Charge migration in Pb(Zr,Ti)O3 ceramics and its relation to ageing, hardening, and softening

Abstract

The dielectric response of hard (Fe-doped) and soft (Nb-doped) rhombohedral Pb(Zr 0.58 Ti 0.42 ) 1-x Me x O 3 (PZT; Me= Fe or Nb) ceramics was studied at subswitching conditions over a wide range of temperatures (50°C to 450 °C) and frequencies (10 mHz to 10 kHz). The results show qualitative differences in behavior of the acceptor and donor doped samples. Hard materials exhibit a steep increase of the complex permittivity with decreasing frequency. The onset of the dispersion is thermally activated with activation energy of about 0.6-0.8 eV and is attributed here to oxygen vacancy hopping. Activation energy for ac conductivity observed in soft materials is estimated to about 1.7 eV, corresponding to the half of the energy gap of Pb(Zr,Ti)O 3 and is thus consistent with electronic conduction. The relevance of ionic hopping conductivity in hard materials to ferroelectric aging / deaging and hardening is analyzed. Strongionic conductivity in hard and its absence in soft samples agree well with the dipolar mechanism of ageing in hard materials and the absence of significant ageing in soft materials.

Temperature dependent piezoelectric response and strain–electric-field hysteresis of rare-earth modified bismuth ferrite ceramics

“…Additional factors that can influence the S-E hysteresis of RE-BFO may be, for example, the movement of pinning centers such as charged defects during electric-field cycling 58,59 , causing internal bias fields [52][53][54][55] that can influence strain. C. High temperature piezoelectric functionality The piezoelectric coefficient (d 33 ) of the three ceramics was first evaluated as a function of the poling-electric-field (Fig.…”

Electrical conductivity and thermopower of (1 − x) BiFeO3– xBi0.5K0.5TiO3(x = 0.1, 0.2) ceramics near the ferroelectric to paraelectric phase transition

“…The figure shows the reversible response going from p-type (in O 2 ) via n-type (in N 2 ) and back to p-type (in synthetic air) semiconductor behaviour. The hardness of ferroelectric PZT can be tuned by acceptor and donor substitution, 48,49 and the hardening of acceptor substituted PZT has been explained by defect ordering due to rearrangement of oxygen vacancies. 50 Such ordering has also been studied in e.g.…”

Antiferroelectric-like properties and enhanced polarization of Cu-doped K0.5Na0.5NbO3 piezoelectric ceramics

“…Recent studies revealed that more than one process of aging may be active in one material. 8,9 Since the volume effect is related to the migration of charged carriers, both the thermodynamic and kinetic behaviors of these carriers should be considered. The crucial role played by the migration kinetics of point defects has been demonstrated in Al 3þ -doped BaTiO 3 ceramics, 10 where the Al 3þ -doping leads to lattice shrinkage and suppresses the FE aging effect at high level doping.…”