Ferroelectric-Relaxor Crossover and Energy Storage Properties in Sr₂NaNb₅O₁₅-Based Tungsten Bronze Ceramics

Abstract

Filled and unfilled Sr 2 NaNb 5 O 15 -based tungsten bronze ceramics based on Gd doping were prepared using a traditional solid-state reaction method. Relaxor behaviors of the two different systems were analyzed, and the corresponding energy storage performance was also characterized. With the support of weakly coupled polar nanoregions and a non-polar matrix, an energy storage density of 2.37 J/cm 3 and an efficiency of 94.4% were obtained in the Sr 1.82 Gd 0.12 NaNb 5 O 15 ceramic. A discharge energy density of 2.51 J/cm 3 and a power density of 59.1 MW/cm 3 further proved its prospect for practical applications. In addition, the thermal stability and fatigue resistance of the ceramic were also evaluated. At the same time, under the theoretical framework of a perovskite and tungsten bronze, the contribution of vacancies to the local structure and relaxor behavior was briefly discussed. Because the currently used ceramics do not contain easily reducible metal oxides, this work lays the foundation for the development of multilayer ceramic capacitors that use base metals as internal electrodes.

Dielectric property and energy storage performance enhancement for iron niobium based tungsten bronze ceramic

“…The red shift of the internal mode is believed to be related to the expansion of the octahedra and the weakening of the B–O bond strength, which usually shows relaxation behavior and lower polarization intensity. 44 The red shift of Raman mode for SSNFN here is consistent with its stronger relaxor nature which has been revealed by the above experimental result. Third, Raman mode intensity of SSNFN is much smaller than SNN, although the data are collected at the same condition.…”

Superior Energy Density Achieved in Unfilled Tungsten Bronze Ferroelectrics via Multiscale Regulation Strategy

“…As a result, W rec increases to 5.895 J cm −3 with an enhancement of 50.69%, and 𝜂 is also improved to 85.37%. The achievement of optimized composition of Sr 0.425 La 0.1 □ 0.05 Ba 0.425 Nb 1.4 Ta 0.6 O 6 can also be supported by a systematical investigation on the [17,18,[22][23][24][27][28][29][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] structure and properties of Sr 0.425 La 0.1 □ 0.05 Ba 0.425 Nb 2−x Ta x O 6 ceramics with different Ta 5+ concentrations, which is summarized in Figures S1-S4 (Supporting Information). A comparison of the ESP of our SLBNT ceramics and previously reported lead-free bulk ceramics are illustrated in Figure 2e.…”

“…e) The comparison of W rec and η values of SLBNT and other recently reported lead‐free bulk ceramics. [ 17,18,22–24,27–29,38–53 ]…”

“…[ 21,37,63 ] Besides, extra structural vacancies at the A‐site further weaken the coupling of PNRs, thereby influencing the relaxor behavior. [ 51 ] Additionally, the enhanced relaxor behavior is also quantitatively estimated by the calculated diffuseness degree ( γ ) in Figure S7 (Supporting Information) via the Curie–Weiss law ($$\frac{1}{{{\varepsilon }_{\rm{r}}}} - \frac{1}{{{\varepsilon }_{\rm{m}}}} = \frac{{{{( {T - {T}_{\rm{m}}} )}}^\gamma }}{C}$$, where ε m is the maximum permittivity and C is a constant). [ 64 ] The value of γ rises dramatically and monotonously from SBN (1.19) to SLBN (1.79) and SLBNT (1.94).…”

“…It is evident that the excellent overall performance of SLBNT ceramics leads the field in tetragonal tungsten bronze structure ferroelectric ceramics and can even be comparable with some state-of-the-art perovskite structure ceramics. [17,18,[22][23][24][27][28][29][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] Figure 3a shows the X-ray diffractometer (XRD) patterns of SBN, SLBN, and SLBNT ceramics. All the patterns reveal pure tungsten bronze structure, indicating that the La 3+ and Ta 5+ successfully entered the SBN host lattice.…”