Using the ferroelectric/ferroelastic effect at cryogenic temperatures for set-and-hold actuation

Abstract

The ferroelectric and ferroelastic properties of lead-zirconate-titanate (PZT) based stack actuators have been characterized at temperatures down to 25 K and under various levels of constant compressive stress. Experiments indicate that the coercive field and magnitude of strain at the coercive field display an inverse relationship with temperature. A factor of 5.5 increase in coercive field, and a factor of 4.3 increase in strain is observed at 25 K in comparison to the room-temperature conditions. This information was used to induce non-180° domain wall motion in the material through the application of electric fields at or near the coercive field. The change in remanent strain accompanying these effects was shown to increase in magnitude as temperature decreased, reaching values of 2000 ppm at 25 K. This behavior was also shown to be temporally stable even under compressive loads. Additionally, it was demonstrated that the material can be returned to its original strain state through a repolarizing electric field. This switchable behavior could be exploited for future set-and-hold type actuators operating at cryogenic temperatures.

Next-generation active telescope for space astronomy

“…Cryogenic testing of SiC substrates shows that cooling the mirror itself to 100 K or lower can be done without significantly degrading figure quality. 34 Cryocapable actuators have been characterized at temperatures as low as 25 K. 35,36 The PZT SFAs are installed so that they impart near-zero strain in their zero-volt state at room temperature. The actuator-substrate attachments are also designed to compensate the thermally induced differential strain when the mirror is cooled to its intended operating temperature.…”

“…Cryogenic testing of SiC substrates shows that cooling the mirror itself to 100 K or lower can be done without significantly degrading figure quality 34 . Cryocapable actuators have been characterized at temperatures as low as 25 K 35 , 36 …”

Dynamic Mechanical Analysis in the Investigation on Ferroelectrics

“…铁电体具有巨大的机电耦合能力, 更是革新了整个 传感器和超声领域。 Cross [11] 最早定义了弛豫铁电体 的三大特征, 最大介电值对应的温度具有频率色 散、铁电相变宽泛弥散以及相变后高温段仍具有较 大剩余极化。 对于铁电压电材料, 除了保证本身的电学特 性外, 还必须确保服役期间其力学性能有效。传 统的力学测试方法多在静态下进行, 然而在实际 应用中铁电压电材料常受到动态交变载荷的作用, 如铁电材料在太空望远镜中应用 [12] 、生态压电膜 在扬声器中的应用 [13] 以及铁电复合材料在减震阻 尼方面的应用等 [14][15][16] 。材料的动态力学行为, 指 材料在交变应力作用下的应变响应或交变应变作 用下的应力响应。因此, 相比常规的静态力学测 试, 测试动态力学行为更符合材料服役时的实际 情况。1909 年, Poynting [17] 最早利用振荡实验研究 材料的动态力学性能, 随后在测试仪器方面历经 了流变振动仪、扭摆、扭辫分析、振簧以及动态 热 机 械 分 析 仪 (DMA) 。 相 比 早 年 的 测 试 仪 器 , DMA 具有更宽的频域和温域测试范围, 并实现了 频率无级连续调节, 能测试的材料参数包括: 储 能模量、损耗模量、损耗因子、玻璃化转变温度、 固化剂体系的软化温度、特征频率和特征松弛时 间等 [18] 。 DMA 能模拟材料实际服役情况, 在不破坏样…”