Verification of Existence of Cubic Zirconia at High Temperature

Abstract

905-906 (1961 ). 3 S. Hurwitt arid A. Appel, "Study of Phase Transformation With a Low Thermal Inertia High Temperature Diffractometer Attachnierit," Norrl,.o Kept., 8 [5] 90-91 (1961).

From superhard to hard: A review of transition metal dioxides TiO2, ZrO2, and HfO2 hardness

“…Additionally, for the case of TiO 2 , there are three phases found at ambient conditions: brookite (rare polymorph [26]) and anatase are stable phases, whereas rutile (RT) is a metastable phase formed at high temperatures. Additionally, there are other observed phases at high temperature for ZrO 2 and HfO 2 : tetragonal [84,85] and cubic [86,87] phases. It is also important to note that as the pressure increases, there is no trend of increasing or decreasing in structural symmetry.…”

High-temperature calorimetry of zirconia: Heat capacity and thermodynamics of the monoclinic–tetragonal phase transition

“…It is well known that, at atmospheric pressure, ZrO 2 shows three polymorphs below the melting temperature of (2983 ± 15) K [1]. On heating, ZrO 2 undergoes successive phase transitions from a monoclinic phase (m-phase; P2 1 /c) [2] to a tetragonal phase (t-phase; P4 2 /nmc) [3] near T = 1450 K and from the tphase to a cubic phase ðFm 3mÞ [4] at about T = 2640 K. On cooling, however, the transition from the t-phase to the m-phase occurs near T = 1250 K, representing a remarkable thermal hysteresis of over 200 K [5]. In addition, the transition is accompanied by a large volume change of $3% (contraction on heating and expansion on cooling) [6] in line with the change in coordination number of Zr cations from seven in the m-phase to eight in the t-phase.…”

Heat capacity and thermodynamic functions of zirconia and yttria-stabilized zirconia

“…Pure zirconia ZrO 2 has three polymorphs below the critical point T = (2983 ± 15) K. (1) The highest temperature solid phase has fluorite-type of face-centered cubic structure, (2) which is stable between the critical point and the cubic-to-tetragonal phase transition at T = 2640 K. On cooling, zirconia undergoes a structural phase transition from tetragonal (3) to monoclinic (4) at T = 1440 K, which is associated with a large volume change (≈3 per cent) (5) so great that the crystal cracks. However, the cubic phase can be stabilized at room temperature by adding di-or trivalent oxides such as CaO, Y 2 O 3 , Sc 2 O 3 , and so forth.…”