The high-pressure phase sequence in nanocrystalline zirconia

X-ray diffraction and Raman data on the pressure induced phase transitions of a nanometric zirconia, ZrO<Subscript>2</Subscript>, are analyzed via a classical phenomenological Landau approach of the bulk. It is concluded that the initial tetragonal structure (D <Subscript>4h </Subscript> <Superscript>15</Superscript>), which is a metastable bulk state of zirconia at ambient conditions, evolves continuously towards the ideal cubic fluorite structure (O <Subscript> h </Subscript> <Superscript>5</Superscript>) via an intermediate tetragonal form (D <Subscript>4h </Subscript> <Superscript>14</Superscript>). The proposed phenomenological model describes consistently all experimental peculiarities, including the hybridization and softening of the low-frequency Raman active modes along with lattice-parameter anomalies. Copyright Springer-Verlag Berlin/Heidelberg 2003