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首页> 外文学位 >Thermally and electrically induced antiferroelectric ↔ ferroelectric transition in perovskite ceramics for use in high energy density capacitors.
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Thermally and electrically induced antiferroelectric ↔ ferroelectric transition in perovskite ceramics for use in high energy density capacitors.

机译：在高能量密度电容器中使用的钙钛矿陶瓷中的热和电感应反铁电↔铁电跃迁。

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摘要

Dielectric capacitors traditionally have very high power and short response time but low energy storage capability compared to batteries and electrochemical capacitors. For efficient and reliable energy storage of intermittent sources such as wind and solar, energy storage devices would ideally have both high power and energy densities. The studies of high energy density capacitor dielectrics presented in this thesis are part of the effort to move toward this paradigm.;Ceramic antiferroelectric compositions such as Pb0.99 Nb0.02[(Z0.57Sn0.43)1-yTi y]0.98O3 (PNZST 43/100y/2) show promise as dielectrics in high energy density capacitors due to a sharp and highly tunable phase transition from antiferroelectric (AFE) to ferroelectric (FE). This transition results in a significant increase in polarization at a critical electric field, storing a large amount of electrical energy that can be released during unloading if the material undergoes the reverse transition at a relatively high electric field.;These compositions also display thermally induced phase transitions, which must be understood in order to more fully understand how antiferroelectric properties develop. Several thermal characterization methods (dielectric constant and loss tangent, storage modulus and mechanical loss tangent, thermal expansion, and calorimetry) have been utilized to uncover the nature of complex phase transitions in lead-free pseudo-antiferroelectric composition (Bi1/2 Na1/2)0.93Ba0.07TiO3 (BNT-7BT) and the lead-containing PNZST 43/8/2 composition. These experiments reveal the first order nature of the ferroelectric to antiferroelectric and the antiferroelectric to multi-cell cubic transitions, and the second order nature for the multi-cell cubic to single-cell cubic transition in PNZST43/8/2. In the BNT-7BT, the dielectric anomalies are not accompanied by any structural transitions in the unpoled state. However, after electrical poling to a ferroelectric phase with large domains, the thermal depolarization process corresponds to a first order structural transition.;In general, the antiferroelectric to ferroelectric transition is accompanied with a volume expansion. Therefore, the critical field may be altered in specimens with varying electrode size, where the outer unpoled material exerts radial pressure on the expanding electroded material. The impact of electrode coverage on antiferroelectric PNZST43/100y/2 capacitors has been investigated at a series of temperatures in a series of compositions. Self-exerted mechanical confinement was found to shift the critical electric fields of the transitions to higher values and moderately increased the energy storage density. Phase field modeling reveals that, in addition to the self-confinement, material defects also contribute to these enhancements.
机译：传统上，与电池和电化学电容器相比，介电电容器具有很高的功率和较短的响应时间，但能量存储能力却很低。为了有效地和可靠地存储间歇性能源（例如风能和太阳能）的能量，储能设备最好同时具有高功率和能量密度。本文提出的对高能量密度电容器电介质的研究是朝着这一范例努力的一部分。陶瓷反铁电成分，如Pb0.99 Nb0.02 [（Z0.57Sn0.43）1-yTi y] 0.98O3 （PNZST 43 / 100y / 2）由于从反铁电（AFE）到铁电（FE）的急剧且高度可调的相变，显示出有望在高能量密度电容器中用作电介质。这种转变导致临界电场下极化的显着增加，如果材料在相对高的电场下经历了反向转变，则可以在卸载过程中存储大量电能，这些能量可以在卸载过程中释放出来;这些成分还显示出热诱导相为了更充分地理解反铁电特性的发展，必须理解这种转变。几种热表征方法（介电常数和损耗角正切，储能模量和机械损耗角正切，热膨胀和量热法）已被用来揭示无铅拟反正电子组分（Bi1 / 2 Na1 / 2）中复杂相变的性质。 0.93Ba0.07TiO3（BNT-7BT）和含铅的PNZST 43/8/2组成。这些实验揭示了PNZST43 / 8/2中铁电到反铁电和反铁电到多单元立方转变的一阶性质，以及多单元立方到单细胞立方转变的二阶性质。在BNT-7BT中，介电异常在非极化状态下不伴有任何结构转变。然而，在电极化到具有大畴的铁电相之后，热去极化过程对应于一阶结构转变。通常，反铁电到铁电转变伴随着体积膨胀。因此，在具有变化的电极尺寸的样品中，临界场可能会发生变化，其中外部未极化材料会在膨胀的带电极材料上施加径向压力。在一系列温度下以一系列成分研究了电极覆盖率对反铁电PNZST43 / 100y / 2电容器的影响。发现自我施加的机械限制将转变的临界电场转移到更高的值，并适度增加了能量存储密度。相场建模表明，除了自我约束之外，材料缺陷也有助于这些增强。

著录项

  • 作者

    Young, Samuel Eli.;

  • 作者单位

    Iowa State University.;

  • 授予单位 Iowa State University.;
  • 学科 Engineering Materials Science.
  • 学位 M.S.
  • 年度 2013
  • 页码 80 p.
  • 总页数 80
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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