Movement of Pt markers in MgO during a solid-state reaction

The effectiveness of Pt in marking the initial location of heterophase boun daries between two reactants ina thin-film solid-state reaction is discusse d. The Pt markers were produced by dewetting a continuous Pt film at elevat ed temperatures, thus forming an array of small isolated particles. These p articles can then serve as fine-scale markers for tracking the motion of in terfaces. The thin-film diffusion couples with Pt markers were used, in thi s study, to investigate the effect of an applied electric field on a spinel -forming reaction. The reacted diffusion couples with Pt markers were analy sed using both transmission and scanning electron microscopy. Analysis of t he diffusion couples showed that the Pt markers could be affected by, or th emselves affect, the reaction process. The interface between the Pt marker and surrounding oxide matrix plays an important role in the reliability of Pt as an effective marker.