Domain-Wall Enhanced Pyroelectricity

Ferroelectric domain walls are not just static geometric boundaries between polarization domains; they are, in fact, dynamic and functional interfaces with the potential for diverse technological applications. While the roles of ferroelectric domain walls in dielectric and piezoelectric responses are better understood, their impact on pyroelectric response remains underexplored. Here, the pyroelectric response of (001)-, (101)-, and (111)-oriented epitaxial heterostructures of the tetragonal ferroelectric <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msub><a:mrow><a:mi>PbZr</a:mi></a:mrow><a:mrow><a:mn>0.2</a:mn></a:mrow></a:msub><a:msub><a:mrow><a:mi>Ti</a:mi></a:mrow><a:mrow><a:mn>0.8</a:mn></a:mrow></a:msub><a:msub><a:mrow><a:mi mathvariant="normal">O</a:mi></a:mrow><a:mrow><a:mn>3</a:mn></a:mrow></a:msub></a:mrow></a:math> is probed. These differently oriented heterostructures exhibit the same type of 90° ferroelastic domain walls, but their geometry and density vary with orientation. In turn, piezoresponse force microscopy and direct pyroelectric measurements reveal that (111)-oriented heterostructures exhibit both the highest density of domain walls and pyroelectric coefficients. By varying the thickness of these (111)-oriented heterostructures (from 100 to 280 nm), the density of domain walls can be varied, and a direct correlation between domain-wall density and pyroelectric coefficients is found. Molecular-dynamics simulations confirm these findings and reveal a novel domain-wall contribution to pyroelectric response in that the volume of the material in or near the domain walls exhibits a significantly higher pyroelectric coefficient as compared to the bulk of the domains. Analysis suggests that the domain-wall material has a higher responsivity of the polarization to both external fields and temperature. This study sheds light on the microscopic origin of domain-wall contributions to pyroelectricity and provides a pathway to controlling this effect.