ABSTRACT In this work we have investigated the microstructure and properties of new compositions of

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COMPLEX RARE EARTH SUBSTITUTED LEAD TITANATE
PIEZOCERAMICS
E.Dimitriu, F. Craciun , R. Ramer , V.
Ciupina, G. Prodan  Interdisciplinary Research
Institute for Micro and Nanostructure, University
Ovidius, Constanta, Romania Istituto di
Acustica O.M. Corbino, Area di Ricerca Tor
Vergata, Via del Fosso del Cavaliere 100,
I-00133, Rome, Italy School of Electrical
Engineering, University of South Wales, Sydney
2052, Australia
ABSTRACT In this work we have investigated the
microstructure and properties of new compositions
of Gd, Nd and Pr - added Pb(Ti,Mn)O3 ceramics,
containing a few percent of Bi, to partially
substitute lead. The samples have been prepared
by solid-state reaction, using high purity
oxides, within the sintering range 1100-1220oC.
Structural and morphological investigations were
performed on poled samples. The use of X-ray
diffraction together with microstructural
examination by transmission electron microscopy
has shown evidence for the formation of
tetragonal perovskite phase. The domain structure
and the lattice imperfection of the PT-type
samples have been investigated by a high
resolution transmission electron microscope
(HRTEM). Samples with diameter 10 mm and
thickness 1 mm have been employed for electrical
characterization. Material coefficients have been
investigated as a function of temperature.
Dielectric permittivity and resistivity were
measured with a four-wire probe in a wide
temperature and frequency range.
Pb0.88Nd0.08Ti0.98Mn0.02O3 0.01 wt Bi2O3
(PT-N)
Pb0.88Gd0.08Ti0.98Mn0.02O3 0.01 wt Bi2O3
(PT-G)
PIEZOELECTRIC PROPERTIES
ELECTRICAL PROPERTIES
PT-P
PT-N
PT-G
Frequency dependence of conductivity in PT- type
ceramics at room temperature
Nanodomains in a region of inhomogeneity
PT-P
PT-G
PT-N
PT-P
PT-P
SAED image of sample with marked line indexed in
the left insert. Crystal structure P4 mm a
0.389 nm c 0.415 nm
HRTEM micrograph with lattice planes and
interplanar distances
Temperature dependence of conductivity in PT-type
ceramics at various
The conductivity was calculated with the formula
? ?0 ? tan ? 2?f, where f is the driving
signal frequency. The dielectric constant (real
part) ?, dielectric loss (tan?) and conductivity
? versus T, were determined from measurements of
capacitance and tan ? of ferroelectric capacitor
at different frequencies of the driving signal
(0.5, 1, 10, 100, 200 kHz). The temperature was
increased with 1.5 0C/min from 25 0C (room
temperature) to 150 0C. There are not any
sensible difference between the results of
measurements made on heating or cooling the
samples in the explored temperature range.
PT-N
The dependence of the piezoelectric properties
on the temperature
SAED pattern of lattice planes
HRTEM images a single crystal oriented along
001 and another rigth side arrow that exibit
fringes for (101) planes.
Pb0.88Pr0.08Ti0.98Mn0.02O3 0.01 wt Bi2O3
(PT-P)
Physical properties for materials sintered at
1180oC/2h
SAED image of sample with marked line indexed in
the left insert
HRTEM image representing inhomogeneity in
structure
SAED image of a monocrystal

• CONCLUSIONS
• PT-type materials with tetragonal structure were
  prepared. The lattice anisotropy for the PT-Gd is
  high c/ a 1.066 . Fine width domains are
  developed in the near grain boundary of poled
  samples along with regions of in homogeneity. The
  domains are not aligned in the same direction,
  possible due to the poling conditions.
• The multiple substitutions in A and B positions
  lead to a change in the structural ordering. A
  redox system is formed in the solid solution, and
  the ions with multiple oxidation states may
  co-exist (Ti41-x Ti3x), (Pr31-x Pr4x),
  (Mn41-x Mn5x).
• The conductivity of the materials increases
  almost linearly with the increasing of the
  temperature. A high dependence of the
  conductivity with the frequency is observed the
  values of the conductivity increase with two
  order of magnitude in the frequency range from
  0.5 kHz to 200 kHz.
• The dependence of the electromechanical
  anisotropy on the temperature for the PT-P
  material is linear this material could be used
  for SAW devices.
• A discontinuity in the slope of the conductivity
  and electromechanical anisotropy function of the
  temperature, at 40oC, is observed for the
  material PT-G. At the same temperature the slope
  of the dependence kT/k31 is modified, showing
  that at this temperature a change in the ceramic
  structure takes place.

Filtered HRTEM image representing interference
fringes from (001) planes in a single crystal
Acknowledgements IEEE-UFFC - for financial
support POLECER network (membership agreement
19/2003) Romanian MECT (Grant 19/2003)
2004 IEEE International Ultrasonics,
Ferroelectrics and Frequency Control 50th
Anniversary Conference