New Ways to High-Quality Bulk Scandium Nitride

ScN was prepared in three different ways leading to single phase samples with low oxygen content in a broad range of particle sizes. Synthesis from the elements provides, in an exothermic reaction, brownish transparent single crystals (rock-salt structure type, space group Fm3m, a = 451.2(1) pm, Z = 4, Rint = 0.034, R1 = 0.013, wR2 = 0.018). From a decomposition reaction of Li3[ScN2] fine brown powders (particle size (almost equal)1 µm) were obtained. Via nitridation of intermetallic Sc-In phases even nanoscaled (<200 nm) ScN can be produced. The emerging In was converted to InI3 and removed at comparable low temperatures (Tmax = 453 K) by sublimation or extraction. Thermodynamic considerations enlighten the process. Crystal structure refinements, density measurements, and chemical analyses show an atomic ratio close to the ideal composition ScN with only a small vacancy concentration in the N-sublattice for all samples. Still, metal-like behavior in the electrical resistivity was observed (((rho)(300 K) - (rho)0 = 1.1 * 10^-4 (omega)cm, temperature coefficient 2.7 * 10^-3 K^-1). This interpretation is in accordance with the magnetic susceptibility (temperature-independent paramagnetism X0 (almost equal) 4 * 10^-6 emu/mol) and the observed band gap of (delta)E = 2.10(2) eV. The oxidation behavior dependence on the particle size is analyzed.