Composition-induced non-ergodic–ergodic transition and electrocaloric evolution in Pb(1−1.5x)La(x)Zr(0.8)Ti(0.2)O(3) relaxor ferroelectric ceramics

Abstract

Relaxor ferroelectrics, with polar nanoregions (PNRs), are good candidates for electrocaloric (EC) refrigeration. This study investigates the EC performance of the Pb(1−1.5x)La(x)Zr(0.8)Ti(0.2)O(3) relaxor ferroelectric ceramics by the direct measurement using a modified differential scanning calorimeter. All the ceramics exhibit pure perovskite phase with a dense microstructure. The results indicate that the increasing La substitution strengthens the relaxor behaviour, promotes the transition from non-ergodic to ergodic state, and enhances the thermal stability of EC property (instability η < 16% within 0–140°C for x = 0.09). While the EC peak widens and shifts to lower temperatures, the peak value decreases from ΔT(max) = 0.98 K (@140°C) for x = 0.06 to ΔT(max) = 0.25 K (@40°C) for x = 0.09 under an electric field of 40 kV/cm. Moreover, the ceramics with x = 0.07, near the non-ergodic–ergodic state boundary, show the optimised room temperature EC performance, i.e. ΔT = 0.41 K (@20°C) and η < 20% within a wide temperature range of 0–80°C. This work provides an effective material design approach for EC refrigeration in different application conditions.

Keywords

• differential scanning calorimetry
• thermal stability
• relaxor ferroelectrics
• ferroelectric transitions
• pyroelectricity
• lead compounds
• ferroelectric ceramics
• lanthanum compounds
• crystal microstructure
• electrocaloric (ec) refrigeration
• modified differential scanning calorimeter
• relaxor behaviour
• electrocaloric evolution
• relaxor ferroelectric ceramics
• composition-induced nonergodic-ergodic transition
• polar nanoregions
• perovskite phase
• dense microstructure
• la substitution
• thermal stability
• electric field
• nonergodic-ergodic state boundary
• temperature 0.0 degc to 140.0 degc
• pb(1-1.5x)la(x)zr(0.8)ti(0.2)o(3)