J. K. Juneja

In this paper, we are reporting structural, dielectric, ferroelectric and magnetic properties of polycrystalline composites (ferrite and ferroelectric) of PZT (PbZr_0.55Ti_0.45O₃) + CNFO (Co_0.8Ni_0.2Fe₂O₄). The sample with composition x CNFO + (1-x) PZT (x = 0.00, 0.05, 0.10, 0.15 and 1.00) were prepared using the solid state double sintering method. Here the ratio x: (1-x) of two components is by weight. X-ray diffraction (XRD) studies show that lattice constant and tetragonality decreases with increasing ferrite content. Dielectric constant was found to decrease with increase in amount of CNFO. The value of tangent loss (tanδ) was reasonably low (< 0.04) for all the samples. Ferroelectric and ferrimagnetic behavior was confirmed by observing P-E and M-H hysteresis loop, respectively. The room temperature magnetoelectric coupling coefficient (α = dE/dH) was measured as a function of applied DC magnetic field. The value of α was observed to be maximum (855 μV/(cm.Oe)) at DC magnetic field of 1.7 kOe for sample with 5% CNFO. Value of piezoelectric coefficient ‘d₃₃’ decreases from 133 to 60 pC/N.

A series of polycrystalline ceramics with compositional formula Ba_0.80−xSm_x Pb_0.20Ti_0.90Zr_0.10O₃, (0 ≤ x ≤ 0.01) was synthesized by solid state route. The effect of Sm substitution on ferroelectric and piezoelectric properties was studied. Ferroelectric properties were also studied as a function of temperature. Average grain size, determined from SEM micrographs, was found to decrease with increase in Sm content. Ferroelectric and piezoelectric properties were found to depend on microstructure. Coercive field ‘E_c’ and piezoelectric charge coefficient ‘d₃₃’ decreases with increase in Sm content. This indicates that Sm³⁺ is showing the softening behavior. The effect of grain size on ferroelectric and piezoelectric properties is discussed and presented in this paper.

In the present work, we are reporting the effect of Mn doping on the structural, dielectric and ferroelectric properties of Ba_0.80Pb_0.20Ti_0.90Zr_0.10O₃. Samples were prepared by solid state reaction route. X-ray diffraction analysis confirmed the compositions to be single phase. Dielectric properties were studied as a function of temperature and phase transition temperature (T_c) was determined. Ferroelectric behaviour was studied in detail as a function of temperature. Mn doping was found to improve temperature stability of the material.

Ceramics with compositional formula Ba_0.80Pb_0.20Ti_1-xZr_xO₃; x = 0.00, 0.02, 0.04, 0.06, 0.08 and 0.10 were synthesized by conventional solid state reaction method. The single phase with perovskite structure was confirmed by X-ray diffraction analysis for all the samples. The tetragonality was found to decrease with increasing zirconium content. The room temperature dielectric properties for all the samples were investigated in the frequency range 20 Hz to 1 MHz. It is observed that the increasing of zirconium content results in an increase in dielectric constant. The dielectric constant was found to decrease with increase in frequency.

Due to its important applications, there has been a great deal of interest in the fabrication as well as in the electrical and ferroelectric properties of barium titanate (BT)-based ceramics. The dielectric and ferroelectric properties of BT depends on the fabrication techniques and compositional modifications. In conventional solid state reaction technique, the main problem in fabrication of ceramics includes contamination from the tearing and wearing of balls and walls of the milling container, time and power consumption. Various attempts has been made in reducing the time and power consumption. Ultrasonic mixing of raw materials to prepare desired material is a method to reduce contamination and time & power consumption. X-ray diffraction confirms the existence of single phase. Comparative study of the dielectric properties shows the better stability of dielectric constant with frequency and temperature in case of barium titanate prepared using ultrasonically mixing.