Browsing by Author "Zhang, W"

Filter results by typing the first few letters
Now showing 1 - 4 of 4
  • Thumbnail Image
    item: Article-Full-text
    Effect of post-annealing on microstructure and piezoelectric properties of ZnO thin film for triangular shaped vibration energy harvester
    (Elsevier, 2019) Zhang, X; Wang, P; Liu, X; Zhang, W; Zhong, Y; Zhao, H; Shi, S; Jin, S; Amarasinghe, YWR
    In this paper, a triangular shaped piezoelectric vibration energy harvester (TS-PVEH) with zinc oxide (ZnO) thin films as the piezoelectric layer is reported. The effect of post-annealing temperature on the microstructure and piezoelectric performance of ZnO thin film deposited by magnetron sputtering method is investigated firstly. The results show that the optimum post-annealing temperature of 150 °C was the most beneficial to improve the piezoelectric properties of ZnO thin films. Four prototypes of TS-PVEH with different structure parameters are fabricated and optimized. The simulation and experiment results indicate that the height and width of the triangular structure have a significant influence on the vibration mode and the output performance of TS-PVEHs. The optimization results indicate that the third prototype has the best output performance. Its open-circuit voltage and short-circuit current are 290 mV and 1.25 μA, respectively, when the vibration acceleration is 5 m/s2 and the frequency is 56 Hz. Moreover, it has the highest load power density of 0.035 μW/cm2 when the load is 0.1MΩ.
  • Thumbnail Image
    item: Article-Full-text
    Solvothermal reaction and piezoelectric response of oriented KNbO3Polycrystals
    (ACS Publications, 2021) Yang, D; Wang, Y; Li, L; Yao, M; Zhang, W; Gu, H; Zhang, S; Fan, M; Sewvandi, GA; Hu, D
    KNbO3 (KN) piezoelectric polycrystals were prepared by a two-step solvothermal reaction process with the managed organic solvents as reaction mediums at a low temperature for a short time. In the solvothermal reaction system, the formation mechanism of polycrystalline KN is mainly the dissolution–deposition mechanism. The influences of alkalinity, viscosity, and the polarity for reaction mediums on the formation of the niobates were investigated. The chemical reaction mechanisms of niobate products and formation mechanism of niobate crystals from the precursor were clarified. The regulating and controlling mechanism of the phase compositions, the morphologies, and the lattice constants for the niobates obtained in varied reaction mediums were revealed. The obtained KN piezoelectric polycrystals are constructed from oriented KN nanocrystals. Piezoelectric hysteresis loops of cuboid KN polycrystals were detected for the first time. A prepared cuboid KN polycrystal shows an average d33* value of 32 pm/V. The study provides a strategy for the development of oriented KN piezoelectric materials to apply the orientation engineering.
  • Thumbnail Image
    item: Article-Abstract
    Topochemical conversion of the discontinuous-zone-axis to form bismuth titanate oriented polycrystal nanocomposites
    (Royal Society of Chemistry, 2021) Wang, Y; Yang, D; Yao, M; Li, L; Huang, Z; Zhang, W; Han, Y
    Bismuth titanate based materials have wide potential applications in the fields of dielectrics, piezoelectrics, ferroelectrics, catalysis and energy storage. In this study, a two dimensional (2-D) layered H1.07Ti1.73O4·nH2O (HTO) crystal was used as a precursor to prepare 2-D bismuth titanate oriented polycrystal nanocomposites using two kinds of Bi3+ sources. The chemical reaction mechanisms for the formation of bismuth titanates are proposed, and the crystal structures and their conversions are also identified. The formation mechanism of the discontinuous-zone-axis is revealed. The obtained bismuth titanates are oriented polycrystals constructed from the orientation nanocrystals. In the process of forming the oriented polycrystal, the zone axis of the bismuth titanates obtained under different reaction conditions can vary even if the same reactants are used in the reaction. The certain topological correspondences among the oriented polycrystal, the precursor, and the intermediate, as well as the formation of bismuth titanates with a discontinuous-zone-axis based on a topochemical mesocrystal conversion reaction, were proposed. The special arrangement structure of the TiO6 octahedral layers accommodating in the HTO crystal is the main reason for the constant change of the zone axis of the bismuth titanate nanocomposite. However, based on the crystallographic investigation of the reaction mechanism involved in the formation process of construction of the bismuth titanate oriented polycrystal nanocomposite from the HTO crystal, it is found that the topochemical mesocrystal conversion reaction with a discontinuous-zone-axis is different from the conventional topochemical reactions. This may be attributed to the combination of the HTO matrix and Bi3+. It is vital to study the controllable preparation of bismuth titanate based nanocomposites and further understand the topochemical reaction.
  • Thumbnail Image
    item: Article-Full-text
    Topological relations and piezoelectric responses of crystal-axis-oriented BaTiO3/CaTiO3 nanocomposites
    (Royal Society of Chemistry, 2017) Hu, D; Niu, X; Ma, H; Zhang, W; Sewvandi, GA; Yang, D; Wang, X; Wang, H; Kong, X; Feng, Q
    2D crystal-axis-oriented mesocrystalline BaTiO3/CaTiO3 (BT/CT) nanocomposites with high-density heteroepitaxial interfaces were synthesized by a two-step solvothermal soft chemical process. The nanostructures, formation mechanism, topological relations between the BT and CT, and piezoelectric responses of the nanocomposites were investigated. The mesocrystalline nanocomposites are polycrystals constructed from crystal-axis-oriented BT and CT nanocrystals with the same crystal-axis orientation, respectively. The directions of the [001] and [1−10] of crystalline BT correspond to the directions of the [0−10] and [100] of crystalline CT, respectively. The mesocrystalline nanocomposites were formed via an in situ topochemical mesocrystal conversion mechanism. The density of the artificial BT/CT heteroepitaxial interface in these mesocrystalline nanocomposites can be adjusted by regulating the fraction of BT and CT in the nanocomposites. The mesocrystalline BT/CT nanocomposite with the composition close to BT/CT = 1/1 presents a large piezoelectric response owing to the lattice strain derived from its heteroepitaxial interfaces with the high density in the nanocomposite.