Characterization of the pyroelectric effect in ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$

Measurements of the pyroelectric effect in single crystals of ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ are reported as a function of doping, external electric field, and temperature. The pyroelectric response of the material is found to be accurately described theoretically. The sign pyroelectric voltage ${\mathbf{V}}_{\mathit{p}}$ can be switched by an external field. Although poling was possible to some extent, a permanent switching of the direction of polarization could not be achieved at room temperature. A sign reversal of ${\mathbf{V}}_{\mathit{p}}$ is observed as a result of thermal cycling, presumably due to activated domain rearrangement. The magnitude of the spontaneous polarization ${\mathbf{P}}_{\mathit{s}}$ is found to increase with doping in such a way that the product ρ${\mathbf{P}}_{\mathit{s}}$ remains approximately constant, where ρ is the resistivity. The origin of the polarization and the role of possible artifacts are discussed.