Cubic Zirconia

Cubic zirconia (Fm3m) has a fluorite structure with one formula unit (Z = 1) in the primitive cell. This cell contains one zirconium ion located at (0, 0, 0) and coordinated with eight equidistant oxygen ions. The two oxygen ions are located at (3, 3, 3) and (3A 3A 3), both tetrahedrally coordinated to four zirconium ions. The nonprimitive face-centered arrangement is illustrated in Fig. 2 and contains four zirconium ions located at (0, 0, 0), (A A 0), (A 0, */2), and (0, A */2). The eight oxygen ions are located at (‘A 3, A, (3,3, 3), (A 3, 3), (3, 3, 3), (3, 3, 3), (3, 3, 3), (3, 3, 3), and (3, 3, 3). The translational vectors for this structure are

h = ( ,2)

*2 = (, 0,“), (1) ts = , 2,0)-

General crystallographic correlations for this structure are given in Table 1. Experimental measurements of the lattice parameter, ac, at 2,683, 2,388, and 2,503 K result in 0.5269, 0.52438, and 0.5247 nm, respectively. The measurement at 2,683 K was done

Cubic ZirconiaFig. 2 Crystal structure of cubic zirconia as seen from the [153] direction

Table 1 General crystallographic correlations in cubic zirconia

Space group

Fm3m

Reflection conditions

hkl: h + k, k + l, l + h = 2n 0kl: k, l = 2n hhl: h + l = 2n h00: h = 2

Coordination number

8

Z

1

Lattice parameter

a

Unit cell volume

V = a3

Ionic positions

Zr4+: 4a O2-: 8c

Cubic Zirconiain a neutral atmosphere, while the latter two measurements were done in a reducing atmosphere [6]. At increasing pressures, the lattice parameter changes to 0.4947, 0.4925, and 0.4916 nm for pressures of 28.9, 33.8, and 37.3 GPa, respectively [7].