Single Crystal Zirconia Shape Memory Ceramics

Zirconia based shape memory ceramics are a new class of shape memory material that offer many advantages over shape memory metals such as high operating temperatures, large transformation stresses, and chemical inertness.  However ceramics are inherently brittle which can lead to fracture after one or several transformation cycles. Recently, work has been done to overcome this limitation by applying microstructure engineering techniques that reduce or eliminate grain boundaries which are the cause of the fracture. In this experimental work tests were carried out on single crystal zirconia shape memory ceramics to explore the effect of sample size, dopant concentration, and crystal orientation.  The results show that single crystal shape memory ceramics can transform many times without fracturing. The resulting transformation strains are similar to those found in metals wheras the transformation stresses can be twice as large as shape memory metals due to the high strength of ceramics.