I Shivaraja

Effect of Sintering Temperature and Duration on the Formation of Single-Phase Pb0.9Bi0.1Fe0.55Nb0.45O3 Solid Solution

ABSTRACT Effect of sintering temperature and duration on single phase formation and structural properties of Pb0.9Bi0.1Fe0.55Nb0.45O3 (PBFNO) solid solution was investigated. The single step solid state reaction method was adopted to achieve the pure perovskite phase. Calcination was carried out at 700oC for 2 h and sintering at different temperatures as 800o, 850o, 900o, 950o, 1000o and 1050oC for 1 h and also at 800oC for 1-5 h to achieve the single phase in PBFNO solid solution. From the X-ray diffraction studies, it was found that sintering at 800oC for 3 h was optimum for achieving single phase and all the other conditions showed an impurity phase. Rietveld refinement was carried out on single phase PBFNO solid solution by using FullProf Suite, which confirmed the monoclinic structure with Cm space group and the obtained refinement parameters were Rp=15.7; Rw p=20.7, Rexp=16.72, χ2(Chi2)=1.54. The lattice parameters were: a=5.666(3) Å, b=5.667(4) Å, c=4.017(2) Å and α=γ=90o, β=89.943(4)o. Scanning electron micrograph showed an average grain size of ∼2 μm with uniform morphology. All the results clearly revealed the significance of low temperature and short duration sintering to control the single phase in PBFNO solid solution. GRAPHICAL ABSTRACT

Neutron diffraction, Mössbauer and ferroelectric studies on magnetoelectric Pb0.9Bi0.1Fe0.55Nb0.45O3

Pb 0.9Bi0.1Fe0.55 Nb 0.45O3 (PBFNO) multiferroic materialwas synthesized through single step solid state reaction method with low sintering (800 °C for 3 hour) temperature. Single phase was confirmed through the X-Ray Diffraction (XRD), Neutron diffraction (ND) and Scanning Electron Microscopy (SEM) measurements. Rietveld refinement was performed on room temperature (RT) XRD and ND data by considering monoclinic structure with Cm space group. The obtained cell parameters from the refinement of ND data are a = 5.666(3) A, b = 5.667(4) A, c = 4.017(2) A and β = 89.943(4)° and are in good agreement with the XRD refinement data. The RT Mossbauer spectroscopy was used to investigate the magnetic ordering of PBFNO and it shows the paramagnetic behavior with the presence of Fe3+ states. RT ferroelectric (P-E) loops confirmed the existence of ferroelectric ordering in the PBFNO. The RT ferroelectric and antiferromagnetic properties are the evidence of magnetoelectric coupling.

Neutron diffraction, Mössbauer and electron paramagnetic resonance studies of Pb0.8Bi0.2Fe0.6Nb0.4O3 multiferroic

The Pb0.8Bi0.2Fe0.6Nb0.4O3 (PFN-BFO) multiferroic solid solution was synthesized by single step solid state reaction method with low calcination (700 °C/2h) and sintering (800 °C/3h) temperatures. Single phase formation was confirmed through X Ray Diffraction (XRD) and Neutron Diffraction (ND) at room temperature (RT). The structural analysis was carried out by Rietveld refinement through the Fullprof program. Refined XRD and ND patterns confirms the monoclinic structure with Cm space group and obtained cell parameters from the ND data are a = 5.6449(8) A, b = 5.6536(5) A, c = 4.0017(6) A and β = 89.930(4)°. ND data at RT exhibits G-type antiferromagnetic structure. The Mossbauer and Electron Paramagnetic Resonance (EPR) spectroscopy studies were carried out at RT. The isomer shift and the quadrupole splitting of the Mossbauer spectra confirm the Fe in +3 states. An EPR spectrum shows a single broad slight asymmetric line, is an evidence of Fe in +3 states. ND, Mossbauer and EPR studies are the clear evid...

Structural, Magnetic and Dielectric Studies of Pb0.9Bi0.1Fe0.55Nb0.45O3 Multiferroic Solid solution

Single phase Pb0.9Bi0.1Fe0.55Nb0.45O3 (PFN-BFO) multiferroic solid solution was synthesized through single step solid state reaction method using low temperature annealing technique. The crystal structure, microstructure, magnetic and dielectric properties of PFN-BFO solid solution were investigated at room temperature (RT). Sintered samples were then subjected to XRD analysis and it revealed the formation of single phase without any impurities. The structural analysis was carried out by Rietveld Refinement technique through the Full Prof suite. The RT Rietveld refined XRD pattern confirms the monoclinic structure with Cm space group and obtained cell parameters are a = 5.666(3)A, b = 5.667(4)A, c = 4.017(2)A and p = 89.943(4)°. The surface morphology of the sample was studied by Scanning electron microscope (SEM) and average grain size was estimated to be ~5μm. M-H curve shows the weak ferromagnetic kind of behaviour with antiferromagnetic ordering. Room temperature dielectric constant, loss tangent and impedance spectroscopic data were measured at different frequencies (100Hz - 5MHz). The impedance spectroscopy reveals the contribution from the grains towards the electrical parameters.

Low temperature dielectric and impedance studies on magnetoelectric Pb(Fe0.5Nb0.5)O3 ceramic

The structural, microstructural, low temperature dielectric and impedance properties of Pb(Fe0.5Nb0.5)O3 (PFN) ceramic prepared by single step solid-state reaction method have been investigated. Processing parameters such as calcination, sintering temperature and sintering durations were optimized to get better dielectric properties. It was found that the above ceramics sintered at 1050 °C for 4 hr exhibited single phase, maximum density and uniform microstructure. X-ray diffraction (XRD) and neutron diffraction (ND) reveals that the system exhibit single phase without any kind of secondary phases at room temperature (RT) with monoclinic crystal structure (Cm). Surface morphology of the compounds was studied by Scanning electron microscope (SEM). Impedance spectroscopy is used to study the electrical behaviour of PFN in the frequency range from 100Hz to 1MHz and in the temperature range from 120 to 293 K. The frequency-dependent electrical data are analyzed by impedance formalisms. The complex impedance s...

Low temperature dielectric and conductivity relaxation studies on magnetoelectric Pb(Fe2/3W1/3)O3

The single phase perovskite Pb(Fe2/3W1/3)O3 [PFW] was synthesized by modified low – temperature (sintering at 850°C) solid-state reaction. Rietveld refinement ofroom temperature (RT) X-ray diffraction (XRD) and neutron diffraction (ND) patterns of the samples confirm the single phase formation with cubic structure (Pm-3m). Surface morphology of the compounds was studied by Scanning electron microscope (SEM) and average grain size was estimated to be ∼2 µm. The RT dielectric properties of PFW ceramic are studied as a function of frequency from 100 - 1MHz. The temperature dependent (120 – 293K) dielectric properties were studied at few selected frequencies. We found the frequency dependent dielectric constant shows increasing trend with increase in temperature from 120 – 293K, with minimum dielectric loss. The frequency dependence of dielectric loss shows a maximum in between 10 Hz and 1 kHz, confirms the extrinsic phenomena like interfacial polarization due to space charge accumulation at grain boundaries. Impedance spectroscopy is used to study the electrical behaviour of PFW in the frequency range from 100 to 1MHz and in the temperature range from 120 - 293 K. The frequency-dependent electrical data are analysed by impedance formalisms and shows the relaxation (conduction) mechanism in the sample. We suggest this low temperature sintered PFW is a suitable candidate for the multilayer ceramic capacitorsandrelated negative temperature coefficient of resistance type (NTCR) behavior like that of semiconductors.