Sangeeta Singh

INFLUENCE OF SAMARIUM SUBSTITUTION ON DIELECTRIC PROPERTIES OF BARIUM TITANATE BASED CERAMICS

In this paper we report samarium substituted Ba0.80Pb0.20Ti0.90Zr0.10O3 (BPZT) ceramics. The material series with compositional formula Ba0.80-xSmxPb0.20Ti0.90Zr0.10O3 with x varying from 0 to 0.01 in the steps of 0.0025 was chosen for investigations. The material was synthesized by solid state reaction method. Reacted powders compacted in the form of circular discs were sintered at 1325°C. All the samples were subjected to X-ray analysis and found to be single phase. Dielectric behavior was studied as a function of frequency and temperature and Curie temperature (Tc) was determined. Tc was found to decrease with increasing x. The details are discussed and presented here.

Ferroelectric Properties of Microwave Processed PZT-NiZn Ferrite Composites

Being materials with a large number of interesting properties, ferroelectric-ferrite based composites have recently been developed. People are showing a great interest in these materials due to some unique properties like magnetoelectric effect in addition to the ferroelectric, dielectric and magnetic properties. After a review of literature it is found that the variation in different properties of PZT ceramics is found to depend on the amount of ferrite content. In this paper, we are reporting the variation in ferroelectric properties of PbZr0.65Ti0.35O3 (PZT) by varying Ni-Zn ferrite (NZF) content. The studied system having compositional formula (1-x) PZT–x NZF (0 ≤ x ≤ 0.025, in steps of 0.005), was prepared by solid state route using microwave sintering. Remanant polarization was found to be monotonically decreasing with increasing ferrite content as observed from the recorded P-E hysteresis loops for all the samples at 20 Hz. Microwave sintering results in significant improvements in properties as compared to conventionally sintered samples.

Structural, Dielectric and Ferroelectric Properties of Mn Doped Ba0.80Pb0.20Ti0.90Zr0.10O3 Ceramics

In the present work, we are reporting the effect of Mn doping on the structural, dielectric and ferroelectric properties of Ba0.80Pb0.20Ti0.90Zr0.10O3. 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 (Tc) was determined. Ferroelectric behaviour was studied in detail as a function of temperature. Mn doping was found to improve temperature stability of the material.

Structural, Dielectric, Ferroelectric and Ferromagnetic Properties of Ba0.9Sr0.1ZrxTi1-xO3+ 5% Ni0.8Zn0.2Fe2O4 Composite

The composites consisting of Mn doped Ni0.8Zn0.2Fe2O4 and Zr substituted Ba0.9Sr0.10TiO3 (BST) where Zr varies from 0.00 to 0.16 in steps of 0.04 were prepared by conventional solid state reaction route. The existence of both phases was confirmed by the XRD patterns and the lattice parameters for each composition were calculated. The dielectric parameter such as dielectric constant and dielectric loss were measured as a function of frequency and temperature. As we increase the Zr in ferroelectric phase, the dielectric loss of composite samples decreases up to 1% from 8%, and also Tmax decreases towards room temperature. Observation of ferroelectric and magnetic hysteresis loops for all samples confirms the electric and magnetic nature of the samples.

Dielectric and Ferroelectric Properties of BST and Ni-Zn Ferrite Composites

Ferroelectric—ferrite composites are very important materials as they show both electric and magnetic properties and are drawing attention of researchers over the last few years due to their immense contribution to the improvement of science and technology. Electrical and ferroelectric properties of such ceramic materials are strongly dependent on composition and ratio of two constituents. In the present paper we are reporting the dielectric and ferroelectric properties of (1-x)Ba0.90Sr0.10TiO3- xNi0.80Zn0.20Fe2O4, (0 ≤ x ≤ 0.02 steps of 0.01) (BST-NZF) mixed phase materials. Both the constituent materials were prepared separately by conventional solid state method and then finally mixed by weight to form the mixture. The dielectric properties were measured as a function of temperature at 100 Hz, 1 kHz, 10 kHz and 100 kHz frequencies. P-E hysteresis loops were recorded at 20 Hz for all the mixture samples. Remanent polarization was found to decrease with increase in ferrite content. Magnetization measurements show the samples to be in ferromagnetic state. Structural analysis was done by X-ray diffraction analysis.

Structural, Dielectric and Magnetoelectric Properties of x Co0.8Ni0.2 Fe2O4 + (1-x) PbZr0.55Ti0.45O3 Composites

In this paper, we are reporting structural, dielectric, ferroelectric and magnetic properties of polycrystalline composites (ferrite and ferroelectric) of PZT (PbZr0.55Ti0.45O3) + CNFO (Co0.8Ni0.2Fe2O4). 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.

Dielectric, ferroelectric and ferromagnetic properties of x Ni0.8Zn0.2Fe2O4-(1-x) Pb0.99La0.02Zr0.65Ti0.35O3 composites

For the present study, two phase ceramic (ferroelectric-ferrite) composites using La substituted lead zirconate titanate (PLZT) and Ni-Zn ferrite (NZF) with compositional formula x Ni0.8Zn0.2Fe2O4-(1-x) Pb0.99La0.02Zr0.65Ti0.35O3 (x = 0, 0.05, 0.10 and 0.15) were synthesized by conventional solid state reaction route. From X-ray analysis, it was confirmed that no chemical reaction took place between individual phases. Dielectric properties were studied as a function of temperature and frequency. Decrease in dielectric constant and increase in dielectric loss was observed with increasing ferrite content. Anomalous behavior in paraelectric region was observed for all the composite samples (x = 0.05, 0.10 and 0.15) at low frequencies. To study ferroelectric and ferromagnetic properties, P-E and M-H hysteresis loops were recorded respectively. Effect of electric field on magnetization was studied for all composite samples to confirm magnetoelectric coupling.

Structural, Electrical and Magnetic Properties of Microwave Processed Ni0.80Zn0.20Fe2O4

The material sample was prepared by conventional solid state method and sintered in conventional and microwave furnace at different sintering temperatures. Sintered samples were then subjected to XRD and SEM analysis. X-ray diffraction revealed the formation of single phase material. SEM of fractured cross sectional portion showed that finer grains were formed in case of microwave sintering. The dielectric properties and magnetic properties were recorded for both the samples and both properties were found to improve in microwave sintered samples. There is also a significant improvement in density and magnetic properties by microwave processing.

Ferroelectric, Magnetic and Magnetoelectric Properties of Ferroelectric Rich Ni0.8Zn0.2Fe2O4-PbZr0.65Ti0.35O3 ME Composites

Magnetostrictive-piezoelectric (magnetoelectric) composites using magnetostrictive nickel zinc ferrite (NZF) and piezoelectric lead zirconate titanate (PZT) having compositional formula yNi0.8Zn0.2Fe2O4-(1-y)PbZr0.65Ti0.35O3 (0 ≤ y ≤ 0.15 in the steps of 0.05) were synthesized by conventional solid state method. Room temperature P-E and M-H hysteresis loops were recorded to study ferroelectric and magnetic properties of composites respectively. Effect of electric poling on values of remanant magnetization (Mr) and saturation magnetization (Ms) was studied for all composite samples (y = 0.05, 0.10 and 0.15) to confirm magnetoelectric (ME) coupling. ME coefficient (dE/dH) was measured as a function of dc magnetic field for all composite samples.

Influence of Zr Substitution on Ferroelectric Properties of BST Ceramics

Zirconium substituted strontium modified barium titanate ceramics with compositional formula Ba0.9Sr0.1Ti1-xZrxTiO3 (0 ≤ x ≤ 0.16 in steps of 0.04) were prepared by the solid state reaction route. Effects of substitution of Zr4+ on the physical and ferroelectric properties were studied. Decrease in relative density with increase in Zr content was observed. Ceramic sample with 4 mol% Zr showed maximum remnant polarization (11.5 μC/cm2) and coercive field (3.2 kV/cm). Microstructural information collected from scanning electron microscopy (SEM) was found helpful to explain ferroelectric properties.