By means of x-ray diffraction, the authors have determined directly the coexistence region near the morphotropic phase change of the PLT, where the tetragonal and the rhombohedral phases coexist. In this region the lattice parameters of each phase do not change, and the relative amounts obey the leverage rule. The authors show that the morphotropic phase change may be considered as a first-order transition as a function of the temperature and the chemical potential (and not the concentration, as often supposed). They discuss the significance of their results concerning the explanation of the properties of this phase change.

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Composite materials based on Ti 2 NiCu alloy, exhibiting shape memory effect (SME), have the unique capability of temperature-controlled reversible actuation on micro-and nanoscale. Three approaches to realizing this objective are demonstrated. The first one involves creating an amorphouscrystalline composite by passing accurately controlled electrical pulses through a rapidly-quenched amorphous Ti 2 NiCu ribbon. After undergoing partial crystallization (40-60% of crystalline phase), the composite acquires SME, and can be trained to undergo reversible deformations by a single bend in the martensitic condition. The second approach involves a layered composite consisting of a layer of Ti 2 NiCu and an elastic metallic layer, such as Pt. It is found that the reversible deformation of the Ti 2 NiCu/Pt composite created by FIB milling is >1%, when the thickness of SME layer is reduced from 1 mm to 100 nm. Further reduction (below 100 nm) results in smaller deformation. The third approach combines these two methods. A layer of crystalline Ti 2 NiCu is covered by a layer of the same alloy in the amorphous state using FIB. The authors believe that these composites, exhibiting SME, will trigger the fabrication of many novel devices and open up new opportunities in diverse areas of nanoscience and nanotechnology.

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