Super-pyroelectric effect in nanocrystalline films of BaTiO3 with macro-domain organization

Self-supported films of nanocrystalline BaTiO3 exhibit an earlier unreported phenomenon: orders of magnitude increase of pyroelectric effect (``super-pyroelectricity''). The measured value ($\sim $ 1$\mu $C/(cm2$\cdot $K)) is one the highest ever reported for ferroelectric materials. The super-pyroelectricity arises due to self-organization of hundreds of millions nanocrystalline ferroelectric grains in macro-domains: the regions where directions of the crystallographic axes are strongly correlated. Small temperature variations cause reversible changes in the direction of spontaneous polarization of ferroelectric grains in macro-domains producing gigantic pyroelectric current. In contrast to regular pyroelectricity observed in ferroelectrics, super-pyroelectric effect reaches maximum at 80-100 K below the temperature of the para-to-ferroelectric phase transition. This work demonstrates that polycrystalline macro-domains are capable of fast ($<$10 $\mu $sec!) and reversible adaptation to minute changes of external conditions, which promises creation of pyroelectric and piezoelectric devices with previously unattainable performance.