Thermally induced stress and strain in YAG/sapphire single crystal composites

摘要

The thermally induced stress of the order of 200 Mpa and strain of the order of 2 x 10~(-4) inadhesive free bonded (AFB®) YAG/sapphire single crystal composites have been determined asfunctions of crystallographic orientation by stress birefringence measurements using apolariscope and by surface figure measurements using a phase shift Fizeau interferometer,respectively. The deformation of YAG or sapphire end faces of the composite samples intoanticlastic surfaces is likely due to thermally induced relative biaxial strain between the YAG andsapphire components during heat-treatment.We have found that the YAG/sapphire composites stay stress- and strain-free when they are heattreatedbelow a critical temperature. The thermally induced stress and strain increaseexponentially with respect to the heat-treat temperature that is above a critical temperature.