| 1. |
- Sun, Haonan, et al.
(författare)
-
Large energy storage density in BiFeO3-BaTiO3-AgNbO3 lead-free relaxor ceramics
- 2020
-
Ingår i: Journal of the European Ceramic Society. - : Elsevier. - 0955-2219 .- 1873-619X. ; 40:8, s. 2929-2935
-
Tidskriftsartikel (refereegranskat)abstract
- Lead-free (0.70-x)BiFeO3-0.30BaTiO3-xAgNbO3+5‰mol CuO (abbreviated as BF-BT-xAN) ceramics were fabricated using a modified thermal quenching technique. BF-BT-xAN ceramics are of a perovskite structure with morphotropic phase boundary (MPB) and show strong relaxor properties. Remarkably, the high recoverable energy storage density of 2.11 J/cm3 is obtained for BF-BT-xAN with x = 0.14. For the x = 0.14 ceramics, its energy storage efficiency is as high as 84 % at relative low field of 195 kV/cm, together with an outstanding thermal stability in a broad temperature range from 25 °C to 150 °C. In addition, this ceramic maintains superior energy storage performance even after 8 × 104 electrical cycles due to its high densification after doping Ag2O and Nb2O5. The result suggests that lead-free BF-BT-xAN ceramics may be promising candidate for dielectric energy storage application.
|
|
| 2. |
- Wang, Xiangjian, et al.
(författare)
-
Enhanced piezoelectric, electrocaloric and energy storage properties at high temperature in lead-free Bi0.5(Na1-xKx)0.5TiO3ceramics
- 2019
-
Ingår i: Ceramics International. - : Elsevier. - 0272-8842 .- 1873-3956. ; 45:4, s. 4274-4282
-
Tidskriftsartikel (refereegranskat)abstract
- The piezoelectric, electrocaloric and energy storage properties were systemically investigated in lead-free Bi0.5(Na1-xKx)0.5TiO3 ceramics from room temperature to high temperature region. These ceramics can be poled completely to obtain large piezoelectric coefficient (104–153 pC/N) at low electric field of ~30 kV/cm. The piezoelectric propertyshows good thermal stability due to high depolarization temperature (Td). For BNKT20, a large low electric field-induced strain of 0.36% is obtained at 120 °C under 50 kV/cm, the corresponding normalized strain coefficient is up to 720 pm/V, which is larger than other BNT-based ceramics at high temperature region. The electrocaloric properties of these ceramics are studied via indirect and direct methods. Large EC value (~1.08 K) in BNKT20ceramic is obtained at 50 kV/cm using indirect calculation. Above 100 °C, the dielectricenergy storage density and efficiency of BNKT20 is still up to ~0.85 J/cm3 and 0.75, respectively. The BNKTx ceramics may become promising candidates in the fields of actuators, electrocaloric cooling and energy storage at high temperature region.
|
|
| 3. |
- Wang, Xiangjian, et al.
(författare)
-
Ferroelectric and antiferroelectric distortions coupling of nitride perovskite LaWN3 under epitaxial strain using first-principles calculations
- 2022
-
Ingår i: Europhysics letters. - : Institute of Physics (IOP). - 0295-5075 .- 1286-4854. ; 140:5
-
Tidskriftsartikel (refereegranskat)abstract
- LaWN3, a novel nitride perovskite, have been synthesized and its piezoelectric properties have been investigated (TALLEY K. R. et at., Science, 374 (2021) 1488). However, the understanding of its ferroelectric properties under the external strain is still lacking. Here, the misfit-strain-dependent coupling between anti-ferrodistortions (AFD) and ferroelectric (FE) distortions has been studied by using a first-principle approach. It can be observed that AFD and FE distortions can work cooperatively with each other as the compressive strain increases, and the coupling energy between them is found to work in different ways under various strains. Our results show that the coupling tends to stabilize the ground structure when the compressive strain is smaller than -1.9%, it works oppositely when the compressive strain becomes larger than 1.9%. Our results can provide us with more hints about the influence of the epitaxial strains on the intrinsic coupling behavior in the perovskite ferroelectric compounds, which is very important for us to design and fabricate new kinds of functional materials.
|
|
| 4. |
- Wang, Xiangjian, et al.
(författare)
-
Large electrical strain in lead-free K0.5Na0.5NbO3-based ceramics by heterovalent doping
- 2023
-
Ingår i: Journal of Materiomics. - : Elsevier. - 2352-8478 .- 2352-8486. ; 9:5, s. 959-970
-
Tidskriftsartikel (refereegranskat)abstract
- Heterovalent doped (K0.48-0.07xNa0.52-0.43xBi0.5x)(Nb0.95-0.95xSb0.05-0.05xZrx)O3 ceramics were fabricated using conventional solid-state reaction. Then, the phase structures, dielectric, ferroelectric, and electric-strain properties were investigated. The compositions were tuned to be located at polymorphic phase boundary with increasing heterovalent Bi3+ and Zr4+ doping levels. A large strain of 0.19% was obtained at relatively low electric fields of 30 kV/cm in the composition of x = 0.04. The normalized large-signal d33* values were approximately 633 pm/V under a low driving electric field of 30 kV/cm, which were comparable or larger than the values reported for other lead-free families. The large strains obtained can be attributed to the formation of nanodomains and high-density domain walls, which were confirmed by the observations of domain morphology using transmission electron microscopy (TEM) technique. Excellent temperature stability of the strain properties of the x = 0.04 sample could be ascribed to the sluggish behaviour for the local structural heterogeneity in heterovalent-ion doped KNN ceramic. Theoretical simulations revealed that the Zr4+ produce the local stress at the BO6 octahedra and Bi3+ could yield off-centering of AO12 ployhedron due to the nature of Bi 6s lone pair electrons, which induced lattice expansion and local distortions in the sample. The local displacements are strongly anisotropic in heterovalent-ion doped system. It is believed that random local fields exist in these compositions owing to the eixstence of charge distribution. Such heterovalent doping of Bi3+ and Zr4+ could destory simutiously the orthorhombic symmetry and the short-range ferroelecctric order, leading to the formation of complex nanodomains and local structral hetergenenity. Heterovalent doping may, therefore, offer a new avenve to design novel K0.5Na0.5NbO3 (KNN) -based materials for their mutifunctional applications.
|
|
| 5. |
- Wang, Xiangjian, et al.
(författare)
-
Multifunctionality in (K,Na)NbO3-based ceramic near polymorphic phase boundary
- 2021
-
Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 130:6
-
Tidskriftsartikel (refereegranskat)abstract
- The 0.95K0.42Na0.58Nb0.96Sb0.04O3–0.02BaZrO3–0.03Bi0.5K0.5HfO3 ceramic was fabricated via a conventional solid-state reaction. This ceramic exhibits the diffuse polymorphic phase boundary (PPB) near room temperature. The dielectric, ferroelectric, electromechanical, electrocaloric, and dielectric energy storage properties were studied systemically. The normalized large signal d33* values are approximately 400–600 pm/V at measured temperatures and electric fields, which are larger than or comparable with the values reported in other lead-free compositions. The electrocaloric strength is enhanced at the broad region of PPB provided by the indirect and direct measurements. At low field of 30 kV/cm, the dielectric energy storage is ∼0.12–018 J/cm3 at relative broad temperature range due to the diffuse nature of polymorphic phase boundary. Theoretical simulations reveal that multi-element dopants, such as Sb5+, Hf4+, Zr4+, and Bi3+ ions, could induce the breaking of local structure symmetry in the orthorhombic phase to form the PPB. In addition, the charge distribution may also break the long-range ferroelectric order through the analysis of Bader charge. Our study suggests that the K0.5Na0.5NbO3-based ceramic exhibits improved performance and good thermal stability in piezoelectric, electrocaloric, and dielectric energy storage characteristics in terms of the design of multi-element dopants to form the PPB and it will benefit the promising applications in electronic devices.
|
|
