首页|(162804)Static and dynamic strain relaxation associated with the paraelectric- antiferroelectric phase transition in PbZrO_3
(162804)Static and dynamic strain relaxation associated with the paraelectric- antiferroelectric phase transition in PbZrO_3
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NSTL
Elsevier
Order parameter coupling associated with the first order, improper ferroelastic (Pm3m - Pbam) transition at -510 K in PbZrO_3 has been analysed from the perspective of strain and elasticity. Formal treatment of spontaneous strains using lattice parameter data from the literature reveals typical coupling with the order parameter for octahedral tilting, Q_R, and stronger coupling with the order parameter for antiferroelectric displacements, QΣ. These indicate that coupling between the two order parameters via common strains is not only biquadratic, λQ_r~2Q_Σ~2, but may also have contributions from a higher order term, λQ_r~2Q_Σ~4- Variations of elastic and anelastic properties obtained by resonant ultrasound spectroscopy (RUS) at frequencies in the vicinity of 1 MHz show softening as the transition point is approached from above, discontinuous stiffening at the transition point and a pattern of further stiffening in the stability field of the orthorhombic structure. Below the transition point, the pattern of stiffening resembles the evolution of Q_R~2 and Q_Σ~2, as is typical of coupling dominated by terms with the form λe~2Q~2, where e is a spontaneous shear strain. The absence of softening due to terms of the form λeQ~2 implies that the relaxation time for changes in the order parameters in response to an induced shear strain is slower than ~10~(-6) s. Also in contrast with measurements from the literature made at lower frequencies, no evidence for mobility of ferroelastic domain walls was observed at RUS frequencies. A peak in acoustic loss observed at the transition point and precursor softening in the stability field of the cubic phase are consistent with evidence for local dynamical polar clusters. Apart from some differences in relaxation times, the antiferroelectric transition in PbZrO_3 does not appear to be overtly different from ferroelectric transitions such as occur in BaTiO_3.
NSTL
Elsevier
