Trirelaxor Ferroelectric Material with Giant Dielectric Permittivity over a Wide Temperature Range

Abstract

Advanced ferroelectrics with a combination of large dielectric response and good temperature stability are crucial for many technologically important electronic devices and electrical storage/power equipment. However, the two key factors usually do not go hand in hand, and achieving high permittivity is normally at the expense of sacrificing temperature stability. This trade-off relation is eased but not fundamentally remedied using relaxor-type materials which are known to have a diffuse permittivity peak at their relaxor transition temperatures. Here, we report an anomalous trirelaxor phenomenon in a barium titanate system and show that it can lead to a giant dielectric permittivity (εr ≈ 18 000) over a wide temperature range (T span ≈ 34K), which successfully overcomes a long-standing permittivity–stability trade-off. Moreover, the enhancement in the dielectric properties also yields a desired temperature-insensitive electrocaloric performance for the trirelaxor ferroelectrics. Microstructure characterization and phase-field simulations reveal a mixture of tetragonal, orthorhombic, and rhombohedral polar nanoregions over a broad temperature window in trirelaxor ferroelectrics, which is responsible for this combination of giant dielectric permittivity and good temperature stability. This finding provides an effective approach in designing advanced ferroelectrics with high performance and thermal stability.

Feasible Way to Achieve Multifunctional (K, Na)NbO3-Based Ceramics: Controlling Long-Range Ferroelectric Ordering

“…Note that much better Sig and R w values are observed for x = 0.10 using an R–O–T phase model that those observed using a pure cubic phase (Table S1), illustrating the existing local polar symmetries inside the macroscopic pseudo-cubic symmetry, which is further confirmed by the well-fitted results of the phase fraction (Figure g). Similar phenomena were also observed in other lead-free piezoceramics. − In addition, O and T phases almost equally share the phase fraction at x = 0, which is consistent with the similar intensities of (002) pc and (200) pc peaks (Figure g). The fraction of the T phase increases a little at x = 0.02 due to the slightly decreased T O–T .…”

High‐Performance Electrostrictive Relaxors with Dispersive Endotaxial Nanoprecipitations

“…Relaxor ferroelectrics (RFEs), by virtue of their unique characteristics, including a large dielectric permittivity in a wide temperature range, [ 12,13 ] a giant piezoresponse, [ 14–16 ] and large electrostrains, [ 2,17 ] have been the dominant candidates for the design of superior electrostrictive materials with large electrostrains. A series of strategies have been developed based on the modification of the polar nanoregions (PNRs) of RFEs by adjusting the proportion and changing the dynamic activity of the ergodic phase.…”

Understanding electrocaloric cooling of ferroelectrics guided by phase‐field modeling

“…(C1−C3) Microstructural evolution upon cooling the BC 0.22 TS x system: (C1) x = 0.02, (C2) x = 0.12, and (C3) x = 0.19. Cubic (C), tetragonal (T), orthorhombic (O), and rhombohedral (R) symmetries are classified by colors 66 …”

“…However, the two key factors usually do not go hand in hand, and usually, achieve a broad operating temperature region at the expense of sacrificing ΔT. Recently, Wang et al 66 reported the inducing novel state in (Ba 1−y Ca y )(Ti 1−x Sn x )O 3 system, the trirelaxor (TR) phenomenon at the crossover of the triple point and the relaxor 66 region and displayed that it can lead to giant dielectric response and enhanced electrocaloric property over a wide temperature range, as shown in Figure 3. The trirelaxor composition BC 0.22 TS 0.12 displays a relatively high peak within a comparatively wide temperature range simultaneously (ΔT = 0.5 K, T span = 21 K).…”