Figure 1: Crystal structures of HfO2 polymorphs.
From: Real-time atomistic observation of structural phase transformations in individual hafnia nanorods
The unit cell of three phases of HfO2, showing the small atomic displacements, and preservation of the coordination environments, during transformation between the phases. The monoclinic to tetragonal (a,b) and tetragonal to cubic (b,c) transitions occur at ∼1700 and ∼2600 °C, respectively, at atmospheric pressure. Arrows in (a) show displacements necessary to transform to the tetragonal phase (b). Hafnium atoms are shown as olive spheres, whereas oxygen atoms are shown as red spheres.
