R.K. Parida; B.N Parida; R. K. Bhuyan; S. K. Parida
Abstract
The La modified bismuth ferrite perovskite Bi0.6La0.4FeO3 (BLF) is prepared by cost-effective high solid-solution casting technique. Formation of composite is checked through X-ray diffraction and also notable that there is phase transition from rhombohedral (R3c) to orthorhombic (Pbnm). The average ...
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The La modified bismuth ferrite perovskite Bi0.6La0.4FeO3 (BLF) is prepared by cost-effective high solid-solution casting technique. Formation of composite is checked through X-ray diffraction and also notable that there is phase transition from rhombohedral (R3c) to orthorhombic (Pbnm). The average crystalline size (DSC) and mechanical lattice strain are 63.8 nm and 0.147% respectively as calculated by Williamson-Hall method. The frequency bands corresponding to Bi-O, LaO, and FeO stretching vibration confirm that La+3 ions completely incorporate the Bi+3 ions in the A-site of the single perovskite. The SEM micrograph suggests that the sample has distinct grains and well-defined grain boundaries and the average grain size (DSEM) is about 13.9 μm. The rate of agglomeration that acquire in the sample (DSEM/ DSC = 219) confirms the excellent connectivity of grains which stands possible reason for the high dielectric and conductivity. The impedance analysis provided the fact that bulk resistance (Rb) decreases from 6.662 x 105 Ω at 25 0 C to 1.000 x 10-2 Ω at 350 0 C; suggesting NTCR behaviour of the material. The activation energy increases from 201 meV to 677meV with temperature supports a thermally activated conduction mechanism. The thermally activated relaxation process is controlled by the immobile charge carriers at lower temperature range while controlled by defects at higher temperatures which suggests the presence of hopping mechanism. The gap between the peak of 𝐙′′and 𝐌′′ is becoming wide with temperature suggests a non-Debye type character. The semicircular arcs in both Nyquist plots and Cole-Cole plots are confirming the semiconductor nature.
Ramakanta Naik
Abstract
The present paper highlights the optical properties change in thermally evaporated As40Sb15Se45 amorphous film of 800 nm thickness with laser irradiation. The as-prepared and illuminated films were studied by X-ray diffraction, Energy dispersive X-ray analysis. The optical properties were calculated ...
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The present paper highlights the optical properties change in thermally evaporated As40Sb15Se45 amorphous film of 800 nm thickness with laser irradiation. The as-prepared and illuminated films were studied by X-ray diffraction, Energy dispersive X-ray analysis. The optical properties were calculated from the transmission spectra obtained from Fourier Transform Infrared Spectroscopy. The band gap is decreased by 0.22 eV due to photo induced effects causing photo darkening. The refractive index is found to be increased due to increase in structural disordering. These optical properties changes are due to the change of homopolar bond densities which can be seen from the core level peak shifting in XPS spectra. The optical constants such as refractive index, band gap of the material plays a major role in the preparation of the device for a particular wavelength. Selecting suitable pairs of chalcogenide glasses with different optical gaps, one can modify the parameters of the light sensitive layers and use them for optical recording.
Nawnit Kumar; Patri Tirupathi; Bineet Kumar; Mukul Pastor; A. C. Pandey; R. N. P. Choudhary
Abstract
We reports structural, microstructural and dielectric characteristics of Sr 2+ doped PZT (50/50) ceramic. X-ray diffraction reveals that the system exhibit coexistence of two phases (Tetragonal and rhombohedral) at room temperature. Typical relaxor behavior was observed by the dielectric studies and ...
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We reports structural, microstructural and dielectric characteristics of Sr 2+ doped PZT (50/50) ceramic. X-ray diffraction reveals that the system exhibit coexistence of two phases (Tetragonal and rhombohedral) at room temperature. Typical relaxor behavior was observed by the dielectric studies and confirmed by Vogul-Fulcher fitting. The observed relaxor was predicted as existence of nanopolar regions due to short range ordering in presence of oxygen vacancies. The evidence for oxygen vacancies was studied by conductivity and polarization studies. Moreover, at 270 °C one more phase transition is noted which was ascribed to structural phase transition. Present study has scientific significance to distinguish the performance of oxygen vacancies in ferroelectric materials.
Venkata Ramana Mudinepalli; N. Ramamanohar Reddy; Wen-Chin Lin; K.V. Siva Kumar; B.S. Murty
Abstract
This work focuses on the high temperature dielectric and mechanical spectroscopic properties of lead free relaxor Sodium Bismuth Titanate (NBT) ceramics, fabricated by conventional ceramic double sintering method. Systematic measurements of dielectric and mechanical properties have been performed as ...
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This work focuses on the high temperature dielectric and mechanical spectroscopic properties of lead free relaxor Sodium Bismuth Titanate (NBT) ceramics, fabricated by conventional ceramic double sintering method. Systematic measurements of dielectric and mechanical properties have been performed as a function of temperature. A sequence of phase transitions has been studied by both dielectric and anelastic measurements. Three internal friction peaks were observed near 350, 200 and 120 °C. The 350 °C-peak corresponds to a transition associated with the tetragonal (P < /em>4bm) to rhombohedral (R3c) phase, and the 200 °C-peak is related to the ferroelectric to antiferroelectric phase transition. The 120 °C-peak could be ascribed to the interaction between the domain walls and the diffusion of oxygen vacancies in the domains.
I. Danilenko; F. Glazunov; T. Konstantinova; I. Yashchyshyn; V. Burkhovetski; G. Volkova
Abstract
The structure formation of yttria stabilized zirconia - nickel oxide composites sintered in air and argon atmosphere were studied. It was shown that the crack propagation in 3Y-TZP ceramics greatly inhibited by creation of composite structure by addition of NiO particles and sintering at 1500 o C in ...
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The structure formation of yttria stabilized zirconia - nickel oxide composites sintered in air and argon atmosphere were studied. It was shown that the crack propagation in 3Y-TZP ceramics greatly inhibited by creation of composite structure by addition of NiO particles and sintering at 1500 o C in argon atmosphere. Prevention of formation of the monoclinic phase of zirconia was conditioned by sintering composite under argon. Increasing of K1C value was found as in sample shell as in sample core of composite, in comparison with matrix 3Y-TZP ceramics. The increasing of K1C value of obtained intergranular type of composite structure cannot be explained by crack deflection and crack bridging processes by Ni and NiO particles, respectively. The possible explanation of K1C value increasing is the intensification of phase transformation toughening of zirconia by formation of metastable tetragonal phase depleted by Y 3+ ions. The reversibly dissociation of NiO on Ni and oxygen in neutral atmosphere provided the formation of cubic phase and Y 3+ depleted tetragonal phase. Internal oxidation of Ni during cooling leads to formation metastable tetragonal phase in depleted Y 3+ zirconia grains. The formation of NiO particles during cooling lead to emergence of large compressive stresses, which also increased the metastability of tetragonal zirconia grains, depleted of Y 3+ ions.
Arvind Kumar; S. K. Mishra
Abstract
In the present work, detailed investigation of dielectric, piezoelectric and ferroelectric properties of Nb and Fe co-doped PZT ceramic near the MPB composition has been carried out. Pb1-3x/2 Fex(Zr0.52Ti0.48)1-5y/4 NbyO3 (PFZTN) ceramics for x = 1- 6 mol% and y = 5.50 mol% have been prepared by a semi-wet ...
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In the present work, detailed investigation of dielectric, piezoelectric and ferroelectric properties of Nb and Fe co-doped PZT ceramic near the MPB composition has been carried out. Pb1-3x/2 Fex(Zr0.52Ti0.48)1-5y/4 NbyO3 (PFZTN) ceramics for x = 1- 6 mol% and y = 5.50 mol% have been prepared by a semi-wet route. X-ray diffraction studies confirm the formation of single phase perovskite structure. It is shown that Fe doping in PZNT improves the dielectric, ferroelectric and piezoelectric properties of ceramics. It has been found that at room temperature, dielectric constant and d33 start to increase up to the composition x = 0.05 and thereafter decrease. The maximum value of dielectric constant and d33 has been found for the composition x = 0.05. It has been shown that doping of Fe does not affect over the transition temperature uptown x = 0.04. The value of remnant polarization is of the order of 11.62 µC/cm 2 at x= 0.04. The investigated material seems to be promising candidate for multilayer capacitor applications.
Samir Mansour; Naima Boutarek; Sif Eddine Amara
Abstract
The present work is a continuation of research on alloys based on iron, with the aim to understanding the solidification behaviour of Fe-V-Nb alloys. Solidification sequences are proposed in relation to the observed microstructures for Fe-V-Nb synthesis alloys. Fe-V-Nb binary alloys with different concentrations ...
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The present work is a continuation of research on alloys based on iron, with the aim to understanding the solidification behaviour of Fe-V-Nb alloys. Solidification sequences are proposed in relation to the observed microstructures for Fe-V-Nb synthesis alloys. Fe-V-Nb binary alloys with different concentrations are arc melted and characterized systematically by means of differential thermal analysis, optical and scanning electron microscopy coupled to an energy dispersive X-Ray microprobe analysis, quantitative XRF spectrometry and X-Ray diffraction. In the present work, the thermal and microsructural behavior of Fe–V –Nb alloys with different concentrations have been studied with the aim of answering some questions and especially paying attention to the microstructures and temperature transition. Two primary surfaces are identified: a(Fe) and Fe2Nb. Moreover, one invariant line is also identified as a binary eutectic reaction (L « a + Fe2Nb), which is clearly shown according to the observed microstructure. In perspective, other shades of this ternary alloy will be studied for a path projection of liquidus surface.
P. Venkatesu; K. Ravichandran; B. K. Reddy
Abstract
Nanocrystalline samples of Cadmium Sulphide (CdS) were prepared with different Manganese (Mn) doping concentrations (0-10 at.%) through chemical route using thiophenol as a capping agent. Fourier Tranform Infrared Spectroscopy (FT-IR) study disclosed the presence of capping agent on the surface of the ...
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Nanocrystalline samples of Cadmium Sulphide (CdS) were prepared with different Manganese (Mn) doping concentrations (0-10 at.%) through chemical route using thiophenol as a capping agent. Fourier Tranform Infrared Spectroscopy (FT-IR) study disclosed the presence of capping agent on the surface of the samples. X-ray diffraction (XRD) analysis showed phase transition from hexagonal to cubic phase beyond 8 at.% of Mn doping and grain size in the range of 13-30 nm. Micro structural study by High Resolution Transmission Electron Microscopy (HRTEM) confirmed phase transition and quasi-spherical particles having size in 15-50 nm range with small grains distributed on the surface of the particles. A blue shift in the band gap energy of the samples was indicated in optical absorption study and the band gap was found to vary nonlinearly with Mn content. Studies on electrical properties of the samples using a complex impedance spectroscopy (CIS) technique showed a decrease in the bulk resistance with increase in Mn concentration. Further, the nature of cole-cole plots (Nyquist plots) revealed the presence of bulk and grain boundary effects in the samples in consistent with HRTEM results. These crystalline quasi-spherical nanoparticles of CdS:Mn seems to be one of the promising candidates for modern age opto-electronics and biomedical applications.
T. Prakash
Abstract
Copper (I) iodide (CuI) has been synthesized by wet chemical route at room temperature using freshly prepared copper oxide (CuO) as a precursor. The as-prepared CuI exists in g - phase and it undergoes two structural phase transition between room temperature and its melting point. Differential scanning ...
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Copper (I) iodide (CuI) has been synthesized by wet chemical route at room temperature using freshly prepared copper oxide (CuO) as a precursor. The as-prepared CuI exists in g - phase and it undergoes two structural phase transition between room temperature and its melting point. Differential scanning calorimetry measurement in both heating and cooling cycles confirms its structural reversible phase transitions from g b phase then from b to a phase. In order to understand the underlying physical properties before and after transitions induced by temperature was studied by X-ray diffraction, scanning electron microscopy, fluorescence, fourier transformed infrared spectroscopy and thermal analysis using TGA, DTA and DSC.
