Phase analysis of sintered yttria-zirconia ceramics by x-ray
diffraction
A. Paterson
National Institute for Materials Research, CSIR, P.O. Box 395, Pretoria, South Africa
R. Stevens
Department of Ceramics, University of Leeds, Leeds LS2 9JT, England
(Received 13 November 1985; accepted 18 December 1985)
Determination of the amount of cubic and tetragonal phase in yttria-zirconia using high-angle
XRD (x-ray diffraction) has been complicated by problems of resolution and interpretation.
The evidence, from electron diffraction studies, for a
c-^-t
shear transformation also needs to be
taken into account. Two compositions, a 3 and a 5.7 mol % Y
2
O
3
-ZrO
2
, were sintered and
thermally treated at different temperatures between 1450° and 1700 °C. X-ray diffraction traces
revealed the anticipated tetragonal (400) and (004) reflections. The region of the diffraction
pattern that was thought to arise from the cubic phase could be best interpreted as a second
tetragonal phase
t'.
The original amount of cubic phase computed from the
t'
reflections showed
good agreement with the phase diagram of Scott. The lattice parameters of the
t'
phase were
determined, and the volume of the tetragonal
(t
') unit cell was calculated.
I. INTRODUCTION
Phase analysis of partially stabilized zirconias by x-
ray diffraction (XRD) using low-angle (111),.,,
(lll)
m
, and (lll)
m
reflections has permitted the
quantitative determination of monoclinic contents pres-
ent in a system.' The assumptions on which the calcula-
tions were made have been shown to be invalid, and a
detailed analysis of the problem has been made by Evans
et al.
2
For the low-angle determinations, a number of
alternative theoretical and experimental formulas are
now available.
2
^*
High-angle reflections have been used to determine
the relative proportions of the cubic and tetragonal
phase.
5
The most complete description of high-angle,
cubic-tetragonal analysis has been due to Miller
et al.
6
in
an investigation of plasma-sprayed, yttria-zirconia
coatings. The method used was based on the low-angle
analysis of Porter and Heuer
7
to derive an equation of
the form
M
c
= 0.88-
'(400)c
Mt
-"(400); + •'(004)1
where
M
c
and
M,
are the mole fractions of the cubic and
tetragonal phase, respectively, and the integrated inten-
sities / of the various reflections are indicated with the
appropriate Miller indices. In that study the cubic re-
flection was considered to be relatively composition in-
variant, and the angles of the reflections were standard-
ized for the (400)
c
reflection at 73.29°. The XRD
patterns were deconvolved and the
d
spacings of the
(400), and (004), reflections calculated. The angular
separation of the tetragonal reflections increased with
heat treatment as did the integrated intensity of the cu-
bic reflection. The interpretation of this information
suggested that the as-sprayed yttria-zirconia has a te-
tragonal phase of relatively high yttria content present,
which transforms to the expected tetragonal and cubic