EFFECT OF HYDROXIDE CALCINATION TEMPERATURE,
COLD ISOSTATIC PRESSING (CIP) PRESSURE, AND SINTERING
TEMPERATURE ON PROPERTIES OF ZrO
+ 3 MOL.% Y
G. Ya. Akimov,
V. M. Timchenko,
and É. V. Chaika
Translated from Ogneupory i Tekhnicheskaya Keramika, No. 1, pp. 30 – 32, January, 2002.
+ 3 mol.% Y
ceramic specimens are prepared by sintering, at 1500 and 1600°C, preforms molded
from calcined hydroxide powders at 850 and 750°C using a cold isostatic pressing (CIP) technique. Bending
strength and density measured as a function of the CIP pressure is shown to be quite different for specimens
sintered at the two temperatures. Implications of this different behavior are discussed.
The most widespread method for preparation of ZrO
3 mol.% Y
powders (henceforth labeled ZY-3) is co-pre-
cipitation of hydroxides from aqueous solutions of zirconium
and yttrium salts . The subsequent operations involve cal-
cination of the washed and dried precipitate. Sintering gives
a substitutional solid solution. A temperature of 500°C is
high enough for synthesis of the solid solution; however,
sintering is normally carried out at about 1000°C. This high-
temperature regime allows the ZY-3 particle size to be in
creased from 5 – 10 nm (500°C) to 80 – 100 nm (1000°C)
. It was shown in earlier works [2 – 4] that cold isostatic
pressing (CIP) of oxide powders with particle size smaller
than a critical value can cause bulk plastic strain  or sur
face strain  which results in the formation of larger
polycrystalline aggregates. In powders subjected to CIP,
these aggregates form an intragranular arched structure .
Naturally, the occurrence of such a structure will affect the
densification and recrystallization at sintering and thus cause
a change in physicomechanical properties of the ceramic.
Our goal in the present work was to study the effect of
hydroxide calcination temperature, CIP pressure, and sin
tering pressure on the density and the three-point bending
of the ZY-3 ceramic.
The powders for testing were prepared by coprecipitation
from aqueous solutions of zirconium and yttrium chlorides.
Properly washed and dried, they were calcined at 850°C for
3.5 h (set 1 ) and at 750°C for 2 h (set 2 ). The calcined pow
ders were ground in a Sand planetary mill in water, dried,
and calcined at 600°C for 1 h. The powders thus prepared
were compacted into preforms by the method of  using a
UVD-1 hydrostat at a pressure not exceeding 0.8 GPa. The
preforms were ground on an ASV diamond grinding wheel
and then sintered at 1500 and 1600°C for 2 h in air. The
sintered specimens were ground on an ASV-type diamond
grinding wheel. The density of ceramic specimens was mea
sured by a hydrostatic weighing method and the strength was
determined by a three-point bending technique. The gauge
length in bending was 14.5 mm.
Relevant data are given in Fig. 1 (set 1 ) and Fig. 2
(set 2 ). Bending strength and density measured as a function
of the CIP pressure for specimens of the two sets show a ba
sically different behavior. In the set 1 specimens, the density
r and bending strength s
increase with pressure, whereas in
the set 2 the opposite trend is observed.
To be able to design a qualitative model that would relate
the density and bending strength to CIP pressure and sin
tering temperature, one will want to know in what way the
structure of compact is affected by the conglomerate tough
ness and the properties of finished ceramic — by the sin
As is well known, ultradisperse powders are capable of
forming conglomerates whose strength increases substan
tially with an increase in dispersivity. With a decrease in oxi
de calcination temperature, the powder dispersivity in
creases, that is, the toughness of conglomerate improves.
During the CIP, the conglomerate forms an arching structure
Refractories and Industrial Ceramics Vol. 43, Nos.1–2, 2002
1083-4877/02/0102-0029$27.00 © 2002 Plenum Publishing Corporation
A. A. Galkin Institute of Engineering Physics, National Academy
of Sciences, Donetsk, Ukraine.