Field dependence of the electrocaloric effect in BaTiO3 and Ba(Zr0.12Ti0.88)O3: High-resolution measurements around the phase transition

The electric field dependence of the electrocaloric effect is investigated in BaTiO 3 and Ba(Zr 0.12Ti 0.88)O 3 by a direct method with sub-mK temperature resolution. The field dependence of the caloric temperature change Δ T ( E ) shows a pronounced change within a few Kelvin around the Curie temperature for the first-order phase transition in BaTiO 3. The transition from a linear field dependence in the ferroelectric phase over a butterfly-shaped to a quadratic field dependence in the paraelectric phase is compared to predictions of Landau–Devonshire theory. The simultaneous measurement of caloric and dielectric properties further allows for the investigation of the polarization dependence Δ T ( P ) of the electrocaloric effect. We find clear deviations from the predicted quadratic polarization dependence for temperatures close to the Curie temperature. Ba(Zr 0.12Ti 0.88)O 3 shows in contrast only a slow and gradual change of the field dependence over a broad temperature range as a consequence of its diffuse phase transition.