Development of crystallographic orientation during columnar structure growth in zirconia layers produced by electron beam physical vapor deposition

Crystallographic orientation of columnar structure in yttria-stabilized zirconia (YSZ) layers produced by electron beam physical vapor deposition (EB-PVD) is an important aspect to develop nanostructure-controlled thermal barrier coatings (TBCs). Several specimens were produced by EB-PVD on a rotating sample holder whose horizontal axis is normal to the vapor plume axis. The developments of the out-of-plane and in-plane Crystallographic orientations in the YSZ layers were investigated by using XRD pole figure analysis. 〈100〉-oriented columns were developed perpendicular to the YSZ layer/bond layer interface. This out-of-plane orientation rapidly grew and was completed in the early stage of the deposition. On the other hand, a twisted zone in which in-plane 〈100〉 direction differed at about 10° from the direction of the substrate rotation axis during deposition was formed up to 60 μm from the interface. Well-aligned in-plane 〈100〉 orientation along the substrate rotation axis was observed directly above the twisted zone. Processing parameters, such as substrate rotation speeds or deposition temperatures, affected the growth of the in-plane twisted zone. Raising the substrate rotation speed promoted the growth of the twisted zone and delayed the development of the in-plane orientation. In contrast, high deposition temperature accelerated the development of the in-plane orientation. Strain energy in the coating layer during deposition probably dominates the formation of the twisted zone.