REINVESTIGATION OF YTTRIA-TETRAGONAL ZIRCONIA POLYCRYSTAL (Y-TZP) BY NEUTRON POWDER DIFFRACTION - A CAUTIONARY TALE

In the re-investigation by neutron powder diffraction of 3 mol% yttria-tetragonal zirconia polycrystal (Y-TZP), it was realized that the sample, initially taken to be single-phase tetragonal zirconia, was in fact a two-phase mixture of the tetragonal (80%) and cubic (20%) polymorphs. Two-phase refinement gave for the tetragonal phase [P4(2)/nmc, a = 3.6008 (1), c = 5.1793 (1) Angstrom] the results z(O) = 0.4564(1), B-Zr,B-Y = 0.45(2) and B-O = 0.72 (2) Angstrom(2). Refinement on the basis of a single-phase tetragonal sample yielded values for the position and displacement parameters somewhat biased towards those pertaining to the cubic phase. The conclusions from previous studies have been re-examined in the light of the present work.