Abstract
Measurements have been made of the transit times τ of pulses of 30 MHz longitudinal and transverse ultrasonic waves in PbF 2 at room temperature using hydrostatic pressures up to where the irreversible cubic-to-orthorthombic transformation occurs (near 4 kbar). Above 3 kbar 1/τ no longer increased linearly with pressure and exhibited some time dependence at fixed pressures before echo disappearance. The elastic stiffness moduli showed no significant softening before the transformation began. Length, mass density, and X-ray measurements on samples after they had been returned to 1 bar confirmed that milky white regions in them were orthorhombic but filled with defects.
Published Version
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