The high temperature creep behavior of polycrystalline strontium zirconate.

The high temperature creep behavior of polycrystallihe SrZrC^ is investigated.Creep specimens were prepared from sintered powder compacts containing Fe2 0 3 additions of 0.85 wt.$ and 1.35 wt.$ to accelerate sintering and densification.A high temperature x-ray investigation showed no change in the structure of SrZrOg over the temperature range 25°C to 1300°C.Specimens varying in grain size from 0.45 ym to 2.04 um were creep tested in air between 1160°C and 1350°C at stresses of 1000 psi to 4000 psi under four-point, dead load conditions.Only the specimens containing 1.35 wt.% Fe2 0 3 sintered to near theoretical density (99$) and exhibited a relatively stable creep behavior from which the various creep parameters were deter mined.An activation energy of 169tl0 kcal/mole, and a dependence of creep rate upon the stress cubed and o 2 reciprocal of the grain size, i.e., C ^O v d , was determined for the creep process in SrZr0 3 .This is consistent with the nonviscous creep model developed by Weertman and modified by Garofalo for grain size effects, in which the controlling mechanism is dislo cation generation and climb.It is proposed that deformation occurs in SrZrC^ principally through mecha nical twinning, which Cottrell and Bilby show to be a dislocation mechanism.