Fracture of Ferroelectric / Ferroelastic Ceramics

许多技术上重要的陶瓷是铁弹性的。这包括锆钛酸铅（PZT），其是广泛用于压电应用的铁电体，以及镧锶钡（LSM），其是用作固体氧化物燃料电池中的阴极材料的电子导体。建议的研究的目的是调查和理解的铁弹性陶瓷受到压缩载荷的缺口断裂被忽视的问题。陶瓷通常在压缩中预加载以避免脆性破坏。然而，我们的初步工作已经表明，压-压加载的铁电陶瓷可以产生断裂在令人惊讶的小远场应力。研究结果对铁弹陶瓷元件的设计和性能具有重要意义。这种效应的起因可能是铁弹性陶瓷中产生的相对较大的应变不可逆性和卸载时可能产生的拉应力。在极性材料的情况下，缺口处的电位移可能会引起大的局部电场，这可能会产生额外的损坏。研究的目的是调查影响断裂的因素，确定断裂和裂纹扩展的机制，并使用有限元分析对问题进行建模。这项工作的一个重要成果将是提高对铁电/铁弹陶瓷元件良好设计实践的了解。

Many technologically important ceramics are ferroelastic. This includes lead zirconate titanate (PZT), which is a ferroelectric that is widely used for piezoelectric applications, and lanthanum strontium manganate (LSM), which is an electronic conductor that is used as a cathode material in solid oxide fuel cells. The objective of the proposed research is to investigate and understand the overlooked problem of fracture at notches in ferroelastic ceramics subjected to compressive loading. Ceramics are often preloaded in compression to avoid brittle failure. However, preliminary work by us has demonstrated that compression-compression loading of ferroelectric ceramics can produce fracture at surprisingly small far-field stresses. The results of this work have significant implications for the design and performance of ferroelastic ceramic components. The origin of the effect may be the relatively large strain irreversibility produced in ferroelastic ceramics and the tensile stresses that this can generate on unloading. In the case of polar materials, electric displacements at the notch may induce large local electric fields that may produce additional damage. The objective of the research is to investigate the factors that influence fracture, determine the mechanisms for fracture and crack growth and to model the problem using finite element analysis. An important outcome of the work will be an improved knowledge of good design practice for ferroelectric / ferroelastic ceramic components.