Enhanced electrocaloric effect near polymorphic phase boundary in lead-free potassium sodium niobate ceramics

Xiangjian Wang , Jiagang Wu (1) , Brahim Dkhil (2) , Baixiang Xu (3) , Xiaopeng Wang (1) , Guohua Dong (4) , Guang Yang (4) , Xiaojie Lou

1 department of Materials Science
2 SPMS - Laboratoire Structures, Propriétés et Modélisation des solides
3 Institute of Materials Science, Technische Universitat
4 Electronic Materials Research Laboratory

The electrocaloric (EC) effect in lead-free (1-x)(K0.48Na0.52)(Nb0.95Sb0.05)O3-xBi0.5(Na0.82K0.18)0.5ZrO3 ceramics was investigated using an indirect thermodynamic method. Large EC temperature changes were obtained in the vicinity of a polymorphic phase boundary at 40 kV/cm, e.g., 0.32 K at 359 K for x = 0.03, 0.51 K at 350 K for x = 0.04, and 0.48 K at 300 K for x = 0.05, respectively. These values are larger than the previous results at inter-ferroelectric phase transition and, more interestingly, are found to be comparable to those usually explored at the Curie temperature. The operational temperature window is broad near the polymorphic phase boundary due to the diffuseness of the phase transition. The enhanced electrocaloric effect is attributed to the formation of nanodomains near the polymorphic phase boundary, which reduces domain wall energy and facilitates the polarization rotation. The construction of a polymorphic phase boundary and the arrangement of coexisting phases at the nanoscale may open a promising route to explore EC materials. © 2017 Author(s).

Keywords: Diffuseness of the phase transition; Electro-caloric effects; Ferroelectric phase transition; Operational temperature; Polarization rotation; Potassium sodium niobate; Temperature changes; Thermodynamic methods; Phase transitions; Ceramic materials; Ferroelectric ceramics; Ferroelectric materials; Phase boundaries; Pyroelectricity; Sodium; Temperature

Domains: Materials

Xiangjian Wang, Jiagang Wu, Brahim Dkhil, Baixiang Xu, Xiaopeng Wang, et al.. Enhanced electrocaloric effect near polymorphic phase boundary in lead-free potassium sodium niobate ceramics. Applied Physics Letters, 2017, 110 (6), pp.063904. ⟨10.1063/1.4976026⟩. ⟨hal-02317037⟩