Role of charged defects on the electrical and electro-mechanical properties of rhombohedral Pb(Zr,Ti)O3 with oxygen octahedra tilts

TL;DR

This study investigates how charged oxygen vacancies and octahedral tilts influence the electrical and electro-mechanical properties of rhombohedral PZT ceramics, revealing that charged defects primarily cause domain-wall pinning and property degradation.

Contribution

It clarifies the role of charged defects versus octahedral tilts in domain-wall motion and dielectric/piezoelectric behavior in rhombohedral PZT ceramics, challenging previous assumptions.

Findings

Pinched hysteresis loops are linked to charged oxygen vacancies, not tilts.

Charged defects significantly affect permittivity and piezoelectric response at low frequencies.

Oxygen vacancy motion causes strong frequency dispersion in properties.

Abstract

Oxygen octahedra tilting is a common structural phenomenon in perovskites and has been subject of intensive studies, particularly in rhombohedral Pb(Zr,Ti)O3 (PZT). Early reports suggest that the tilted octahedra may strongly affect the domain switching behavior, dielectric and piezoelectric properties of PZT ceramics. In a way similar to that proposed for tilts, however, charged defects, associated with oxygen vacancies, may also inhibit the motion of the domain walls, resulting macroscopically in pinched hysteresis loops and reduced piezoelectric response. Here, we revisit the early studies on rhombohedral PZT ceramics with tilted octahedra by considering a possible role of both tilts and charged defects on domain-wall motion. We show that the observed pinched hysteresis loops are likely associated with the presence of defect complexes containing charged oxygen vacancies, and not tilts as suggested in some cases. Regardless of the presence or absence of long-range ordered tilts in rhombohedral PZT, the effect of charged defects is also prominent in weak-field permittivity and piezoelectric properties, particularly at sub-Hz driving conditions where the conductivity, related to the motion of oxygen vacancies, gives rise to strong frequency dispersion.