Mukul Pastor

Preparation, characterization and dielectric behaviour of some yttrium doped strontium stannates

Samples of Sr(1− 3x/2)YxSnO3 are prepared by usual solid state reaction route. X- ray diffraction studies confirm the formation of single cubic perovskite single phase. The dielectric constant and dielectric loss at 1 kHz were measured in the temperature range from room temperature up to -150†C. The dielectric constant decreases and losses increase with increased yttrium content in the samples. The percentage porosity and unit cell parameters are also calculated for the samples.

Relaxor behavior and dielectric relaxation in Pb(Ba1/3Nb2/3)O3: A phase pure new relaxor material

Pb(Ba1/3Nb2/3)O3 was prepared by two steps solid state reaction route. Material stabilized in orthorhombic perovskite phase with lattice constants a=4.0849(3) A, b=11.8469(4) A, and c=10.6818(9) A. The scanning electron micrograph exhibits heterogeneous grain distribution with average grain size of 1–3 μm. Temperature dependent dielectric constant exhibits a broad peak at 316 K (em=2250) that shows frequency dependent shifts toward higher temperature—typical relaxor behavior. Modified Curie–Weiss law is used to fit the dielectric data that exhibits almost complete diffuse phase transition characteristics. The dielectric relaxation obeys the Vogel–Fulcher relationship with the freezing temperature 286 K. In addition to relaxation observed due to transformation of the material into ergodic relaxor phase below Burn temperature, significant dielectric dispersion is observed in low frequency regime in both components of dielectric response and a small dielectric relaxation peak is observed in the temperature r...

Synthesis and structural characterization of some Pb(B 1 3/t’ Nb2/3)O3 type materials by two-stage solid-state route

Two-stage columbite solid state reaction route has been used for the preparation of Pb(B13/t’Nb2/3)O3 materials (B′ = Mg, Ni and Cd). The columbite precursor phase was structurally characterized using diffraction data. MgNb2O6, NiNb2O6 and CdNb2O6 show orthorhombic structures i.e. pure columbite phase. Final phase materials get stabilized in mixed phase. The diffraction pattern shows that it is a mixture of cubic pyrochlore and perovskite phase. Percentage of perovskite phase was calculated using the band intensities of (110) perovskite and (222) pyrochlore peaks. The calculated percentages show the dominant perovskite phase. Possible reasons for mixed phase are discussed.

Diffused phase transitions in Pb(Zr0.65Ti0.35)O3-Pb(Fe2/3W1/3)O3 multiferroics

The solid solutions of (1−x)Pb(Zr0.65Ti0.35)O3-xPb(Fe2/3W1/3)O3 in different ratios were fabricated by a high-temperature solid-state reaction method using high-purity oxides for possible multi-ferroic applications. Structural analysis using x-ray diffraction powder patterns of the system by Rietveld refinement method exhibits the formation of rhombohedral phase with R3c space group. Detailed studies of dielectric permittivity as a function of temperature of the systems show that the frequency independent dielectric maximum temperature shifts toward room temperature on increasing x. In addition to this, the degree of diffuseness of the permittivity anomaly is more pronounced for higher content of Pb(Fe2/3W1/3)O3, implying the existence of a composition-induced diffuse phase transition for the limited range of compositional ratios. Detailed impedance spectroscopy analysis shows the contributions of grain, grain boundary, and interfacial polarizations in the resistive characteristics and conduction mechanis...

Study of ferroelectric phase transition in new lead free Ba(Ca1/3Nb2/3)O3 compound

ABSTRACT Ba(Ca1/3Nb2/3)O3 (BCN) compound was prepared by solid state reaction route. Structural and electrical analyses were done by X-ray diffraction (XRD), Field effect scanning electron microscope (FESEM), temperature and frequency dependent dielectric and impedance study. Final phase compound shows the formation of single phase cubic crystal system. FESEM micrograph shows the development of the grains in various shapes with different sizes. Relative density of sintered compound found to be 97%. Variation of dielectric constant and dielectric loss with temperature show diffuse ferroelectric characteristics. Electrical ac impedance study reveals that behavior of the electrical resistance and poly dispersive nature of the dielectric relaxation.

Giant dielectric permittivity and weak ferromagnetic behavior in Bi0.5La0.5Fe0.5Cr0.5O3 ceramic

A pervoskite (Bi0.5La0.5)(Fe0.5Cr0.5)O3 (BLFC) nanoparticles were synthesized by high energy ball milling. Rietveld refined X-ray diffraction studies revealed that this compound shows orthorhombic structure with Pbnm space group. The dielectric studies were investigated in wide frequency (102-106) range indicating giant dielectric permittivity behavior similar to LaFeO3 ceramic. The noted dielectric loss relaxation frequency dependent is as following the Arrhenius law can be ascribed as polaronic conduction. Further, magnetic transition at around 337 K and coexistence of weak ferromagnetic and antiferromagnetic behavior is observed below magnetic transition.