LEAD ZIRCONATE TITANATE (PZT) 95/5
DOPING WITH NIOBIUM.
By
Anuja A. Hadke (141811002)
Guide
Prof. Appasaheb P .Pacharne
Department of Metallurgy and Material Science,
College of Engineering Pune 411005
Introduction to PZT.
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Lead zirconate titanate (PZT) is the most common piezoelectric
ceramic and exhibits excellent electro mechanical properties.
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Lead zirconate titanate (PZT) is a solid solution of PbTiO3 and
PbZrO3 with chemical formula Pb(Zrx Ti1- x)O3.
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PZT crystallizes in perovskite configuration.
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Various applications have been devised using their electro mechanical
transducer ability, including communication circuit components,
ultrasonic transducers, sensors, and actuators.
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PZT ceramics are almost always used with a dopant, a modifier to
improve and optimize their basic properties for specific applications.
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PZT thin films have been extensively studied
owing to their excellent dielectric, ferroelectric and
piezoelectric properties, which has made various
applications such as random access memory,
ferroelectric capacitors and micro-electromechanical systems (MEMS) possible in recent
years
Phase diagram of PZT
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PZT is a solid solution of two materials
(i) a ferroelectric lead titanate (PbTiO3), and
(ii) an anti-ferroelectric lead zirconate (PbZrO3).
PZT 95/5 (Zr:Ti ratio of 95:5)
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A ceramic solid Solution of PbZr0.95 Ti0.05 O3 :1%wt
Nb2O5 was obtained by classical sintering of
analytically pure PbO, Zr02, Ti02 and Nb2O5 oxides
in the adequate proportions
In this particular material, the ferroelectric /ant
ferroelectric (FE/APE) boundary is quite close to the
room temperature/pressure state
Characterization of PZT 95/5.
This material contains four to five major elements along with dopants
and impurities.
 PZT 95/5 materials exhibit spontaneous polarization, meaning that they
possess an electric dipole moment in the absence of an electric field.
 Material properties include1 high dielectric constant
2 high coupling
3 high charge sensitivity
4 high density
5 high Curie point
6 fine grain structure
7 clean and noise free frequency response
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Applications
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PZT is used to make ultrasound transducers both for loudspeakers and
microphones and other sensors and actuators, as well as high-value ceramic
capacitors and FRAM chips. PZT is also used in the manufacture of ceramic
resonators for reference timing in electronic circuitry.
Soft PZT is interesting when high coupling and charge sensitivity is important
such as ultrasonic non destructive testing and the evaluation of flow
measurements and object monitoring actuators for micro and nano positioning,
vibration detectors and electroacoustic applications as sound transducers and
microphones.
The first mass production of PZT thin films started in 1980’s thanks to the
computer data storage market. PZT replaced the dielectric layer of D8RAMs,
which enabled nonvolatility, that is it retains data in memory without power
supply.
The application of PZT thin films that followed was Integrated Passive Devices
(IPDs).
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The ferroelectric and piezoelectric properties of
perovskite-type titanates are employed in
many technological devices such as positive
temperature coefficient (PTC) resistors and
multilayer capacitors , generators, motors, ultrasonic
transductors, actuators, capacitors, or non-volatile
memories
Dopants used for PZT
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Basically, three types of additives were generally employed in the
compositional modification of PZTs. These include
(i) Isovalent dopants a) Similar valence and ionic radii of the replaced ions.
b) Lower the Curie point, enhance the permittivity, lower the loss
factor, and enhance the aging rate.
(ii) Donor dopants –
a) Higher valence cations such as La3C, Nd3C etc.
b) Acceptor” dopants are of lower valence cations.
c) Facilitates easy domain wall motion during poling resulting in
“soft” PZT.
(iii) Acceptor dopants –
a) Induce oxygen vacancy making the domain wall motion difficult,
thereby, these are known as “hard” PZTs.
Niobium
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Niobium is a lustrous grey, ductile, paramagnetic metal in group
5 of the periodic table , with an electron configuration in the
outermost shells typical for group 5
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Although it is thought to have a body-centered cubic crystal
structure from absolute zero to its melting point, high-resolution.
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Niobium becomes a superconductor at cryogenic temperatures.
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Niobium is slightly less electropositive and more compact than its
predecessor in the periodic table
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It has a lower density than other refractory metals
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The impact of small Niobium Addition to processing,
microstructure and electrical properties of Zr-rich
Lead Zirconium Titanate PZT 95/5
The Influence of Niobium Content on dielectric
responses and The characteristics of Ferroelectric
behaviour ,as well as the relative phase stability
and the hydrostatic pressure induced ferroelectric to
anti ferroelectric phase transformation are also
reported .
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Some Results indicates that increasing Niobium
concentration in the solid solution enhances the
densification, refines the microstructure ,decreases the
dielectric constant and spontaneous polarization and
stabilizes the ferroelectric phase.
Soft PZT ceramics result by doping with Nb5+ and
exhibit properties such as square hysteresis loops, low
coercive fields, high remnant polarization, high
dielectric constants, maximum coupling factors, higher
dielectric loss, high mechanical compliance, and reduced
aging
Manufacturing Processes
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PZTs were prepared by various processing routes
such as
1) Mixed oxide
2) Co-precipitation
3) Sol- gel
4) Spray pyrolysis
5) Hydrothermal synthesis
6) Molten salt synthesis etc.
Niobium addition to PZT 95/5
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Process1) PbO, Zr2O3, TiO2 and Nb2O5 were balled milled in double
distilled water for 2-3 hrs.
2) The filtered powder was then kept in an oven (for 24 hr) at
150ºC for drying.
3) Calcined at 900ºC for 6 hrs.
4) Then these powders were pressed into pellets of diameter
10 mm and thickness 1–2 mm using PVA as binder under a
pressure of 2 × 108 N/m2 using a uniaxial hydraulic press.
5) sintered at 1100ºC for 4 hrs.
6) The formation and quality of pellets were checked by X-ray
diffraction, Scanning Electron Microscope, RAMAN and Infrared
Spectroscopy ,ultrasonic (transducer )measurements,
Niobium addition to PZT 95/5
Results of Grain Size Measurement:
The average grain size was determined from
electron scanning microscope images to be of the order
of 10 µm; randomly distributed pure ZrO2 domains
have also been observed
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The pole figures indicated that the samples under study
exhibited a microstructure consisting of randomly
oriented, equiaxed grains.
X-rays diffraction spectra of Nb doped PZr95/5 ceramics at
room temperature
 showed all the lines of PZT 95/5 with no Nb doping")
 On the basis of these data. we conclude that both
antiferroelectric orthorhombic and ferroelectric
rhombohedral phases coexist in one ceramic grain at
room temperature, presumably due to local fluctuations of
composition, spontaneous polarization, temperature and
mechanical stress when cooling the samples during
preparation
 This coexistence was identified with diffraction contrast
transmission
electron microscope imaging.
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It is also reported that for Ti contents higher than x0.03 in PbZr1-x TixO3the temperature range of ant
ferroelectric orthorhombic and ferroelectric
rhombohedral phases coexistence broadens
rapidly; they observed a relative decrease in the Xrays diffracted intensities assumed to be a measure
of the change of the relative contents of the two
phases
TEM IMAGE
RAMAN AND INFRARED SPECIROSCOPY
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The Raman scattering experiments were carried out
on a Spex double monochromator with an Argon
ion laser and a photon counting. controller and data
acquisition system. The spectra were obtained in the
Stokes region of the 5145 A laser line The low
temperature spectra were recorded with samples
cooled by an Air Product displex cryostat.
Spectra recorded at 10K on PZT 95/5 %wt
Nb2O5 display peaks of various
 intensities, with a better resolution than at room
temperature. The temperature
 dependence between 10E and room temperature
of Raman back scattered spectra does
 not exhibit any important modification of the line
positions and widths, apart from the usual
thermal effect (figure 2).
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We thus conclude the absence of phase transitions below room
temperature. On
the contrary, when heating above the room temperature, two
diffuse phase transitions
toward phases of higher symmetry occur(5J6). manifested by low
frequency Raman
lines hehaving as soft modes. The higher frequency lines are still
present. but
broadened under heating up to Tferrepara = 235C the Curie
temperature of the first
phase transition being TC = 180C. Superimposed spectra of
PZT95/S:IXwtNb& at room
temperature, obtained under non polarized light. as well as in the
HH and HV
polarization configurations. do not show any noticeable selection of modes. in
accord
with the isotropy of the samples, established by our texture measurements.
XRD patterns
XRD patterns of (a) undoped, (b) 1% Nb-doped, (c) 2% Nb-doped, (d) 3% Nb-doped, (e)
4% Nb-doped and (f) 5% Nb-doped
PZT thin films.
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(1) The orientation and microstructures
shows the XRD patterns of undoped and Nb doped
PZT thin films with different Nb doping concentration.
It can be noted that all films are completely
crystallized in polycrystalline perovskite and scarcely
any pyrochlore phase is observed. The crystal structure
of the PNZT thin films is closely related with the
doping concentration. When the concentration of Nb
dopant is below 5%, the PNZT films exhibit combined
orientations of the (100), (110) and (111) directions,
in which the (100) orientation is the dominant growth
SEM IMAGES
The surface SEM images of (a) undoped, (b) 4% Nb-doped PZT thin films.
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The surface and cross-section SEM images of PNZTthin
films with different Nb doping concentration are shown
When the doping concentration is
less than 5%, all the films reveal no cracks, distinct grain
boundaries and dense columnar microstructure
As the Nb doping concentration increases to 5%, the PNZT
film is presented with an unclear grain boundary, which
may be due to the non-dense perovskite structure of the
film.
In addition, the grain size of 4% Nb-doped PZT film is
found to be larger than that of the other films.
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in Fig. 4(f)). In addition, the grain size of 4% Nb-doped
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PZT film is found to be larger than that of the other films.
The cross-section SEM images of (a) undoped, (b) 1% Nb-doped, (c) 2% Nb-doped,
(d) 3% Nb-doped, (e) 4% Nb-doped and (f)
5% Nb-doped PZT thin films
DIEELECTRIC CONSTANT
The dielectric constant of PNZT thin films with different Nb
doping concentration as a function of frequency.
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shows the dielectric constant of PNZT thin films
with different Nb doping concentration as a function of
frequency ranging from 0.1 to 100 kHz at room
temperature.
It can be observed that the dielectric constant of
all the films decreases as the frequency increases. At lower
frequencies, the higher value of the dielectric constant
is due to simultaneous presence of all types of polarizations
like electronic, ionic and space charges polarization.
But at higher frequencies, some polarizations become
ineffective and only electronic polarization works.
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The prepared PZT and PZTN powders calcined at 850
°C were used for preparation of ceramic discs or
pallets . The powders were mixed with 5 wt.% of a
water solution containing 10% polyvinyl alcohol (PVA)
and pressed into discs with 10 mm in diameter and 1–2
mm in thick-ness in stainless steel dies under uniaxial
pressure of 150 MPa.
The pressed discs were placed in a covered alumina
crucible where atmosphere was controlled by the
addition of the pure PZT (52/48) + 10% ZrO2 powders in the crucible without contact with the samples
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The discs were sintered at 1100, 1150 and 1200
°C for 1–6 h, with 4 h holding at 550 °C to burnout the binder. The initial heating rate was set to be
5 °C/min up to the burn-out temperature and then
a heating rate of 10 °C/min was used up to the
final sintering temperature.
Properties we are going to observe
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XRD ANALYSIS
DIALATOMETRIC RESULTS
GRAIN SIZE MEASURMENT
SEM ANALYSIS
TEM ANALYSIS
REFERENCES
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www.resarchgate.com
www.sciencedirect.com
Article:The Effect of Acceptor and Donor Doping
on Oxygen Vacancy Concentrations in Lead
Zirconate Titanate (PZT)
Structural and spectroscopic studies of niobium
doped PZT 95/5 ceramics-From Ferroelectrics
research paper
Role of Niobium in development of PZTonlinelibrary.willey.com and researchgate.com
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Introduction – Research papers from
researchgate,sciencedirect
Experimental Procedure- – Research papers from
researchgate,sciencedirect
Chracterization-– Research papers from
researchgate,sciencedirect
Die Electric Measurement -– Research papers from
researchgate,sciencedirect
Results and discussion – Research papers from
researchgate,sciencedirect
Characterization of PZT and PZTN powder – Research
papers from researchgate,sciencedirect
Questions?
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