Mn- α -SiAlON: A new member of α -SiAlON family

α-SiAlON, as solid solution of α-Si3N4, is a valuable ceramic material due to its excellent mechanical and functional properties. The structure of α-SiAlON is necessarily stabilized by so-called stabilizing cations. Up to now, various stabilizing cations including Li, Mg, Ca, Sr, and most rare earth elements have been used in α-SiAlON, but no α-SiAlON stabilized with transition metal cations has been reported. In this work, we report Mn-α-SiAlON as a new member of α-SiAlON family and, to the best of our knowledge, the first example of α-SiAlON stabilized with transition metal cations. Single-phase Mn-α-SiAlON with the nominal chemical composition of Mn0.75Si9.75Al2.25O0.75N15.25 was prepared by spark plasma sintering from precursor powder mixture of α-Si3N4, AlN, and MnO. The formation of Mn-α-SiAlON isostructural to α-Si3N4 was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The new Mn-α-SiAlON exhibited superior Vickers hardness of 23.1 GPa, good fracture toughness of 6.7 MPa·m1/2, and thermal conductivity of 7.60 W/(m·K). We hope that the discovery of Mn-α-SiAlON will open new possibilities for tailoring the chemical composition and optimizing the properties of α-SiAlON.