Cation self diffusion in nanocrystalline monoclinic zirconia

最近的研究表明，单斜氧化锆具有超塑性的行为。然而，为了进一步理解控制超塑性行为的精确机制，必须知道阳离子在这种特殊微观结构中的扩散系数。虽然有几个研究的阳离子扩散在其他多晶型的氧化锆，有没有单斜氧化锆的扩散的报告，因为它是不可能的，以制备致密的样品，通过烧结以上的单斜晶系到四斜晶系的转变温度（1443 K）。本计画的目标就是克服这些困难，并测量单斜氧化锆中的阳离子扩散。几乎完全致密的单斜氧化锆将通过在低于单斜相至四斜相转变温度下热等静压粉末来制备。在最近的一项研究表明，铪和镱可以分别作为锆和钇的示踪剂。示踪源将通过脉冲激光沉积沉积在单斜氧化锆上。扩散实验后，二次离子质谱法将被用来获得示踪剂的深度分布，从其中晶格和晶界阳离子扩散率将推导出。

It has been shown recently that monoclinic zirconia exhibits superplasticity-like behaviour. However, in order to further understand the precise mechanism that controls the superplastic behaviour, it is essential to know the diffusivities of the cations in this special microstructure. Although there are several studies on cation diffusion in other polymorphs of zirconia, there are no reports on the diffusion in monoclinic zirconia since it is not possible to prepare dense samples by sintering above the monoclinic to tetragonal transformation temperature (1443 K). The objective of this project is to overcome these difficulties and to measure cation diffusion in monoclinic zirconia. Nearly fully dense monoclinic zirconia will be prepared by hot isostatically pressing the powder below the monoclinic to tetragonal transition temperature. In a recent study it was demonstrated that hafnium and ytterbium can act as tracers for zirconium and yttrium, respectively. The tracer source will be deposited on monoclinic zirconia by pulsed laser deposition. After the diffusion experiment, secondary ion mass spectrometry will be used to obtain the tracer depth profiles wherefrom lattice and grain boundary cation diffusivities will be deduced.