Microwave initiated solid-state metathesis routes to Li2SiN2

The fast ion conductor lithium silicon nitride, Li2SiN2, is produced in a metathesis reaction between silicon chloride, SiCl4, and lithium nitride, Li3N, initiated in a conventional microwave oven. Lithium amide, LiNH2, and ammonium chloride, NH4Cl, serve to control the temperature and enhance the yield of Li2SiN2. A reaction mechanism is proposed based on the exothermicity of forming the by-product salt lithium chloride with silicon nitride, Si3N4, as a likely intermediate. By varying the stoichiometry of the reactants the phase LiSi2N3 can also be produced. The Li2SiN2 product is characterized using powder X-ray diffraction, scanning electron microscopy and complex impedance spectroscopy. A pressed pellet of Li2SiN2 has a conductivity of 2.70 x 10(-3) S cm(-1) at 500 degrees C.