On the presence of covalently bound phosphorus in amorphous Ni–Co–P and Fe–Co–P electroplates

Abstract It is shown (based on XRD patterns) that coatings electrodeposited from solutions containing cations of iron metal group [Ni(II) + Co(II) or Fe(II) + Co(II)] and hypophosphite anions are characterized by amorphous (or nanocrystalline) structure. EDX data testify that the obtained metal coatings contain substantial amounts of phosphorus. To identify the chemical state of phosphorus in these coatings, valence-to-core (vtc) X-ray emission spectroscopy (XES) method is used that allows to separate a presence in the prepared samples of elemental metal atoms and metal atoms covalently bound with metalloid atoms (P atoms in our case). Joint quantitative analysis of vtc XES and EDX data allows us to conclude that all phosphorus in the electrodeposited Ni–Co–P and Fe–Co–P coatings is covalently bound with metal atoms (as phosphide) and no elemental (or “free”) phosphorus is present in these coatings.