Structural transitions at the nanoscale: the example of palladium phosphides synthesized from white phosphorus

International audienceStoichiometric reactions of Pd(0) nanoparticles with various amounts of white phosphorus (P-4) are an efficient route to convert them into the corresponding Pd phosphides PdxPy. Formation of crystallized palladium phosphide nanoparticles is a two-step process, which allows exploring in detail the phase transitions of the PdxPy system, from amorphous Pd-P nanoparticles (formed in a first step at moderate temperature) to crystallization (at higher temperature). The second temperature was found to be strongly dependent on the Pd/P ratio: PdP2, Pd5P2 and Pd3P stoichiometries form the amorphous phases, but only PdP2 and Pd5P2 could be further crystallized from them. Although it exists as a bulk crystalline material, Pd3P could only be crystallized by starting from the more Pd-rich Pd6P composition. Phase-to-phase transformations from P-poor phosphides (Pd3P and Pd5P2) to the P-rich PdP2 were also demonstrated, and a first Pd-P phase diagram at the nanoscale was tentatively produced