International Journal of Scientific & Engineering Research, Volume 5, Issue 4, April-2014 404

ISSN 2229-5518

Structural and Dielectric Properties of PZT Ceramics

Prepared by Solid-state Reaction Route

Mridula Kumari, Arun Singh, Jagdhar Mandal

Abstract− Polycrystalline Pb (Zr1-x Ti x )O 3 with x = 0.50 abbreviated as PZT has been prepared by high energy solid-state reaction technique. Analysis of XRD patterns of this composition suggests the formation of PZT phase with tetragonal structure. SEM studies were used for microstructural characterization. The dielectric properties of PZT ceramics have been characterized. The measurements have been made in frequency ranging from 100

Hz to 1 MHz and between room temperature (RT) and 550ºC for low and high frequencies. At RT, the value of dielectric constant (ε r ) is 515.492 at 1

KHz whereas the loss tangent is 0.005. From ε r (T) measurements, the Curie temperature of our sample has been determined at 380ºC. The increase of ε r

observed at high temperatures and low frequencies in the paraelectric state are explained, this abnormal behavior is due to the migration of oxygen ions

towards the electrodes.

Keywords− Dielectric properties, PZT, Phase transition, SEM, Solid-state reaction technique, XRD etc.



1 INTRODUCTION

ead zirconate titanate Pb (Zr1-xTix )O 3 or PZT, is one of the best known ferroelectric materials due to its remarkable ferroelectric and piezoelectric properties in polycrystalline form [1-3]. It is most widely used piezoelectric ceramic materials in devices like actuators, ultrasonic transducers, sensors, resonators, ferroelectric memory,
optoelectronic, piezoelectric transformers [4-6].
Lead zirconate titanate, Pb(Zr1-xTix )O3 or PZT, is solid
solution of two simple perovskite, lead titanate (PbTiO3 ) and lead zirconate (PbZrO3 ) with broad range of curie temperature. These compounds crystallize in ABO3 type structure, where the A and B-sites are occupied by Pb2+ and (Zr4+, Ti4+) ions respectively. At room temperature PZT, presents two ferroelectric phases, a tetragonal phase in the titanium rich and a rhombohedral phase one in the zirconium rich side [7-8]. A wide range of compositions of PZT ceramics have been investigated with an emphasis on dielectric, piezoelectric and pyroelectric properties. Near the morphotropic phase boundary (MPB), PZT has maximum value of the dielectric and the electromechanical coupling coefficients. Lead zirconate titanate (PZT) material continues

_____________________________________

1. Author

Mridula Kumari, University Department of Physics, TMBU, Bhagalpur-

812007, Bihar, India.

Arun Singh, Jamia Millia Islamia, New Delhi-25.

to be well-studied system because of its technologically
important applications.
The main objective of this work is to prepare and characterize the perovskite type compounds capable enough to continue in pyroelectric and electronic applications.

2 EXPERIMENTAL PROCEDURE

PZT ceramics were prepared by the conventional solid state reaction. The raw materials, PbO, ZrO2 , and TiO2 were weighted according to the stiochiometric formula Pb (Zr1 – xTix )O 3 with x = 0.50. An excess of 5 wt% PbO is added to starting materials to compensate for the evaporation of lead during sintering at high temperature. The raw materials were mixed first in air medium then in ethanol medium with the help of agate mortar and pestle. The mixed material was calcined in alumina crucible at temperature 875ºC for 2hr at heating and cooling rate 5ºC /minute. The calcined powders were further mixed and 5 wt% poly vinyl alcohol (PVA) were added to the mixture as a binding agent. After this powders was converted into cylindrical pellets in steel die punch by applying pressure with the help of hydraulic press. Pellets were sintered at 1200ºC for 2hr with the heating and cooling rate 5ºC /minute. During sintering, PbZrO3 was used as lead source in the crucible to minimize volatilization of lead.
The XRD spectra were observed on sintered pellets with
an X-ray diffractometer (Brucker D8) at room temperature, using CuKα radiation over a wide range of Bragg angles (20º ≤ θ ≤ 80º). The morphology, exact size, shape and distribution of the lead zirconate titanate (PZT) particles were determined by scanning electron microscope (SEM, Carl Evo
40). For dielectric measurement, pellets were electrode with platinum by RF sputtering. Dielectric studies were done by measuring capacitance of the sample with Agilent 4284A precision LCR meter as a function of frequency and temperature.

International Journal of Scientific & Engineering Research, Volume 5, Issue 4, April-2014 405

ISSN 2229-5518

3 RESULTS AND DISCUSSION

3.1 STRUCTURAL AND MICROSTRUCTURAL STUDY

Fig.1 shows the XRD patterns of PZT ceramic with stiochiometric composition of Pb (Zr1-xTi x)O3 (x = 0), collected at room temperature. According to literature, the XRD pattern of PZT ceramic at room temperature corresponds to a single phase tetragonal perovskite structure,
with its a-axis value is 4.027 and c/a ratio is 1.023, which is in
observed in the sample. The value of average grain size is consistent with the value of nearly equal to 1.55µm reported in the literature [11].

3.2 DIELECTRIC PROPERTIES

Fig.3 shows the variation of dielectric constant (εr ) with frequency at room temperature. It is observed from dielectric constant (εr ) vs frequency curve (fig.3) that the dielectric constant demonstrate sharp decline up to 95KHz thereafter it

This image cannot currently be displayed.

Pb(Zr

Ti )O

1-x x 3

x = 0.50

20 30 40 50 60 70 80

2θ (degrees)

Fig.1 Room temperature XRD pattern of PZT ceramic

consistent with the reported value in the literature [9-10]. The sharpness of the diffraction peaks in the XRD pattern suggests better homogeneity and crystallinity of the PZT ceramic.
Fig.2 Shows the scanning electron micrograph of PZT

ceramic with the composition Pb(Zr1-xTi x)O3 with x = 0.50. From the nature of micrograph that the grains are nearly spherical in shape, low porosity and no grain growth was
shows a gradually decline in its value up to higher frequency. The value of dielectric constant (εr ) at 1 KHz is 515.492 and value of dielectric loss (tanδ) is found to be 0.005 at same frequency.

Dielectric measurements have been carried out from
RT to 550ºC in the frequency 500Hz to 1MHz. This enables the examination of the transition from tetragonal ferroelectric state to cubic paraelectric state. Fig.4 shows the curves for PZT ceramic at various frequencies between 500Hz and
1MHz. A maximum is observed at TC = 380ºC. It is

International Journal of Scientific & Engineering Research, Volume 5, Issue 4, April-2014 406

ISSN 2229-5518

independent of frequency which is characteristics of classical ferroelectric. The anomalies in the dielectric constant (εr ) after its maximum values are observed at lower frequencies (500
Hz & 1 KHz). In the paraelectric region at frequencies lower
than 100 KHz the increase of dielectric constant (εr ) at higher temperatures are due to the migration of oxygen ions [12].
The maximum value of εr are 17042.223, 15131.287,
10639.699, 9961.424 and 9406.022 at frequencies 500 Hz, 1
KHz, 100 KHz, 500 KHz and 1MHz respectively.

4 CONCLUSIONS

Pb(Zr1-xTix )O3 (x = 0.50) ceramics have been successfully prepared by a solid-state reaction technique. The XRD pattern of the PZT ceramic confirmed their single phase perovskite with tetragonal structure. SEM studies reveals that the average grain size of the PZT ceramic is found to 1.55µm. At room temperature and frequency at 1 KHz, the dielectric study of the PZT ceramic gives a dielectric constant εr =
515.492 and a loss tangent tanδ = 0.005. Measurement at high temperatures permit to determine, from the maximum of εr (T), the Curie temperature TC = 380ºC of the ferroelectric- paraelectric phase transition of PZT ceramic.

ACKNOWLEDGEMENT

One of the authors, Mridula Kumari wishes to acknowledge the laboratory facilities provided by Professor Binay Gupta, Chairman, Nano Science Technology, Delhi University.

REFERENCES

[1] Y. Xu, Ferroelectric Materials and Their Applications

(North Holland, Amsterdam, 1991).
[2] G. Saghi-Szabo and R. E. Cohen, First-principles study of piezoelectricity in tetragonal PbTio3 and PbZr1/2 Ti1/2 O3 ; Phys. Rev. B, Vol. 59, No. 20.
[3] Z. Zhang, P. Wu, K. P. Ong, L. Lu and C. Shu; Electronic properties of A-site substituted lead zirconate titanate: Density functional calculations; Phys. Rev. B 76, 125102 (2007). [4] R. C. Buchanan, Ceramic Materials for Electronics, Marcel Dekker, New York, 1991.
[5] G. H. Haertling, Ferroelectric Ceramics : History and
Technology; J. Am. Ceram. Soc. 82 (1999) 797
[6] P. Muralt, J. Micromech. Microeng. 10, 136 (2000).
[7] M. R. Soares, A. M. R. Senos and P. Q. Mantas, Phase
coexistence region and dielectric properties of PZT ceramics;

J. Eur. Ceram. Soc. 20 (2000) 321-334.

[8] B. Noheda, J. A. Gonzalo, L. E. Cross, R. Guo, S. E. Park,
D. E. Cox and G. Shirane, Tetragonal- to-Monoclinic phase transition in a ferroelectric perovskite : The structure of PbZr0.52 Ti0.48 O3 ; Phys. Rev. B, Vol. 61, No. 13.
[9] R. Tipakontitikul and S. Ananta, A modified two-stage mixed oxide synthetic route to lead zirconate titanate powders; Mat. Lett. 58 (2004) 449-454.
[10] L. B. Kong, W. Zhu and O.K. Tan; Preparation and
characterization of PbZr0.52 Ti0.48 O3 ceramic from high energy ball milling powders, Mater. Lett. 42 (2000) 232-239.
[11] X. junmin, J. Wang and T. Weiseng; Synthesis of lead
zirconate titanate from an amorphous precursor by mechanical activation, J. Alloys and Compds. 308 (2000) 139-
149.
[12] D. Fasquelle and J. C. Carru, Electrical characterization of
PZT ceramics in large frequency and temperature range; J.

Eur. Ceram. Soc., 28 (2008) 2071-2074.