Pressure-induced structural phase transitions in zirconia under high pressure

Abstract

Angular-dispersive x-ray in situ powder-diffraction experiments have been performed on pure zirconia, Zr02, at room temperature under high pressure up to 50 GPa. Under increasing pressure four phases were successively encountered: baddeleyite (monoclinic, P21/c) from normal pressure up to about 10 GPa, orthorhombic-1 (Pbca) to 25 GPa, orthorhombic-11 to 42 GPa, and orthorhombic-111 above 42 GPa. The unit-cell parameters and the volume have been determined as a function ofpressure. The bulk moduli of the two lower pressure phases have been calculated using Birch's equation of state. The bulk modulus of baddeleyite, 95 GPa, is much lower than expected from bu1k modulus-volume systematics, 195 GPa, while for the orthorhombic-1 phase, the experimental and calculated values are almost identical. A generalized P-T diagram for Zr02, including an orthorhombic-IV phase, is proposed and discussed. The phase transition to orthorhombic-11 and orthorhombic-111 phases can be described by a simple rotation of the unit cell of the orthorhombic-1 phase about either the b axis to form the orthorhombic-11 phase or a axis to form the orthorhombic-111 phase. All high-pressure cells (orthorhombic-1, -11, and -111) have eight formula units (Z =8). The orthorhombic-11 phase was found not to have the cotunnite PbC12-type structure which was proposed previously. There is no longer any examp1e of a compound which transforms to such a cotunnite-type structure under high pressure. The behavior of zirconia and hafnia under high pressure is different although they have very close chemical properties at ambient pressure and identical structures in the two lower-pressure phases.

New high-pressure phase and equation of state of Ce2Zr2O8

“…37 The monoclinic baddeleyite-type ZrO 2 transforms to orthorhombic cotunnitetype ZrO 2 at high pressure. 36 Leger et al have reported the sequence of structural transitions as baddeleyite-orthorhombic-I (Pbca)-orthorhombic-II-orthorhombic-III, occurring at room temperature at around 10, 25, and 42 GPa, respectively. 35 Thus, it is not uncommon to expect a pressure-induced structural distortion in Ce 2 (Fig.…”

“…34,35 HP studies of ZrO 2 and HfO 2 indicate the formation of orthorhombic or monoclinic phases. [35][36][37] HP studies of columbite-type ZrTiO 4 (HfTiO 4 ) show the formation of baddeleyite-related HP phases above 9 (2.7) GPa. 38 The diverse possible structural transitions of fluorite, zirconia, and pyrochlore create more interest in the HP behavior of Ce 2 , using glycine as a fuel.…”

Fast and Tunable Synthesis of ZrO2 Nanocrystals: Mechanistic Insights into Precursor Dependence

“…However, the chloride precursor leads to Table 2). According to literature 40,41 , the obtained crystallographic ZrO2 phase can depend on the applied pressure, however little is known on the influence of the pressure that arises during a solvothermal treatment on the ZrO2 phase formation. An anhydrous alcohol was added to the propoxide precursor to raise to pressure of the system during microwave synthesis.…”

Observation of the negative pressure derivative of the bulk modulus in monoclinic ZrO2

“…So far, there have been many reports on high-pressure behavior of the pure ZrO 2 . [7][8][9][10][11][12][13][14][15] According to previous experimental studies, the M phase, with increasing pressure, transforms to the orthorhombic I (O-I phase, space group: Pbca) 9 around 4 GPa, 10 and then, to orthorhombic II (O-II phase, space group: Pnma) 7,13 phase around 21 GPa at room temperature. 15 The structure of the O-I phase, which corresponds to a distorted fluorite structure, 9 is similar to that of the M phase and both phases have sevenfold polyhedral coordination.…”