Self-propagating, high-temperature combustion synthesis of rhombohedral AlPt thin films

Sputter-deposited, Al/Pt multilayer thin films of various designs exhibited rapid, self-propagating, high-temperature reactions. With reactant layers maintained at similar to 21 degrees C prior to ignition and films adhered to oxide-passivated silicon substrates, the propagation speeds varied from approximately 20 to 90 m/s depending on bilayer dimension and total film thickness. Contrary to current Al-Pt equilibrium phase diagrams, all multilayers reacted in air and in vacuum transformed into rhombohedral AlPt having a space group R-3(148). Rietveld refinement of AlPt powder (generated from thin film samples) yielded trigonal/hexagonal unit cell lattice parameters of a = 15.634(3) angstrom and c = 5.308(1) angstrom; the number of formula units = 39. Rhombohedral AlPt was stable to 550 degrees C with transformation to a cubic FeSi-type structure occurring above this temperature.