• Domain wall free polar structure enhanced photodegradation activity in nanoscale ferroelectric BaxSr1-xTiO3

      Wang, Yaqiong; Zhang, Man; Jianguo, Liu; Zhang, Haibin; Li, Feng; Tseng, Chiao-Wei; Yang, Bin; Smith, Graham C.; Zhai, Jiwei; Zhang, Zhen; et al.
      Ferroelectric materials exhibit anomalous behavior due to the presence of domains and domain walls which are related to the spontaneous polarization inherent in the crystal structure. Control of ferroelectric domains and domain walls has been used to enhance device performances in ultrasound, pyroelectric detectors and photovoltaic systems with renewed interest in nanostructuring for energy applications. It is also known that the ferroelectric including domain walls can double photocatalytic rate and increase carrier lifetime from μs to ms[1] However, there remains a lack of understanding on the different contributions of the domain and domain walls to photo-catalytic activities. Herein it is found, by comparing samples of nanostructured BaxSr1 xTiO3 with and without a polar domain, that the material with polar domains has a faster reaction rate (k=0.18 min-1) than the non polar one (k = 0.11 min-1). It is further revealed that the observed enhanced photoactivity of perovskite ferroelectric materials stems from the inherent polarization of the domain instead of domain walls. Here, the new understanding of the underlying physics of materials with a spontaneous dipole opens a door to enhance the performance of light induced energy harvesting systems.
    • Perovskite Srx(Bi1-xNa0.97-xLi0.03)0.5TiO3 ceramics with polar nano regions for high power energy storage

      Wu, Jiyue; Mahajan, Amit; Riekehr, Lars; Zhang, Hangfeng; Yang, Bin; Meng, Nan; Zhang, Zhen; Yan, Haixue; Queen Mary University of London; Uppsala University; University of Chester (Elsevier, 2018-06-06)
      Dielectric capacitors are very attractive for high power energy storage. However, the low energy density of these capacitors, which is mainly limited by the dielectric materials, is still the bottleneck for their applications. In this work, lead-free single-phase perovskite Srx(Bi1-xNa0.97-xLi0.03)0.5TiO3 (x=0.30 and 0.38) bulk ceramics, prepared using solid-state reaction method, were carefully studied for the dielectric capacitor application. Polar nano regions (PNRs) were created in this material using co-substitution at A-site to enable relaxor behaviour with low remnant polarization (Pr) and high maximum polarization (Pmax). Moreover, Pmax was further increased due to reversible electric field induced phase transitions. Comprehensive structural and electrical studies were performed to confirm the PNRs and the reversible phase transitions. And finally a high energy density (1.70 J/cm3) with an excellent efficiency (87.2%) was achieved using the contribution of PNRs and field-induced transitions in this material, making it among the best performing lead-free dielectric ceramic bulk material for high energy storage.