Physical properties of piezoelectric oxides

压电氧化物的物理特性

• 批准号: 515433951
• 负责人: Privatdozent Dr. Eiken Haussühl
• 金额: --
• 依托单位: Professur für Kristallographie und Mineralogie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/515433951?language=en
• 关键词: Physical; properties; piezoelectric; oxides

In the field of functional materials, piezoelectric, ferroelectric and multiferroic systems have repeatedly been investigated in more or less detail in the past because of their potential applications, e.g., as sensors, electronic memories or ultrasonic transducers. This group of crystals includes oxide compounds that crystallize as piezoelectrics or ferroelectrics. Up to now, elastic properties of piezoelectric or ferroelectric oxides have been investigated in some cases as a function of temperature, but in most cases no further investigations have been carried out. This applies in particular to the temperature-dependent acoustic damping phenomena. The changes in mechanical properties can be measured particularly sensitively via the temperature dependence of the elasticity tensor, i.e., the thermoelastic coefficients, and thus with the aid of ultrasound techniques. The piezoelectric properties can also be derived using ultrasound techniques, in particular resonant ultrasound spectroscopy (RUS), as the electromechanical coupling is closely linked to their elastic properties.The aim of the project is to investigate the elastic and piezoelectric properties of selected oxidic crystals (sillenites, gehlenite, fresnoite, gamma-LiAlO2, LiGaO2) using the RUS technique as a function of temperature in order to analyze the basic features of the elastic and thermoelastic behaviour of these materials in a wide temperature range. Furthermore, the understanding of temperature-dependent acoustic damping phenomena and the correlation of crystal structure and thermoelastic properties will be deepened. Since the elastic properties reflect the three-dimensional bonding system of the crystal structure, ultrasound techniques such as RUS provide a highly sensitive probe for the detection of structural instabilities and phase transformations. The results will provide information on (1) the possible occurrence of temperature-dependent acoustic damping in the oxides (e.g. gehlenite, fresnoite) investigated here as was already observed for the sillenites, (2) whether a significant structural change occurs in the sillenites in the high-temperature range associated with the ultrasound damping, and (3) how the temperature-dependent elastic and piezoelectric tensor components of the sillenites change above the temperature limit of the ultrasound damping up to the melting point. Another aspect deals with the temperature-dependent correlation of increasing lithium diffusion of gamma-LiAlO2 and LiGaO2 (ambient temperature to melting point) and the elastic and piezoelectric properties, and a possible occurrence of ultrasound damping. In order to elucidate the possible reasons for a frequently occurring decrease of the piezoelectric effect, high-temperature conductivity and HT-DK measurements together with high-temperature structure determinations and temperature dependent powder-SHG measurements will be performed on a part of these compounds.

在功能材料领域，由于其作为传感器、电子存储器或超声换能器的潜在应用，压电体、铁电体和多铁体系统在过去或多或少都被反复详细地研究过。这组晶体包括以压电性或铁电性结晶的氧化物化合物。到目前为止，压电或铁电氧化物的弹性性质在某些情况下已经作为温度的函数进行了研究，但在大多数情况下还没有进一步的研究。这尤其适用于随温度变化的声学衰减现象。通过弹性张量的温度依赖性，即热弹性系数，可以特别灵敏地测量力学性能的变化，从而借助于超声波技术。由于机电耦合与材料的弹性性质密切相关，因此也可以使用超声技术，特别是共振超声光谱(RUS)来确定材料的压电性能。本项目的目的是利用共振超声技术研究选定的氧化物晶体(硅晶石、钙铝矿、钙钛矿、伽马-LiAlO2、LiGaO2)的弹性和压电性能，以分析这些材料在较宽温度范围内的弹性和热弹性行为的基本特征。此外，还将加深对随温度变化的声阻尼现象以及晶体结构和热弹性性质之间的关系的了解。由于弹性性质反映了晶体结构的三维键合系统，因此超声技术(如RUS)为检测结构不稳定性和相变提供了高灵敏度的探针。这些结果将提供如下信息：(1)在本文所研究的氧化物(如二辉橄榄石、闪锌矿)中可能会出现像已观察到的硅线石那样的随温度变化的声学衰减；(2)在与超声衰减有关的高温范围内，硅线石是否发生了显著的结构变化；(3)在超声衰减至熔点的温度极限以上，硅线石的弹性和压电张量分量随温度的变化情况。另一个方面涉及到γ-LiAlO2和LiGaO2(环境温度到熔点)的锂扩散增加与弹性和压电性能之间的温度相关性，以及可能发生的超声衰减。为了阐明压电效应频繁下降的可能原因，将对部分化合物进行高温电导率和HTDK测量，并进行高温结构测定和随温度变化的粉末倍频测量。