60 min. Both compositions yielded α-SiAlON ceramics with high relative densities (98% t.d.), hardness of 18 GPa and fracture toughness of 5 MPa m 1/2 , with homogeneous microstructures composed of elongated α-SiAlON grains with aspect ratios of 5. It is concluded that the mixed rare earth concentrate (CRE 2 O 3 ) can be used to produce α-SiAlON ceramics with similar microstructures and mechanical properties of α-SiAlON ceramics fabricated using pure Y 2 O 3 , but with the advantage of its lower production cost.