A high-temperature oxidation-resistant diffusion barrier for PbZrxTi1−xO3 coating on nanocrystalline diamond film

A buffer layer for PbZrxTi1−xO3 (PZT) coating on nanocrystalline diamond (NCD) film was investigated to prevent the oxidation damage of NCD layer during ambient air annealing at high-temperature. As for the phase of buffer layer, metal nitride is more effective than pure metal for enhancing adhesion of PZT coating on NCD film. For the metal nitride-based buffer layer, the incorporation of Al and Si increases further the adhesive strength of PZT coating on NCD film. As a microstructural point of view, nanoscale multilayered structure was observed to contribute to the increase of adhesive strength between PZT and NCD. As a consequence, introducing thin (∼70 nm) composite buffer composed of Ti(Al)N/SiNx nanoscale multilayer with bilayer period of ∼5 nm as an intermediate layer between PZT coating and NCD film improved the high-temperature oxidation resistance of the NCD film and relevant adhesive strength of PZT coating even after the 900 °C air-annealing. The improved adhesion was attributed to the suppressed oxygen diffusion to the NCD film through the PZT layer at high temperature by the intervening nanoscale multilayer buffer.