COMPATIBILITY BETWEEN MOLYBDENUM AND ALUMINUM NITRIDE

Molybdenum and aluminium nitride sintered discs are strongly bonded after hot pressing at 1850-degrees-C under 20 MPa in flowing argon. If aluminium nitride discs are pre-sintered with lime or yttria additive, the bonding is only achieved when the dopant content is weak (1 to 3%). By comparison with the behaviour of tungsten under the same conditions, the bonding is supposed to be due to the reaction of the secondary oxide phase of molybdenum with its analogue in aluminium nitride, providing a complex interfacial phase, able to exist at the grain boundaries of both the materials near the interface, and making the bonding strong after cooling. If the interfacial phase is too great in volume and too liquid (when AlN is doped with important amounts of lime or yttria) it is expelled from the interfacial zone and no bonding is observed.