Characterization of (0.4)Pb
2
(In,Nb)O
6
:(0.6)Pb(Mg
1/3
Nb
2/3
)O
3
relaxor ceramics
K.Z. Baba-kishi, C.W. Tai, J. Wang, C.L. Choy, and H.L.W. Chan
Department of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic
University, Hung Hom, Kowloon, Hong Kong
A.S. Bhalla
The Pennsylvania State University, Materials Research Laboratory,
University Park, Pennsylvania 16802
(Received 21 June 2001; accepted 22 November 2001)
The results of the development and characterization of a new relaxor ceramic with
nominal composition (x)Pb
2
(In,Nb)O
6
(1 - x)Pb(Mg
1/3
Nb
2/3
)O
3
solid solution
with x 0.4 are reported. The structural characteristics, including the long-range and
short-range order, forbidden reflections, and the existence of mixed ordering, were
studied by transmission electron microscopy. The most prominent microstructural
feature of this compound, which has composition variations in the micro- and
nano-regions, was investigated. The presence of the pyrochlore phase and the complex
arrangement of inclusions that originate from processing are illustrated. The electrical
characteristics of the compound including pyroelectric, piezoelectric, electrostrictive
and hysteresis properties are reported. Notable properties of the compound include a
reduced hysteresis loop and nonlinear behavior at high field.
I. INTRODUCTION
The outstanding properties of piezoelectric crystals
and ceramics can be related to the influence of morpho-
tropic boundary phases and the development of domains.
Morphotropic boundary phase is important in terms of
composition, structure, and the division between at least
two different crystal structures.
1
In Pb(Zr
x
Ti
1-x
)O
3
(PZT), a morphotropic phase boundary separates the fer-
roelectric phase into two regions with distinct crystal
structures: one is a tetragonal phase with Ti-rich compo-
sition, and the other is the rhombohedral phase with Zr-rich
composition. In the region Zr/ Ti 53/47, the material has
good piezoelectric properties, whereas in the solid solution
regions 100/0 and 94/6, it is antiferroelectric with an or-
thorhombic structure, which lacks any piezoelectric prop-
erty.
2
There is also an abrupt change of the lattice
parameters close to the composition at the morphotropic
phase boundary. Another material of significant complexity
and importance is (1 - x)Pb(Mg
1/3
Nb
2/3
)O
3
:xPbTiO
3
, in
which the morphotropic phase boundary is at x 0.35.
This material has an overall cubic symmetry according to
x-ray and neutron diffraction studies but shows a complex
domain configuration, which indicates the presence of a
rhombohedral phase or an intermixing of both the te-
tragonal and rhombohedral phases.
3–6
The crystallographic parameter often seen as a de-
termining factor in the behavior of broad relaxation
peak is structural ordering. A large number of Pb-based
ferroelectric compounds undergo some degree of struc-
tural ordering, which has been extensively studied.
7–9
Some examples are Pb
2
(Sc,Ta)O
6
, Pb
2
(Mg,W)O
6
,
and Pb(Mg
1/3
Nb
2/3
)O
3
, which possess complex crystal
structures.
Studies on the fundamental crystal structures of the
ferroelectric and pyroelectric Pb
2
ScTaO
6
have been car-
ried out.
10–13
The structure of the relaxor Pb
2
ScTaO
6
has
been refined from high-resolution neutron time-of-flight
powder diffraction data at both 400 and 4.2 K.
11
In
Pb
2
ScTaO
6
at 4.2 K, in the ferroelectric state, the struc-
ture is rhombohedral with a space group R3. According
to the refinements, the structure of Pb
2
ScTaO
6
in the
ferroelectric state differs from the paraelectric state by
cooperative ion shifts. The crystal structure of another
ferroelectric oxide, Pb
2
ScNbO
6
, which is related to
Pb
2
ScTaO
6
, has also been studied in a similar manner
to that of Pb
2
ScNbO
6
.
12
The coordination polyhedra con-
tain stereo-active lone electron pairs on Pb
2+
. The Sc
3+
and Ta
5+
ions are shifted away from the centers of their
respective octahedra towards the octahedral faces. These
studies now enable a better understanding of the ways
ferroelectric phase transition takes place in both
Pb
2
ScTaO
6
and Pb
2
ScNbO
6
.
By mixing Pb
2
(In,Nb)O
6
(PIN) with relaxor
Pb(Mg
1/3
Nb
2/3
)O
3
(PMN), we maintain the relaxor be-
havior across the phase diagram when the two materials
are in the disordered states. The combination of PIN
and PMN produces morphotropic boundary phases with
J. Mater. Res., Vol. 17, No. 2, Feb 2002 © 2002 Materials Research Society 438