Chemical factors governing the modification of layered phosphates by low-energy ion bombardment

Abstract

Mixed phosphate having layered structure of Zr phosphate matrix with intercalated alkali and transition metal cations have been bombarded with Ar + ions at energy of 2 keV and doses ranging between 10 15 and 10 17 ions/cm 2 . The general formulae of the studied systems are α-Zr(MPO 4 ) 2 (M=Li, Na, K and Cs) and a-ZrM(PO 4 ) 2 (M=Co, Ni, Cu and Sr). The modifications produced by the bombardment were studied by ESCA. According to the previous finding on acid Zr phosphates the main products of the bombardment are condensed polyphosphates and oxides. The M/Zr atomic ratio of the residue after ion bombardment does not depend upon the mass of the cation. Its modification is interpreted in terms of a recently proposed model involving a primary binary collision event followed by chemical reactions. The heat of formation of the formed products is shown to be an important driving force of these ion-induced chemical reactions.