Sandwichlike strain glass phase diagram of Ti49Ni51-xPdx

Two kinds of phase diagrams can be observed in doped ferroic materials. A glass phase diagram is formed by doping a nontransforming end into a ferroic matrix, while doping a transforming end forms phase diagrams with a phase boundary separating two different ferroic phases. Here we report a phase diagram in which a strain glass state is sandwiched between two distinct ferroelastic phases. This type of phase diagram in doped ferroelastic materials bridges the one with a glass state and the one with a phase boundary. We thus establish a 3D phase diagram of Ti50-yNi50+y-xPdx ternary alloys, in which the evolution of these different kinds of phase diagrams can be observed. An understanding from the Landau free energy landscape suggests that the transforming doping end plays three roles in influencing the ferroic matrix: (1) to destabilize the ferroic matrix phase, (2) to stabilize another ferroic phase different from the matrix one, and (3) to create random local fields. The competition between these effects determines various phase diagrams in doped ferroic materials. Thus our work may provide an experimental foundation for a unified mechanism to all three kinds of phase diagrams.