Zirconium Oxide and Other Oxides with the Fluorite Structure

Zirconium Oxide and Other Oxides with the Fluorite Structure 

Simple oxides with large cations - such as Zr, Th, and U - crystallize with the fluorite structure (the mineral fluorite itself is CaF2). Both, Zr02 and UO2 have been well studied and will be emphasized in this chapter, though neither story is simple. 

Although Y ions present only weak obstacles to dislocation motion [58], they are present in high concentrations and could, in theory, yield a large contribution to the flow stress. However, the crystals presently available apparently contain very small precipitates of ZrN [71] which provide stronger obstacles to slip than do unassociated Y ions [58, 72, 73]. Nonetheless, these unassociated Y ions do cause plastic instabilities, such as dynamic strain aging or the Portevin-Le Chatelier effect in 

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