Ferroelectrics

Topics: Piezoelectricity, Ferroelectricity, Lead zirconate titanate Pages: 5 (1375 words) Published: August 23, 2013
The Effect of Excessive Sm3+ doping on the Ferroelectric properties of Lead Zirconate Titanate Ceramics

T. Anil Babu*, K.V. Ramesh+, V.Raghavendra Reddy@ and D.L. Sastry*

* Physics Department, Andhra University, Visakhapatnam – 530 003 (AP) + Department of Engineering Physics, GITAM University, Visakhapatnam – 530 045(AP) @ UGC-DAE Consortium for Scientific Research, University Campus, Indore-(MP) Email: dl_sastry@yahoo.com

Abstract. Polycrystalline samples of Sm modified Pb Zrx Ti(1-x) O3 [PZT] ceramics ( where x = 0.6,0.7,0.8,0.9) have been prepared by a high energy ball milling technique, which was followed by calcination at 9500 C and sintering at 11500 C. As Sm3+ concentration is increased more than 0.1 mole% considerable pyrochlore phase has been formed. This phase has been identified as Sm2Ti2O7 from its X-ray diffraction peaks. X-ray diffraction (XRD) and Scanning electron mcroscopy (SEM) studies have been carried out to determine the structural phase and morphological modifications that occur with the change in Zr/Ti ratio. The ferroelectric phase transition temperature (Tc) decreases and increases where as the dielectric constant (ε’) increases and decreases. The saturation polarization Ps (μc/cm2), remnant polarization Pr (μc/cm2) and coercive field Ec (kv/cm) values of the perovskite in the presence of the pyrochlore are presented.

Key Words: Ferroelectric Properties, Dielectric Constant, Sm3+ doping, Lead Zirconium Titanate, Pyrochlore PACS: 77.80.-e, 77.80.B-, 77.22.-d; 77.80dj; 77.84Cg.

Introduction

LEAD ZIRCONATE TITANATE IS A PEROVSKITE MATERIAL OF ABO3 STRUCTURE WITH SEVERAL APPLICATIONS SUCH AS ACTUATORS, TRANSDUCERS, PYROELECTRIC DETECTORS, ELECTROOPTIC MODULATORS, RANDOM ACCESS MEMORIES ETC. IT IS A SOLID SOLUTION OF FERROELECTRIC PBTIO3 AND ANTIFERROELECTRIC PBZRO3 WITH A MORPHOTROPIC PHASE BOUNDARY EXISTING AT ZR/TI RATIO OF 48/52. THE MATERIALS HAVE VERY INTERESTING PHYSICAL PROPERTIES AT THE COMPOSITION AROUND MORPHOTROPIC PHASE BOUNDARY (MPB). HOWEVER ABOVE AND BELOW MPB ALSO THE MATERIALS HAVE INTERESTING PHYSICAL PROPERTIES USEFUL FOR DEVICE APPLICATIONS. THE PHYSICAL PROPERTIES OF PZT CERAMIC COMPOUNDS ARE GREATLY INFLUENCED BY THE SUBSTITUTION OF DIVALENT OR TRIVALENT IONS IN THE PLACE OF PB2+. THE METHOD OF PREPARATION SUCH AS SOLID STATE REACTION OR WET CHEMICAL METHODS OR MECHANOCHEMICAL SYNTHESIS ARE ALSO SUPPOSED TO INFLUENCE THE PHYSICAL PROPERTIES AND HENCE THE PARAMETERS THAT ARE USEFUL FOR DEVICE FABRICATIONS. IN THE PRESENT WORK WE HAVE CHOSEN PZT WITH ZR/TI IN THE RATIO OF 50/50 WHICH IS ON THE TETRAGONAL SIDE OF THE MPB WHICH IS A FERROELECTRIC PHASE AT THE ROOM TEMPERATURE. THE METHOD OF PREPARATION CHOSEN IS HIGH ENERGY BALL MILLING COMBINED WITH CALCINATION AT 9500C. IN THIS MATERIAL SM3+ RARE EARTH ION IS SUBSTITUTED IN THE PLACE OF PB TO GIVE PB1-X SMX (ZR0.5TI0.5) O3 (PSZT) WHERE X IS VARIED FROM 0.1 TO 0.4. IN THE PRESENT COMMUNICATION RESULTS OBTAINED FOR PSZT WHERE SM3+ CONCENTRATION FOR X= 0.1 AND 0.4 ARE PRESENTED.

EXPERIMENTAL

The samarium substituted (PSZT) materials were prepared by taking high purity PbO, ZrO2, TiO2 and Sm2O3 in the required stoichiometric ratio and milled at room temperature using a INSMART systems planetary ball mill for nearly 24hours adding methanol to obtain a homogeneous mixture of the starting materials. Tungsten carbide balls were employed in the milling process and milling speeds of 300rpm were used. Milling was stopped every one hour for 10minutes to allow the contents to cool. The tungsten carbide balls were of 8mm&10mm diameter and the ball to powder ratio employed was 10:1. The as prepared samples were calcined at 950oC for 3hrs so as to completely react any remaining unreacted ingredients. The calcined powders were thoroughly ground adding a small amount of PVA and made into pellets of 10mm diameter under a pressure of 3ton/mt2 using hydraulic press. The pellets were...

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