Low-Temperature Phase Transformations ofPbZr1−xTixO3in the Morphotropic Phase-Boundary R

Abstract

We present anelastic and dielectric spectroscopy measurements of PbZr(1-x)Ti(x)O(3) with 0.455 < or = x < or = 0.53, which provide new information on the low-temperature phase transitions. The tetragonal-to-monoclinic transformation is first order for x < 0.48 and causes a softening of the polycrystal Young's modulus whose amplitude may exceed the one at the cubic-to-tetragonal transformation; this is explainable in terms of linear coupling between shear strain components and tilting angle of polarization in the monoclinic phase. The transition involving rotations of the octahedra below 200 K is visible both in the dielectric and anelastic losses, and it extends within the tetragonal phase, as predicted by recent first-principle calculations.

Elastic and anelastic relaxation behaviour of perovskite multiferroics I: PbZr0.53Ti0.47O3 (PZT)–PbFe0.5Nb0.5O3 (PFN)

“…There is a rounded minimum in the Young's and shear moduli at temperatures corresponding to the expected location of the tetragonal-monoclinic transition in PZT [49,[105][106][107][108][109]112]. The transition appears to be reversible for Pb ( [106,109].…”

“…The transition appears to be reversible for Pb ( [106,109]. If there is any associated anomaly in Q À1 , it is perhaps only a slight increase with falling temperature through the transition at both Hz and kHz frequencies [49,[105][106][107]109]. By way of contrast, a poled sample of Pb(Zr 0.52 Ti 0.48 )O 3 displayed a sharp minimum in the Young's modulus measured at *150 kHz [52,60,113,114].…”

“…A sample doped with Nb has also shown the same pattern of elastic softening [110]. Characteristic peaks in acoustic loss, expressed in terms of the inverse mechanical quality factor, Q À1 , show dispersion with respect to frequency and are attributed to the motion under stress of the ferroelastic twin walls [106,107,109,111]. From the measurements of Bourim et al [107] at Hz frequencies, it appears that the twin walls become pinned by oxygen vacancies in the vicinity of *400 K, below which the loss returns to low values.…”

“…The transition appears to be reversible for Pb ( [106,109]. If there is any associated anomaly in Q À1 , it is perhaps only a slight increase with falling temperature through the transition at both Hz and kHz frequencies [49,[105][106][107]109].…”

“…There are as yet no data for strain relaxation effects in PZT-PFN multiferroics, but lattice parameters and elasticity data from the literature for Pb ( Changes in elastic properties have been studied extensively for PZT [44,49,[105][106][107][108][109]. As expected for improper ferroelastic cubic-tetragonal and cubicrhombohedral transitions with strong coupling between symmetry breaking shear strains and the order parameter, measurements at Hz and kHz frequencies on ceramic samples with compositions close to the MPB show large (*50 %) softening of the Young's modulus, 1/S 11 , and shear modulus, G [44,[105][106][107]109]. A sample doped with Nb has also shown the same pattern of elastic softening [110].…”