Yttria-stabilized zirconia (YSZ) is one of the most studied metal oxides [1–4]. It is a relatively hard and chemically inert material. YSZ is characterised by wear resistance, high-temperature stability and corrosion resistance, superionic conductivity at high temperature. The material is mostly used in jet engines, to determine oxygen content in exhaust gases, to measure pH in high-temperature water, as membranes for high temperature solid oxide fuel cell, as a component of waveguides and laser mirrors, and optical filters, as well as for electrolytes or insulators in microelectronic devices.

Several zirconia polymorphs are known (monoclinic, tetragonal, cubic and rhombohedral one). Among them, those of the highest symmetry are of most interest, due to their attractive properties. To prepare the desired cubic or tetragonal phase, thermal treatment and/or doping with yttrium or other dopants are typically used.

Nanocrystalline zirconium dioxide powder samples were characterized by X-ray diffraction using a Philips X'pert MRD diffractometer. The changes in ZrO₂ structure and microstructure due to annealing and yttrium doping were studied. Rietveld analysis, done by FullProf, based on the structure of the component phases [5] was used for quantitative phase analysis and structure refinement. In this work, the phase composition and structure of Zr_0.9214Y_0.0712Pr_0.0074O_1.9607 (sample A) and Zr_0.8962Y_0.0958Pr_0.0080O_1.9481 (sample B) prepared by treatment at two temperatures, 70^oC and 1200^oC, was studied and compared with ZrO₂ structure.

The unannealed undoped sample contains the tetragonal (78%) and monoclinic (22%) phases. An addition of yttria results in disappearing of the minority monoclinic component. Moreover, the axial ratio of the tetragonal phase shows a clear decreasing tendency. The changes in the structure, phase composition and crystallite size caused by addition of yttria, Pr doping and annealing will be discussed.

References

[1] J. Ciosek, W. Paszkowicz, P. Pankowski, J. Firak, U. Stanislawek, Z. Patron, Vacuum 72 (2004) 135–141

[2] A.C.T. van Duin, B.V. Merinov, S.S. Jang, W.A. Goddard III, J. Phys. Chem. A 112 (2008) 3133–3140

[3] K. Muraoka, Appl. Phys. Lett. 80 (2002) 4516–4518

[4] C. Piconi, G. Maccauro, Biomaterials 20  (1999)  1–25

[5] ICSD database (Karlsruhe 2008) 

Figure 1.  Experimental x-ray diffraction patterns of zirconia. The vertical bars show the peak positions for the tetragonal phase (upper) and monoclinic phase (lower).