Electrocaloric properties of potassium tantalate niobate crystals

Abstract

The electrocaloric properties of potassium tantalate niobate (KTN) crystals were investigated by indirect estimation and direct measurement of temperature–electric field (T–E) hysteresis loops. The measured T–E loops showed a similar shape to strain–electric field (s–E) loops. The adiabatic temperature change ΔT due to the electrocaloric effect was estimated from the polarization change of this sample to be 0.49 K under a field of 20 kV/cm. The measured temperature change ΔT in these samples upon the release of the electric field from 20 kV/cm to zero was 0.42 K. The temperature dependences of the electromechanical and electrocaloric properties were measured. The maximum performance appeared at approximately the phase transition temperature of KTN crystal and the properties were relatively moderate-temperature-dependent.

Enhanced piezoelectric properties and electrocaloric effect in novel lead‐free (Bi0.5K0.5)TiO3‐La(Mg0.5Ti0.5)O3 ceramics

“…The parameter ξ is also utilized to evaluate the performance of different materials under the unit of electric field. The ξ of the ceramic with x = 0.01 approaches 0.3 K·mm/kV, which is competitive with the ECE efficiency of the other relaxor ferroelectric ceramics, as shown in Table . With respect to the ECE, aside from the polarization contribution, the diffuse phase transition and the existence of PNRs also play an important role in the temperature stability of the ECE.…”

“…The ξ of the ceramic with x = 0.01 approaches 0.3 KÁmm/kV, which is competitive with the ECE efficiency of the other relaxor ferroelectric ceramics, as shown in Table 1. [48][49][50][51][52][53] With respect to the ECE, aside from the polarization contribution, the diffuse phase transition and the existence of PNRs also play an important role in the temperature stability of the ECE. The alignment of the PNRs will be easily induced by the external electric field, which is beneficial for the enhancement of the ECE.…”

Electrocaloric properties of PZT- and BaTiO<inf>3</inf>- based ceramics and LiNbO<inf>3</inf> crystals

“…The dP/dT between 10 °C and 80 °C and estimated ¨T from Equation (1) for these ceramics are shown in Table 1. [18] Among these samples, it is estimated that the PZT ceramics with Tc of 140 C exhibited largest ΔT. [19] Considering that both ECE and field-induced displacement derive from the change in polarization, the similar appearance of the loops is reasonable.…”

Large Room Temperature Electrocaloric Effect in KTa1−xNbxO3 Single Crystal

“…A‐site doped with Li in KTN represents anti‐diffracting, which is attributed to both A‐site and B‐site ion‐disordered, and the coupling among them in KTN:Li . Recently, Maiwa reported that KTN:Li shows a large EC strength of Δ T = 0.42 K under E = 20 kV cm −1 near room temperature. But Li doping can obviously reduce the Nb content to remain the T c near room temperature, and induce distinctly different kind of polarization behavior …”