ROLE OF OXYGEN IN MICROSTRUCTURE DEVELOPMENT AT SOLID-STATE DIFFUSION-BONDED CU ALPHA-AL2O3 INTERFACES/

Microstructure development at solid-state diffusion-bonded Cu/alpha-Al 2O3 interfaces has been studied using optical and electron microscopy. High-purity Cu foil was bonded between basal-oriented alpha-Al2O3 sin gle-crystal plates at 1040-degrees-C for 24 h in a vacuum of approxima tely 1.3 X 10(-4) Pa (1 X 10(-6) torr). Optical microscopy of as-bonde d specimens revealed a large Cu grain size, fine pores, and long needl es of Cu2O at the interface. Bulk specimens were annealed at 1000-degr ees-C for various times under controlled oxygen partial pressures in C O/CO2 mixtures. Consistent with a thermochemical analysis, CuAlO2 coul d be formed at the interfaces. The CuAlO2 was acicular and discontinuo us, but occurred in a uniform distribution over the bulk specimen inte rfaces.