# Chemical Compensation Challenges in Processing Antiferroelectric PbZrO3 Thin Films

## TL;DR

This paper explores the challenges of processing PbZrO3 thin films, focusing on Pb loss during crystallization and its impact on material properties.

## Contribution

The study highlights the need for advanced characterization beyond X-ray diffraction to evaluate antiferroelectric films accurately.

## Key findings

- Pb loss during crystallization leads to off-stoichiometric outcomes and secondary phases in PbZrO3 thin films.
- X-ray diffraction alone cannot detect secondary phases like ZrOx, which affect polarization and phase transition properties.
- Voltage drops across ZrOx nanocrystals correlate with reduced polarization and increased phase transition fields.

## Abstract

The electric field-induced antipolar-to-polar phase transition
in antiferroelectric materials is accompanied by large changes in
the structural and functional response, making them attractive for
many applications ranging from pulsed energy capacitors to high-strain-high
(blocking-)­force actuators, solid-state heating and cooling systems,
and optoelectronic devices. PbZrO3, as an end member of
the PZT, (x)­PbZr1–x
Ti
x
O3, solid solution, has
been the subject of many studies. However, processing of perovskite
PbZrO3 is extremely challenging due to phase instabilities
induced by Pb loss at the temperatures necessary for perovskite crystallization.
Here, we discuss the challenges associated with Pb loss, as well as
its compensation through bulk Pb overstoichiometry and interfacial
PbO additions, in chemical solution processed, highly oriented PbZrO3 thin films. For both 042o- and 001o-oriented (o-orthorhombic distortion) PbZrO3 thin films, the crystallization interfaces are the most important
contributors to Pb loss and off-stoichiometric outcomes, and no single
approach was sufficient to address these challenges. Pb-rich and Pb-deficient
nonperovskite phases including ZrO
x
were
only observable through microscopic characterization, and X-ray diffraction
alone could not rule out the presence of such secondary phases. “Ideal”
macroscopic antiferroelectric polarization-electric field double hysteresis
curves were observed despite (at times) the large presence of secondary
phases. However, reduced saturation polarization and increased phase
transition electric fields were observed concomitantly with the presence
of secondary phase(s) and tentatively assigned to the voltage drop
across the ZrO
x
nanocrystals. Based on
these results, it is imperative that the presence of secondary phases
always be addressed (beyond X-ray diffraction spectra) in order to
correctly evaluate the properties of antiferroelectric films.