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

α-SiAlON, as a 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. To date, 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 the 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 a nominal chemical composition of Mn_0.75Si_9.75Al_2.25O_0.75N_15.25 was prepared by spark plasma sintering from a precursor powder mixture of α-Si₃N_4, 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 a superior Vickers hardness of 23.1 GPa, good fracture toughness of 6.7 MPa·m^1/2, 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.