V.S.Konevsky, E.V.Krivonosov, L.A.Litvinov
Received December 26, 1997
Stress relaxation in ruby
crystals annealed at temperatures close to that of melting (Tm)
has been studied. The relaxation occurs mainly due to thermoactivated processes
during first few hours of the isothermal exposure. The residual stress
level depends on athermal phenomena of crystal structure defects relaxation
and can be lowered somewhat by a substantial elongation of the anneal duration.
As the annealing temperature is elevated from 0.95 Tm
to 0.995Tm , residual stresses and their nonuniformity over
the crystal length are reduced more than twice. The creep limit at 0.995Tm
has been determined to amount 1.52'0.075 MPa for ruby grown by Verneuil
technique.