Shepley Philippa M, Stoica Laura A, Li Yang, Burnell Gavin, Bell Andrew J
School of Chemical and Process Engineering, University of Leeds, Leeds, UK.
School of Physics and Astronomy, University of Leeds, Leeds, UK.
Sci Rep. 2019 Feb 21;9(1):2442. doi: 10.1038/s41598-019-38995-9.
The mechanisms underlying the anomalously large, room temperature piezoelectric activity of relaxor-PbTiO type single crystals have previously been linked to low temperature relaxations in the piezoelectric and dielectric properties. We investigate the properties of Pb(InNb)O-Pb(MgNb)O-PbTiO between 10 and 300 K using dielectric permittivity measurements. We compare results on single crystal plates measured in the [001] and [111] directions with a polycrystalline ceramic of the same composition. Poled crystals have very different behaviour to unpoled crystals, whereas the dielectric spectrum of the polycrystalline ceramic changes very little on poling. A large, frequency dependent dielectric relaxation is seen in the poled [001] crystal around 100 K. The relaxation is much less prominent in the [111] cut crystal, and is not present in the polycrystalline ceramic. The unique presence of the large relaxation in poled, [001] oriented crystals indicates that the phenomenon is not due their relaxor nature alone. We propose that heterophase dynamics such as the motion of phase domain boundaries are responsible for both the anomalous electromechanical and dielectric behaviour.
弛豫型-PbTiO 型单晶在室温下具有异常大的压电活性，其潜在机制此前一直与压电和介电性能的低温弛豫有关。我们使用介电常数测量方法研究了 Pb(InNb)O-Pb(MgNb)O-PbTiO 在 10 至 300 K 之间的性能。我们将在[001]和[111]方向测量的单晶片结果与相同成分的多晶陶瓷进行了比较。极化晶体与未极化晶体的行为有很大不同，而多晶陶瓷的介电谱在极化后变化很小。在极化的[001]晶体中，在 100 K 左右观察到一个大的、频率依赖的介电弛豫。在[111]切割晶体中，这种弛豫不太明显，并且在多晶陶瓷中不存在。极化的[001]取向晶体中独特存在的大弛豫表明，该现象不仅仅是由于它们的弛豫特性。我们提出，诸如相畴边界运动等异相动力学是异常机电和介电行为的原因。
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