On orientation relationships and morphologies of platinum precipitates in sapphire

Many technologies rely on the integrity of a bond between a metal and an oxide ceramic. The properties of the ceramic-metal interface influence the performance of engineering components, and failure at the interface can have serious consequences. Thus, the experimental determination of the properties of ceramic-metal interfaces is important in the field of materials science.;In this work, platinum precipitates were formed in sapphire substrates by high-energy implantation of platinum ions followed by thermal annealing. The crystallographic orientation relationships and the morphologies of the resulting precipitates were characterized using x-ray diffraction and transmission electron microscopy. The identification of energetically favorable precipitate orientation relationships, interfacial relationships, and precipitate morphologies were used to draw conclusions about the crystallographic dependence of interfacial energy in this model ceramic-metal system. Observations about the microstructural development of ion-implanted sapphire during annealing were also reported, including descriptions of the effects of transition aluminas on orientation relationships and the apparent stabilization of transition alumina by the presence of platinum precipitates.;The morphology of the precipitates in sapphire after annealing for 100 hours at 1600°C was determined. The morphology consists of both curved surfaces and planar interfaces. The planar interfaces include all sapphire orientations present in the experimentally-determined equilibrium shape of undoped sapphire and several that do not. The anneal time and temperature were estimated to be adequate for morphological equilibration to occur, but the precipitate morphologies did not converge on a single shape. The lack of full morphological equilibration is believed to be due to surface-attachment-limited kinetics. The morphology of platinum-containing cavities in sapphire after annealing at 1600°C was also determined. The sapphire surfaces are fully faceted and the facets coincide with those in undoped sapphire. The orientations and facets of the Pt-sapphire interfaces are the same as observed in precipitates in full contact with sapphire.;The identification of equilibrated morphologies and stable faceted interfacial orientations derived from this study supports future studies on mass transport along solid-solid ceramic-metal interfaces.