Sinterability and decomposition of Pb0.9175La 0.055Zr0.975Ti0.025O3: Influence of calcination and sintering temperature

Article abstract of DOI:10.1111/j.1551-2916.2007.01724.x

The sinterability and decomposition of PLZT, (Pb,La)(Zr,Ti)O3, depend on the temperature and soaking time of both the calcination and sintering temperature. They were determined from the density, linear shrinkage, weight loss, and appearance of extra phases. At moderate calcination temperatures and times, there is no escape of PbO from the PLZT. At calcination temperatures higher than 1050°C and soaking times above 3 h, PbO escapes, and ZrO2 and La2Zr2O7 can be detected. Even when sintered in a PbO-rich atmosphere, some PbO evaporates during sintering either from free PbO or from the PbO bound in the PLZT in regions in the outer surfaces of the sintered body. An aggressive depletion of PbO during sintering can result in a complete disappearance of the grain boundary phase, giving an intragranular fracture.

Full text of DOI:10.1111/j.1551-2916.2007.01724.x

J. Am. Ceram. Soc., 90 [7] 2043–2049 (2007)
DOI: 10.1111/j.1551-2916.2007.01724.x
r 2007 The American Ceramic Society
ournal
J
Sinterability and Decomposition of Pb0.9175La0.055Zr0.975Ti0.025O3:
Influence of Calcination and Sintering Temperature
,w
Else Breval, Maria Klimkiewicz, Chiping Wang, and Joseph P. Dougherty*
Materials Research Institute, Penn State University, University Park, Pennsylvania 16802
Ann Crespi
Medtronic Energy & Component Center, Brooklyn Center, Minnesota 55430
The sinterability and decomposition of PLZT, (Pb,La)(Zr,Ti)
O , depend on the temperature and soaking time of both the
(2) Sinterability
3
Sinterability can be described as the ability to obtain a density
near the theoretical density, which is often related to the linear
shrinkage. To ensure a high density, extra PbO is added to the
calcination and sintering temperature. They were determined
from the density, linear shrinkage, weight loss, and appearance
of extra phases. At moderate calcination temperatures and
times, there is no escape of PbO from the PLZT. At calcina-
tion temperatures higher than 10501C and soaking times above 3
1
–4
formula to avoid PbO depletion during sintering. PbO has a
melting point at 8881C and therefore a high vapor pressure at
sintering temperatures. For these reasons, there is a relatively
large amount of liquid PbO grain boundary phase. The sintering
process can therefore be categorized as sintering with a reactive
h, PbO escapes, and ZrO and La Zr O can be detected. Even
2
2
2
7
when sintered in a PbO-rich atmosphere, some PbO evaporates
during sintering either from free PbO or from the PbO bound in
the PLZT in regions in the outer surfaces of the sintered body.
An aggressive depletion of PbO during sintering can result in a
complete disappearance of the grain boundary phase, giving an
intragranular fracture.
5
liquid. This type of sintering generally results in a rapid dens-
ification if (i) there is an appreciable amount of the liquid phase,
if (ii) there is an appreciable solubility of the solid in the liquid,
and if (iii) the solid is wetted by the liquid. The first criterion is
fulfilled as an excess of PbO is added to the formula. The second
criterion is also met. See Phase diagrams by Fushimi and Ikeda
and by Warzee et al., which show that the solubility of PbZrO
6
7
3
in PbO varies from 3 to 6 wt% when going from 11001 to
I. Introduction
3
13001C. The corresponding numbers for PbTiO in PbO are 50–
100 wt%. When La O is also present, the solubility of PbZrO
and PbTiO
(
1) Composition and Structure
2
3
3
7
–9
3
becomes even higher.
Finally, ceramic grain
HE PLZT, (Pb,La)(Zr,Ti)O , is a useful material for pulse
3
5
boundary phases, in this case PbO, generally wet well, result-
ing in a high capillary pressure. These three criteria are respon-
sible for the rearrangement of particles, dissolution, and
recrystallization of solid PLZT at contact points toward a
more effective packing, before a solid skeleton is formed at
which time the densification process stops. When pressing pow-
der into a pellet, the green density generally becomes denser in
the exterior. Therefore, pressed bodies have a tendency to have a
larger firing shrinkage in the interior than in the outer parts near
T
discharge multilayer capacitors due to the capability of stor-
1
ing and releasing large amounts of energy, especially for the
antiferroelectric orthorhombic PLZT phase for LoB0.08 and
ToB0.075. In our notation, a PLZT composition is designated
L/Z/T, indicating the amount of lanthanum, zirconium, and ti-
tanium in the structure. For example, the composition Pb1À3x/2
x
La Zr
Ti1ÀyO
y 3
is written as 100x/100y/100(1Ày).
PLZT has a perovskite ABO structure and is a crystalline
3
solution system with La substitution for Pb and Ti substitution
for Zr in the PbZrO . On substituting La for Pb, vacancies are
3
introduced into the lattice, and when sintered in excess of PbO,
only B-site vacancies occur in the so-called B-site formula:
5
the surface. Shrinkage also occurs via diffusion of oxygen va-
cancies from the pores to the outer part of the sample, but this
3
1
process is comparatively very slow. One of the purposes of this
work was to study the densification and linear shrinkage of the
Pb1ÀxLa
x
(Zr
y
Ti1Ày
)
1Àx/4
O
3
, and only A-site vacancies can oc-
Zr . It has been
5.5/97.5/2.5 PLZT during sintering.
cur in the A-site formula: Pb1À3x/2La
x
y
Ti1Ày
O
3
2
stated that PLZT materials often have compositions between
the A and B formulas. However, the A site predominates be-
cause the PbO partial pressure, necessary to produce a B for-
mulation, is limited by the condensation of liquid PbO at the
grain boundaries. Land et al. stated that for Lr5%, only A
compositions could exist. In the present study, the La concen-
tration of 5.5% is not far from this limit, and in the present
study of 5.5/97.5/2.5, the raw materials were prepared using the
A formulation and, after sintering, were considered to be the A
composition (the A-site vacancy formulation).
(
3) Thermal Decomposition
The decomposition of PLZT is a measure of how much PbO
evaporates from the PLZT during heating. As explained above,
the evaporation of PbO into the surroundings was controlled by
adding extra PbO to the formula. Extensive efforts have been
made to establish an appropriate atmosphere to allow the excess
PbO to flow out without PbO disappearing from the PLZT
3
4
3
,4
¨
phase. A fundamental work was carried out by Hardtl and
1
0
Rau, who determined the vapor pressure of PbO for pure PbO
and of various PZT compositions, for different temperatures.
Atkin and Fulrath determined which powder mixtures of PZ,
E. Suvaci—contributing editor
3
2
PZT, PT, ZrO , and PbO should be used to allow the PZT
specimen to equilibrate with the powder to prevent PbO loss
from the PZT structure. If, after sintering, there is still some
PbO left in the grain boundary phase, it is possible to anneal to a
temperature just high enough to allow the PbO to evaporate
Manuscript No. 21701. Received April 13, 2006; approved November 8, 2006.
This work was financially supported by Medtronic, Energy & Component Center,
Brooklyn Center, MN 55430.
*
Member, The American Ceramic Society.
w
11,12
11
Author to whom correspondence should be addressed. e-mail: jxd6@psu.edu
without losing PbO from the PZT phase.
Xia and Yao and
2
043

2
044
Journal of the American Ceramic Society—Breval et al.
pointed out that it was also possible to (2) Characterization Methods
Vol. 90, No. 7
1
3,14
Kingon and Clark
establish an excess PbO vapor pressure in the surrounding at-
mosphere during sintering. This excess produced lower densities
when using a high PbO pressure in the sintering atmosphere. It
is important that the powder for maintaining the PbO atmo-
X-ray diffractometry (XRD) of powder was carried out on
an automated X-ray powder diffractometer PAD V, Scintag
(
Santa Clara, CA), using CuKa radiation and l 5 1.540598
˚
A. Powders from crushed pellets were used to ensure average
results from the entire pellet. The intensity of each X-ray phase
is calculated as the intensity of the strongest peak of this
phase normalized to the strongest peak in the entire spectrum.
For small batches (5 g), the entire sample was used for X-ray
diffraction. For a large sample (6 kg), the sample is powder from
the top, middle, and bottom of the crucible.
1
3,14
sphere is not in contact with the sintering sample
unless it
has exactly the same composition as the sample, as Ti can dif-
fuse either way depending on the concentrations of Ti in the
powder and the sintering body.
The migration of PbO from a PZ structure during sintering
By creating a low-PbO envi-
1
5,16
was investigated by Northrob.
ronment during sintering, a PbO depletion of the surface
occurred. The depletion of PbO took place in two stages:
SEM/EDS (Hitachi S-3500N/EDS PGT, Tokyo, Japan)
techniques were used to study morphology and element deter-
mination and distribution to visualize phases, including those
that were in too small amounts to be detected by XRD.
The loss on ignition at 10001C for 30 h of raw materials ex-
cept PbO was determined. For PbO, the test temperature was
(
diffuse-controlled migration of Pb from the PZ lattice. A
1) a quick evaporation of free PbO, (2) followed by a slow
1
1
similar experiment carried out by Xia and Yao showed that
Pb(Zn1/3Nb2/3)O sintered in an atmosphere containing suffi-
3
cient PbO experienced an intergranular fracture, presumably
because of the PbO in the grain boundary, whereas the PbO-
depleted structure was porous and had an intragranular frac-
ture. When La was substituted for Pb in the PZT structure, it
7
ing the powder before and after calcination.
Weight loss was also determined for the sintering of the pel-
lets. The density and linear shrinkage during sintering were de-
termined by weighing the pellets and measuring the dimensions.
001C. Weight loss during calcination was established by weigh-
1
7
was found that ZrO and/or La Zr O could be formed. How-
2
2
2
7
2 2 7
ever, the presence of La Zr O may not necessarily be a sign of
PbO depletion; it could also be caused by a low temperature
1
7
during sintering. Further heating would then make La Zr O
7
2
2
III. Results and Discussions
disappear. The second purpose of the present study was to
explore the decomposition of an antiferroelectric PLZT phase
(1) Calcination: Temperature, Time, and Batch Size as
Parameters
(5.5/97.5/2.5) at different calcination and sintering temperatures.
Table I and Fig. 1 describe the calcination of 5 g of powder when
calcined for 3 h at temperatures from 4001 to 10501C. The
weight loss and phase changes were followed by 501–1001C in-
tervals. A major part of the weight loss occurred between 5501
and 7001C; PLZT was formed between 6501 and 7001C. At
higher temperatures, small amounts of free PbO appeared, but
disappeared again at 9001C. The XRD reflections of the free
PbO showed that this phase was PbO1.55 (ICDD 27-1200),
indicating a Pb O structure with Pb vacancies. La Zr O
II. Experimental Procedure
(
1) Materials: Synthesis and Heating
Raw materials for PLZT powder with the composition 5.5/97.5/
.5 were weighed off as the A composition with 2.5 wt% extra
2
1
8,19
PbO as described earlier.
Small batches (5 g) were calcined
up to the calcination temperature ranging from 4001 to 10501C
with a heating ramp of 71 to 81C/min and a soaking time from 3
to 24 h. Large batches (6 kg) were calcined with a heating ramp
of B11C/min up to 875–10501C with a soaking time from 2 to 4
h. A total acceptable weight loss during calcination would be 0.5
wt% from adsorbed water in the raw La O material. If some of
2 3
the extra PbO was lost too, an additional 2.5 wt% loss could
stem from the extra PbO.
2
3
2
2
7
appeared only for high calcination temperatures (10501C) and
long soaking times (ꢀ 12 h). At that time, all the free PbO had
evaporated, together with some of the PbO from the PLZT
phase. Figure 1 depicts the weight loss as a function of temper-
ature and time. The reason for the limited weight losses is that
PLZT was formed between 6501 and 7001C, binding most of the
free PbO into the PLZT structure. Figure 1 shows that only very
little free PbO, and no PbO from the PLZT phase can evaporate
within 24 h at temperatures below 10001C in the small batches
tested. At 10501C, PbO in PLZT can only evaporate after about
7.5 h, at which time 3% (0.5% from OH groups from the La O
For sintering, the calcined powder was crushed in a mortar,
sieved through a 100-mesh sieve, 471 wt% binder was added,
and the powder was again sieved through a 100-mesh sieve.
Pellets of 12.5-and 25-mm diameter and 2-mm thickness were
2
3
2
pressed at a pressure of 20 N/m . Binder burn-out was carried
out in air with a ramp rate of RT to 3501C in 150 min, held at
and 2.5% from the extra PbO) would have evaporated. Most
industrial calcination times would be 2–3 h, ensuring no evap-
oration of PbO from the PLZT.
3
501C for 120 min, ramped up from 3501 to 5501C in 120 min,
and held at 5501C for 60 min. The sintering was carried out in
covered crucibles in air at 12701 or 13001C for 2 h at a ramp-up
of 101C/min. The maximum firing temperature was frequently
monitored by placing a so-called Tempring (Bickley, Bensalem,
PA) on top of the covering crucible. A protective atmosphere
was established by placing a boat with fresh PbO source powder
inside the crucible during the sintering. The covers did not
fit airtight; therefore, PbO can disappear out of the crucible
through the gap between crucible and cover. In no case did a
significant amount of PbO source powder disappear during the
sintering. An acceptable weight loss during binder burn-out and
sintering would then stem from: (i) extra PbO if still remaining
Table II shows the calcination of 6 kg of powder when cal-
cined at different calcination schedules. The weight loss was only
determined for a few of the experiments. It can be seen that the
weight loss, as expected, is slightly less than when using 5-g
batches, as shown in Table I. The phase distribution varies
somewhat between the experiments. The reason may be due to
difficulties with taking average powder samples from the 6-kg
batch. Second phases can appear in the batches, small amounts
of ZrO , and larger amounts of PbO
2
1.55
2 2 7
and La Zr O . These
phases did not show up in the small batches when using the same
calcination schedules. Table III shows a comparison between
small (5 g) and large (6 kg) batches. The second phases for the
large batches are calculated as averages from Table II. The rea-
son for the differences between small and large batches of same
calcination schedule is not clear.
(2.5 wt%), and (ii) binder burn-out (471 wt%).
That would give a total of max 6.571 wt% sinter weight loss.
In one experiment, a sintering atmosphere of insufficient PbO
was produced by placing a Tempring inside the crucible instead
of the PbO source powder. The Tempring is very porous and
able to absorb large amounts of PbO and thereby produce a
PbO-deficient-sintered pellet. In another experiment, an attempt
was made to create a dense PbO grain boundary phase by im-
pregnating a pellet with Pb(NO ) before sintering in air.
(2) Sintering: Calcination, and Sintering Conditions as
Parameters
In one sintering experiment, two of the large-batch powders were
used: one calcined at 9501C/2 h, and the other at 10501C/3 h.
3
2

July 2007
Sinterability and Decomposition of Pb0.9175La0.055Zr0.975Ti0.025O3
2045
Table I. Weight Loss and XRD Phases from 5-g Batches of Raw PLZT 5.5/97.5/2.5 after Different Calcination
Temperatures and Times
Calcined
X-ray phases
temperature/
Weight
time (1C/h)
loss (wt%)
ZrO
2
(i%)
PbO
L
(i%)
PbO
M
(i%)
La O
2 3
(i%)
La(OH)
3
(i%)
TiO
2
(i%)
PLZT (i%)
PbO1.55 (i%)
2 2 7
La Zr O (i%)
Uncalcined
0
23.01
20.65
16.13
12.77
12.23
0
0
0
0
0
0
16.48
20.11
18
3.2
0
0
0
0
0
100
100
100
100
100
0
0
0
0
0
0
0
0
100
0
0
0
0
100
0
0
0
0
100
0
0
0
0
100
0
3.80
3.80
3.80
3.26
3.26
0
0
0
0
0
0
0
0
3.80
0
0
0
0
3.80
0
0
0
0
3.80
0
0
0
0
3.80
0
0
1.09
0
0
0
0
0
0
0
0
0
0
0
0
1.09
0
0
0
0
1.09
0
0
0
0
1.09
0
0
0
0
Trace
Trace
Trace
Trace
0
0
0
0
0
0
0
0
0
1.06
4.79
3.61
3.11
1.79
0.62
0
0
0
0
0.62
0.10
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
4
5
6
6
7
7
8
8
9
9
1
1
00/3
00/3
00/3
50/3
00/3
50/3
00/3
50/3
00/3
50/3
000/3
050/3
1.06
1.08
1.34
1.38
1.64
1.65
1.71
1.71
1.73
1.72
1.81
1.93
0
1.73
1.76
1.77
1.85
0
1.72
1.76
1.86
1.87
0
0
0
0
0
0
0
0
0
100
100
100
100
100
100
100
100
0
100
100
100
100
0
100
100
100
100
0
100
100
100
100
0
0
0
0
0
0
23.01
0
0
0
0
23.01
0
0
0
0
16.48
0
0
0
0
16.48
0
0
0
0
16.48
0
0
0
0
16.48
0
0
0
0
Trace
Uncalcined
9
9
9
9
00/3
00/6
00/12
00/24
0
0
0
0
Trace
Uncalcined
9
9
9
9
50/3
50/6
50/12
50/24
0
0
0
0
0
0
0
0
0
0
0
0
0
Trace
Uncalcined
23.01
0
0
1
1
1
1
000/3
000/6
000/12
000/24
1.81
1.87
2.05
2.56
0
1.93
2.46
4.23
0
0
0
0
1.78
23.01
0
2.14
0
0
Trace
Uncalcined
1.09
0
0
1
1
1
050/3
050/6
050/12
0
0
0
100
100
100
0
0
0
0
0
0
0
3.61
The intensity of each X-ray phase is given as the intensity of the strongest peak of this phase normalized to the strongest peak in the entire spectrum (i%). PbO
L
(litharge).
PbO (massicot). PbO1.55 (near Pb structure). PLZT, (Pb,La)(Zr,Ti)O
M
2
O
3
3
.
The sintering took place side by side in the same sintering
experiment. See Table IV and Figs. 2 and 3 for details.
The powder calcined at 9501C for 2 h did not contain a sec-
ond phase. However, La Zr O appeared on sintering at 900–
Table II. Effect of Different Calcination Schedules in Air
X-ray data
Temperature/
Weight
2
2
7
time (1C/h)
loss (wt%)
ZrO
2
(i%)
PbO1.55 (i%)
2 2 7
La Zr O (i%)
1
2001C, and above 12001C, it disappeared; it probably dissolved
17
in the PLZT as predicted by Schulze et al. However, above
3001C, some of the PLZT disintegrated, and ZrO was formed.
8
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
1
1
75/4
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2w
50/2
50/2
50/3
50/3
50/3
050/3
050/3w
1.56
1.51
1.50
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
1.75
N/A
0.94
0.5
0.2
0
0
0
0
0
0
0
1.93
2.76
0.4
0.76
2.27
2.38
5.29
0
1.15
1.69
0
0
0
1.33
3.84
0.05
0
2.27
0
2.87
0
3.33
0
0
0
0
4.39
0
1
2
0
0
1.44
0
1.15
1.0
0
1.0
3.68
3.37
1.82
0
0
4.89
5.88
0
Phase distribution of PLZT 5.5/97.5/2.5 with 6 kg batches. The intensity of
each X-ray phase is given as the intensity of the strongest peak of this phase nor-
malized to the strongest peak (PLZT) in the entire spectrum (i%). wThe batches
Fig. 1. Weight loss after calcination (5-g batch) at 9501, 10001, and
0501C.
1
3
were used for the experiments shown in Table IV. PLZT, (Pb,La)(Zr,Ti)O .

2
046
Journal of the American Ceramic Society—Breval et al.
Table III. Effect of Batch Size
Vol. 90, No. 7
Calcined
X-ray data
temperature/
time (1C/h)
Batch
amount (g)
ZrO
2
(i%)
PbO1.55 (i%)
2 2 7
La Zr O (i%)
8
8
9
9
9
9
1
1
75/4
75/4
50/2
50/2
50/3
50/3
050/3
050/3
5
6000
5
6000
5
6000
5
6000
0
0.9
0
0.2
0
0.7
0
1.2
1.9
0
1.3
0
2.7
0
0.9
0
1.3
0
1.0
0
1.5
0
0
5.4
Phase distribution of PLZT 5.5/97.5/2.5 when calcined with different calcina-
tion schedules in air. The 6-kg batches are calculated as an average from Table II.
The intensity of each X-ray phase is given as the intensity of the strongest peak
(
PLZT) of this phase normalized to the strongest peak in the entire spectrum (i%).
PLZT, (Pb,La)(Zr,Ti)O
3
.
At 14001C, further PbO weight loss from the PLZT phase gave a
high total weight loss of 17.92 wt%, a low density, and a linear
shrinkage slightly higher than that at 13001C. The powder cal-
Fig. 3. Density, shrinkage, and weight loss as a function of weight loss
for PLZT 5.5/97.5/2.5 calcined at 10501C/3 h (6 kg, large batch).
2 2 7
cined at 10501C for 3 h contained La Zr O , but this also dis-
solved in the PLZT when sintered above 12001C as predicted by
Table IV. Effect of Sintering Temperature
1
7
Schulze et al. No foreign X-ray-detected phases appeared even
when sintered at 14001C, which gave a linear shrinkage that was
nearly the same as found when sintered at 13001C. The density
Sintering data
Extra X-ray phases
Calcined
temperature/ temperature/
time (1C/h) time (1C/h) (% of theor.) (%) loss (wt%) (i%)
Sintered
Density Shrinkage Weight La
Zr
2 2
O
7
ZrO
2
(
7
when sintered at 14001C) was high and the weight loss was only
.56 wt%. This is only a fraction larger than the threshold value
(i%)
of B6.571 wt% stemming from loss of binder phase and extra
PbO, indicating that only a relatively small amount of PbO from
the PLZT evaporated. Figures 2 and 3 show that there is a close
relationship between density, shrinkage, and weight loss, except
at a sintering temperature of 14001C for the powder calcined at
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
9
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
50/2
Unsintered
700/2
750/2
800/2
850/2
—
—
0
0
0
—
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
51.7
52.2
52.2
53.2
52.4
58.2
64.2
67.0
66.5
70.7
75.2
82.3
90.8
93.4
94.7
80.8
—
57.4
58.5
60.0
65.5
65.6
66.2
63.9
65.7
66.5
70.5
78.3
90.9
90.1
92.1
95.8
93.5
0.11
0.11
0.09
0.16
0.38 1.19
0.50 1.09
1.62 3.98
1.71 3.53
1.77 4.60
1.93 2.50
2.10 1.14
0.17
1.24
2.07
5.14
6.61
7.54
8.84
10.57
15.78
17.53
17.91
18.75
19.98 17.92
—
2.13
2.61
3.72
6.35
6.73
9
501C. At this high temperature, an exceptionally large weight
900/2
950/2
loss occurred.
The only difference between the two powders is that the pow-
der calcined at 10501C contains La Zr O , whereas the powder
2 2 7
calcined at 9501C does not. To compare the two calcined pow-
ders, the samples sintered at 13001/2 h were further investigated
in the SEM. To avoid artifacts from any polishing agent, the
samples were fractured, and both the interior and the exterior
parts were studied. According to Table IV, both samples had no
foreign phases detected by the XRD, and the same shrinkage.
1000/2
1050/2
1100/2
1150/2
1200/2
1250/2
1270/2
1300/2
1350/2
1400/2
2.47
2.84
3.06
5.67
0
0
0
0
0
5.88
1.35
11.63
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
050/3 Unsintered
050/3 700/2
050/3 750/2
050/3 800/2
050/3 850/2
050/3 900/2
050/3 950/2
050/3 1000/2
050/3 1050/2
050/3 1100/2
050/3 1150/2
050/3 1200/2
050/3 1250/2
050/3 1270/2
050/3 1300/2
050/3 1350/2
050/3 1400/2
—
0.11 5.29
0.16 5.88
0.19 5.61
0.70 4.48
0.60 5.60
1.72 5.37
2.90 5.37
3.03 5.24
3.46 4.06
3.84 3.93
4.22 1.33
4.53
4.74
4.43
7.25
7.56
8.02
8.84
9.49
10.21
12.04
15.09
17.44
17.74
17.98
18.28
18.31
0
0
0
0
0
0
0
Sintering using large batches of PLZT 5.5/97.5/2.5 powder calcined at 9501C/
h, 10501C/3 h, respectively. The density (in % of theoretical density) and shrink-
2
age (linear reduction of the sintered pellet, i.e. sintered diameter in % of the green
diameter) are a measure of the sinterability. The intensity of each X-ray phase is
given as the intensity of the strongest peak of this phase normalized to the strong-
est peak in the entire spectrum (i%). No PbO1.55 was found in any of the samples.
Fig. 2. Density, shrinkage, and weight loss as a function of weight loss
for PLZT 5.5/97.5/2.5 calcined at 9501C/2 h (6 kg, large batch).
3
PLZT, (Pb,La)(Zr,Ti)O .

July 2007
Sinterability and Decomposition of Pb0.9175La0.055Zr0.975Ti0.025O3
2047
Fig. 4. PLZT 5.5/97.5/2.5 calcined at 9501/2 h (6 kg, large batch) and
sintered at 13001C/2h. SEM image: fractured cross section with top sur-
face to the right.
Fig. 6. PLZT 5.5/97.5/2.5 calcined at 10501C/3 h (6 kg, large batch)
and sintered at 13001C/2 h with a loss of 4.4 wt%. SEM image: fractured
cross section with top surface to the right.
The weight loss was slightly smaller and the density slightly
larger for the sample made from the powder calcined at 9501C.
This sample (Figs. 4 and 5) was homogeneous almost to the
edge, but had more porosity in the interior than the sample sin-
tered from the powder calcined at 10501C (Figs. 6 and 7), which
showed different-looking regions in the upper B50 mm of the
surface. These regions were Pb-deficient and Zr-rich. The very
upper B10 mm contained large amounts of La. This indicates
evaporation of PbO from PLZT near the edge. For this sample,
the larger weight loss indicates that more PbO must have evap-
orated, some of which may be free PbO from the grain bound-
aries and some may be PbO from the PLZT near the edge. The
difference in sintering behavior between the two powders can be
seen in Figs. 2 and 3. At sintering temperatures below B12001C,
2 2 7
when La Zr O is present (in the sample from powder calcined
7
–9
at 10501C), it can dissolve in free PbO. This leads to a lower
temperature for the formation of a liquid grain boundary phase,
together with a larger volume of grain boundary phase. There-
Fig. 7. PLZT 5.5/97.5/2.5 calcined at 10501C/3 h (6 kg, large batch)
and sintered at 13001C/2 h. X-ray dot map from the area seen in Fig. 6.
Zr-rich, Pb-deficient regions are visible. The top surface contains a La-
rich phase.
5
by, the formation of the skeleton is delayed, resulting in a high-
er densification and shrinkage at low sintering temperatures.
There may be a connection to the PbO effect as explained by
1
3,14
Kingon and Clark.
They found that a large amount of a
The effect of soaking time for sintering at 13001C is shown in
Fig. 8. As expected, a short soaking time results in poor densi-
ties, a low linear shrinkage, and low weight losses. Different
soaking times show that optimum sintering in terms of density,
linear shrinkage, and weight loss is already obtained at a soak-
ing time of about 50 min, after which there are no major chang-
es. However, an extended soaking time of 200–240 min can lead
to further weight loss (see Fig. 8).
PbO-rich liquid phase increases the rate of densification in the
initial and intermediate stages, but lowers the final density. The
skeleton of PLZT may be formed at a lower temperature in the
5
2 2 7
powder calcined at 9501C (without La Zr O ). This is in agree-
ment with the higher porosity in this sample. Therefore, the free
PbO in the grain boundaries may more easily evaporate from
the interior during the sintering rather than PbO from the
PLZT.
Fig. 5. PLZT 5.5/97.5/2.5 calcined at 9501/2 h (6 kg, large batch) and
sintered at 13001C/2 h. Element X-ray dot map from the area seen in
Fig. 4.
Fig. 8. Density, shrinkage, and weight loss after sintering of PLZT 5.5/
97.5/2.5 (calcined 9501C/3h, 6 kg, large batch) sintered at 13001C up to
240 min.

2048
Journal of the American Ceramic Society—Breval et al.
Table V. Effect of Pellet Diameter
Vol. 90, No. 7
Sintering
Volume/
Weight
loss
temperature/ Radius Height surface
À1
Density
Shrinkage
(%)
time (1C/h)
(mm)
(mm)
(mm
)
(% of theor.)
(wt%)
1
1
300/2
300/2
12.2
6.1
2
2
0.75
0.60
93.3
94.9
17.30
13.19
4.58
4.31
Sintering using large batches of PLZT 5.5/97.5/2.5 powder calcined at.9501C/3
h. Effect of pellet diameter. The density (in % of theoretical density) and shrinkage
linear reduction of the sintered pellet, i.e. sintered diameter in % of the green
diameter) are here used to describe the sinterability. PLZT, (Pb,La)(Zr,Ti)O
(
3
.
(
3) Sintering: Pellet Size as a Parameter
The effect of pellet size is shown in Table V. Two pellets, both
-mm thick, with 12.2- and 6.1-mm diameter, have nearly the
2
same density and weight loss. The green density of the smaller
pellet was 56.2% of the theoretical value, and the larger pellet
53.4%. Only slightly higher density and slightly smaller weight
loss indicate slightly better sinterability in the smaller diameter
pellet. However, there is a significantly larger linear shrinkage in
the 12.2-mm pellet. The reason can be explained by the smaller
5
compression of interior material during pressing leading to
larger shrinkage in the pellet with more interior material relative
to the exterior material (see Table V). The linear shrinkage is
therefore an ambiguous measure of the sinterability when using
pellets of the same size, pressed, and sintered in the same way.
(
4) Sintering: PbO Environment as a Parameter
The effect of PbO environment in the sintering atmosphere was
studied. A PbO-deficient atmosphere was created by placing a
Tempring inside the crucible instead of the PbO source powder.
The Tempring is very porous and able to absorb large amounts
of PbO and thereby produce a PbO-insufficient sintered pellet.
Also, an experiment with Pb salt impregnation was performed
Fig. 9. SEM image of the fractured surface of PLZT 5.5/97.5/2.5. (a)
Regular sintering in a covered crucible containing PbO source powder.
(
b) PbO-deficient sintering atmosphere.
3 2
by impregnating the pellet with a Pb(NO ) solution before the
regular sintering. The idea was to introduce PbO evenly around
the particles to use PbO as a sintering aid. These two samples
were compared with a regularly sintered sample. Table VI shows
that there is nearly the same linear shrinkage for all three sam-
ples. There was only small difference between the normal PbO
PNZ samples sintered in surplus of PbO and intragranular frac-
ture in samples sintered with a deficiency of PbO. Table VII
shows EDS results of fractured surfaces in the interior of the
samples sintered in a normal and in a deficient PbO atmosphere
as can be seen in Fig. 9. In the latter, some PbO had escaped,
3 2
pressure samples and the Pb(NO ) -impregnated sample in
leading to a larger ZrO content.
2
terms of density and weight loss, and both samples were phase
pure. However, for the low PbO pressure sample, the density
was significantly lower and the weight loss was significantly
higher, and was linked to the appearance of ZrO
2
as an indicator
Table VII. EDS Quantitative Analyses of the Fractured Sur-
face Areas Representing the Composition of the Interiors of a
Regular and a PbO-Deficient Pellet Described in Table VI
of escape of PbO. A more detailed study was performed on the
samples sintered in a normal and PbO-deficient atmosphere.
Figure 9 shows SEM images of fractured surfaces of the two
pellets. The pellet in the normal PbO atmosphere (Fig. 9(a))
showed an intergranular fracture, indicating that the grain
boundary phase is weaker than the PLZT grains. The pellet in
the PbO-deficient atmosphere (Fig. 9(b)) showed an intragran-
ular fracture. This is in agreement with the results of Xia and
Sintering (wt%)
Normal PbO pressure
Low PbO pressure
PbO
La O3
68.0
4.4
61.3
4.4
2
ZrO2
TiO
2
26.9
0.7
33.4
0.9
1
1
Yao, who found a tendency toward intergranular fracture in
Table VI. Effect of PbO Environment During Sintering Using Large
Batches of PLZT 5.5/97.5/2.5 Powder Calcined at 9501C/3 h
Sinter data
Extra phases
ZrO (i%)
PbO environment
Density (% of theor.)
Shrinkage (%)
Weight loss (wt%)
La Zr O
2 2 7
(i%)
2
PbO1.55 (i%)
Low PbO pressure
Normal PbO pressure
Pb(NO ) impregnated
89.0
93.4
95.0
17.74
17.53
17.20
11.83
4.49
4.64
0
0
0
2.25
0
0
0
0
0
3
2
Sintered at 13001C/2 h at three different PbO environments: below normal PbO pressure (Tempring inside the crucible), normal PbO level (regular sintering), and with PbO
sintering aid (pellet impregnated with Pb(NO ). The density (in % of theoretical density) and shrinkage (linear reduction of the sintered pellet, i.e. sintered diameter in % of the
green diameter) are used to describe the sinterability. Decomposition is described by weight loss above 6.5 wt% and the formation of new phases from the PLZT. The intensity of
each X-ray phase is given as the intensity of the strongest peak of this phase normalized to the strongest peak in the entire spectrum (i%). PLZT, (Pb,La)(Zr,Ti)O
3 2
)
3
.

July 2007
Sinterability and Decomposition of Pb0.9175La0.055Zr0.975Ti0.025O3
2049
5
W. D. Kingery, H. K. Bowen, and D. R. Uhlmann, pp. 209–16, 498–513.
Introduction to Ceramics. Wiley-Interscience Publication, John Wiley & Sons,
New York, 1976.
IV. Conclusions
On calcining raw materials for 2 h at temperatures up to 10501C
for 5.5/97.5/2.5, the PLZT structure appears from 6501 to
001C. The weight loss remains well within the margin of extra
6
2 2
S. Fushimi and T. Ikeda, ‘‘Phase Equilibrium on the System PbO–TiO –ZrO ,’’
J. Am. Ceram. Soc., 50 [3] 131 (1968).
M. H. Warzee, M. Maurice, F. Halla, and W. R. Ruston, ‘‘Phases in the
7
7
PbO added to the formula.
Minor phases may appear after the calcination. The presence
Binary System PbO–La O –Gd O , and Sm O ,’’ J. Am. Ceram. Soc., 48 [2] 16
2
3
2
3
2
3
(1965).
8
2 3 2
J. B. MacChesney and H. A. Sauer, ‘‘The System La O –TiO ; Phase Equi-
of PbO indicates that extra PbO is still available. ZrO
La Zr in amounts of more than 2% and 5%, respectively,
may indicate overcalcination.
2
and
libria and Electrical Properties,’’ J. Am. Ceram. Soc., 45 [9] 419 (1962).
F. H. Brown Jr. and P. Duwez, ‘‘The Systems Zirconia–Lanthania and
Zircomia–Neodymia,’’ J. Am. Ceram. Soc., 38 [3] 95 (1955).
O
2 7
9
2
1
0
Sintering of PLZT needs an effective PbO-protective atmo-
sphere. This gives a body with an intergranular fracture.
K. H. Ha
¨
rdtl and H. Rau, ‘‘PbO Vapor Pressure in the Pb(Ti1ÀxZr
x 3
)O Sys-
tem,’’ Solid State Commun., 7 [1] 41–5 (1969).
F. Xia and X. Yao, ‘‘The Role of PbO Content on the Dielectric and
11
2 2 7
The presence of La Zr O in the calcined powder can prevent
Piezoelectric Properties of PZN-Based Ceramics,’’ J. Mater. Sci., 36, 247–23 (2001).
B. Xu, L. E. Cross, and D. Ravichandran, ‘‘Synthesis of Lead Zirconate
12
the formation of porosity.
An ineffective PbO-protecting atmosphere results in a large
weight loss and results in an intragranular fracture.
Titanate Stannate Antiferroelectric Thick Films by Sol–Gel Processing,’’ J. Am.
Ceram. Soc., 82 [2] 306–12 (1999).
13
A. I. Kingon and J. B. Clark, ‘‘Sintering of PZT Ceramics: I, Atmosphere
Control,’’ J. Am. Ceram. Soc., 66 [4] 253–6 (1983).
14
A. I. Kingon and J. B. Clark, ‘‘Sintering of PZT Ceramics: II, Effect of
PbO Content on Densification Kinetics,’’ J. Am. Ceram. Soc., 66 [4] 256–60 (1983).
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15
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1
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‘
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2
17
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¨
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Pb,La)(TiZr)O
3
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3
18
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4
19
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1
974.
&