scholarly journals Structural, Dielectric and Impedance Spectroscopy of Cerium Doped Bamno3 Single Perovskite

2020 ◽  
Author(s):  
P.G.R. Achary ◽  
Soumakanta Khandai ◽  
Priyabrata Sahoo ◽  
R.K. Bhuyan ◽  
R.N.P. Choudhary ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Dominant Role ◽  
Complex Impedance ◽  
Average Crystallite Size ◽  
Thermally Activated ◽  
Host Materials ◽  
Average Grain Size ◽  
High Temperature Oxide ◽  
Sem Micrograph ◽  
Mixing Method

Abstract The synthesis of barium cerium manganite (BaMn0.9Ce0.1O3) perovskite compound by using a high-temperature oxide mixing method is reported. Structural analysis suggests a hexagonal crystal structure with space group P63/mmc. The average crystallite size and micro-lattice strain of the sample are about 74.4 nm and 0.107% respectively. The SEM micrograph suggests the uniform distribution of grains through well-defined grain boundaries and average grain size is about 11.9 μm. The relaxation time of the electrical process is calculated using the analysis of the real and imaginary parts of the complex impedance data, which suggests that the grain plays a dominant role compare to grain boundaries in defining the conductivity in the sample. Increase of activation energy from 96.8 meV to 689.9 meV with rise of temperature supports thermally activated conduction process. The modulus study suggests the relaxation process is controlled by the immobile charge carriers in the host materials at low-temperature range while controlled by defects at higher temperatures. The presence of semicircular arcs in both Nyquist and Cole-Cole plots confirms the semiconducting nature of the sample and find applications in solid oxide fuel cells and scintillators.

Investigation of Structural and Dielectric Properties of Polycrystalline PbMg1∕3 Ti1∕3W1∕3O3 Tungsten Perovskite

SPIN ◽  
2020 ◽  
Vol 10 (03) ◽  
pp. 2050021
Author(s):  
P. Ganga Raju Achary ◽  
R. N. P. Choudhary ◽  
S. K. Parida
Keyword(s):  
Activation Energy ◽  
Conduction Mechanism ◽  
Complex Impedance ◽  
Interfacial Polarization ◽  
Average Crystallite Size ◽  
Solid State Reaction Method ◽  
Tetragonal Crystal ◽  
Average Grain Size ◽  
Temperature Ranges ◽  
Lead Magnesium

Lead magnesium tungsten titanate PbMg[Formula: see text] Ti[Formula: see text]W[Formula: see text]O3 was prepared by adopting a high-temperature solid-state reaction method. The sample has tetragonal crystal structure having average crystallite size 45.1325[Formula: see text]nm calculated using Scherer’s relation and the average grain size is about 40[Formula: see text]nm from Scanning Electron Microscope (SEM) measurement. Measurements of dielectric permittivity ([Formula: see text]) and loss ([Formula: see text]) have been investigated, both as a function of frequency (1[Formula: see text]kHz to 5[Formula: see text]MHz) and temperature (25–[Formula: see text]C) and the results showed the presence of interfacial polarization of the material. The dielectric spectra with frequency and temperature suggest that the prepared sample is semiconducting in nature following the NTCR behavior. The complex impedance results showed the contribution of grain and grain boundaries in the conduction mechanism. The activation energies were determined from the ac conductivity data in the temperature ranges of 200–[Formula: see text]C and 360–[Formula: see text]C. It has been observed that with the rise of frequency and temperature, the activation energy increases in the sample. The greater value of the activation energy always supports the conduction mechanism due to hopping of the charge carriers. The semicircular arcs of Cole–Cole plots confirm that the sample is semiconducting in nature which supports our dielectric results.

scholarly journals Impedance spectroscopy of nanocrystalline MgFe2O4 and MnFe2O4 ferrite ceramics: Effect of grain boundaries on the electrical properties

2016 ◽  
Vol 48 (1) ◽  
pp. 17-28 ◽  
Author(s):  
Dalibor Sekulic ◽  
Zorica Lazarevic ◽  
Cedomir Jovalekic ◽  
Aleksandra Milutinovic ◽  
Nebojsa Romcevic
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Complex Impedance ◽  
Equivalent Circuit Model ◽  
Average Crystallite Size ◽  
Impedance Analysis ◽  
Ceramic Materials ◽  
Xrd Analysis ◽  
Nanosized Powders ◽  
Complex Impedance Analysis

Two ferrite ceramic materials, MgFe2O4 and MnFe2O4, were successfully fabricated by a conventional sintering of nanosized powders (at 1373 K for 2 h) synthesized by soft mechanochemical route. The particle size and morphology of powders were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD analysis was carried out for the determination of phase purity, crystal structure and average crystallite size of sintered ferrites. Both mechanosynthesized ferrite samples show mean crystallite sizes in the nm-range. Over the frequency range of 100 Hz to 1 MHz, impedance spectra of prepared ferrite ceramics are investigated at and above room temperature. Changes in the impedance plane plots with temperature have been discussed and correlated to the microstructure of materials. An equivalent circuit model is applied to explore the electrical parameters (resistance and capacitance) associated with grains and grain boundaries. Complex impedance analysis indicates the dominance of grain boundary effects which control the overall electrical behaviour of studied ferrites. The decrease in grain boundary resistance with temperature suggests a thermally activated conduction mechanism.

scholarly journals Piezoelectric, impedance, electric modulus and AC conductivity studies on (Bi0.5Na0.5)0.95Ba0.05TiO3 ceramic

2013 ◽  
Vol 7 (2) ◽  
pp. 81-91 ◽  
Author(s):  
Ansu Roy ◽  
Kamal Prasad ◽  
Ashutosh Prasad
Keyword(s):  
Ac Conductivity ◽  
Electric Modulus ◽  
Silicone Oil ◽  
Complex Impedance ◽  
Negative Temperature ◽  
Air Atmosphere ◽  
Average Grain Size ◽  
Modulus Spectroscopy ◽  
Unit Cells ◽  
Sem Micrograph

Lead-free piezoelectric perovskite ceramic (Bi0.5Na0.5)0.95Ba0.05TiO3 (BNT-BT0.05), prepared by conventional high temperature solid state reaction technique at 1160?C/3h in air atmosphere, is investigated by impedance and modulus spectroscopy in a temperature range 35-400?C, over a frequency range 100 Hz-1 MHz. The crystal structure, microstructure, and piezoelectric properties as well as the AC conductivity of the sample were studied. Powder X-ray diffraction pattern derived from the resulting data at the room temperature subjected to Rietveld refinements and Williamson-Hall plot analysis confirmed the formation of phase pure compound with monoclinic unit cells having a crystallite-size ~33.8 nm. Observed SEM micrograph showed a uniform distribution of grains inside the sample having an average grain size ~3 mm. Longitudinal piezoelectric charge coefficient of the sample poled under a DC electric field of ~ 2.5 kV/mm at 80?C in a silicone oil bath was found to be equal to 95 pC/N. The frequency and temperature dependent electrical data analyzed in the framework of AC conductivity, complex impedance as well as electric modulus formalisms showed negative temperature coefficient of resistance (NTCR) character of the material and the dielectric relaxation in the material to be of non-Debye type. Double power law for the frequency-dependence of AC conductivity and Jump Relaxation Model (JRM) were found to explain successfully the mechanism of charge transport in BNT-BT0.05.

High-resolution EM study of submicrometer-grained Al-Mg solid solution alloys

1995 ◽  
Vol 53 ◽  
pp. 524-525
Author(s):  
Z. Horita ◽  
D. J. Smith ◽  
M. Furukawa ◽  
M. Nemoto ◽  
R. Z. Valiev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
High Resolution ◽  
Grain Boundaries ◽  
Energy State ◽  
High Energy ◽  
Grain Structure ◽  
Boundary Structure ◽  
Solid Solution Alloy ◽  
Average Grain Size

It is possible to produce metallic materials with submicrometer-grained (SMG) structures by imposing an intense plastic strain under quasi-hydrostatic pressure. Studies using conventional transmission electron microscopy (CTEM) showed that many grain boundaries in the SMG structures appeared diffuse in nature with poorly defined transition zones between individual grains. The implication of the CTEM observations is that the grain boundaries of the SMG structures are in a high energy state, having non-equilibrium character. It is anticipated that high-resolution electron microscopy (HREM) will serve to reveal a precise nature of the grain boundary structure in SMG materials. A recent study on nanocrystalline Ni and Ni3Al showed lattice distortion and dilatations in the vicinity of the grain boundaries. In this study, HREM observations are undertaken to examine the atomic structure of grain boundaries in an SMG Al-based Al-Mg alloy.An Al-3%Mg solid solution alloy was subjected to torsion straining to produce an equiaxed grain structure with an average grain size of ~0.09 μm.

The effect of the withdrawal speed on properties of nickel oxide thin films

2019 ◽  
Vol 234 (10) ◽  
pp. 647-655
Author(s):  
Zohra Nazir Kayani ◽  
Atiqa Aslam ◽  
Rabia Ishaque ◽  
Syeda Nosheen Zahra ◽  
Hifza Hanif ◽  
...  
Keyword(s):  
Thin Films ◽  
Nickel Oxide ◽  
Band Gap ◽  
Sol Gel ◽  
Average Crystallite Size ◽  
Dip Coating ◽  
Oxide Thin Films ◽  
Withdrawal Speed ◽  
Sem Micrograph ◽  
Nickel Oxide Thin Films

Abstract Nickel oxide thin films have been prepared by sol-gel dip-coating technique on glass substrate. It is shown that nickel oxide thin films have poly crystalline nature. Nickel oxide thin films exhibit high transmission (39–85%) in the wavelength range of 400–900 nm, strong absorption between 300 and 400 nm wavelengths and decrease of band gap values are in the range 3.69–3.27 eV with increase of withdrawal speed. High band gap at low withdrawal speed is because of the small average crystallite size, which decreases with increase in withdrawal speed. The SEM micrograph shows cubic crystallites and surface of thin films become dense, smooth and homogeneous with an increase in withdrawal speed. Assessment of nickel oxide deposition conditions provides gateway for effective and cheap solar cells.

Complex Impedance Spectroscopy of Bi-Substituted Yttrium Iron Garnet (YIG)

2007 ◽  
Vol 336-338 ◽  
pp. 709-711 ◽  
Author(s):  
Hong Jie Zhao ◽  
Ji Zhou ◽  
Zhi Lun Gui ◽  
Long Tu Li
Keyword(s):  
Grain Boundaries ◽  
Yttrium Iron Garnet ◽  
Complex Impedance ◽  
Physical Structure ◽  
Impedance Spectra ◽  
Yttrium Iron ◽  
Electrical Equivalent Circuit ◽  
Small Resistance ◽  
Iron Garnet ◽  
Complex Impedance Spectra

The effects of Bi-substitution on the complex impedance spectra of yttrium iron garnet (YIG) were studied in this paper. The polycrystalline yttrium iron garnet Y2BiFe5O12 (YIG: Bi) and Y3Fe5O12 (YIG) samples were prepared by solid-reaction method. The complex impedance spectra were measured in the frequency range from 1 KHz to 100MHz at several temperatures between 210oC and 500oC. The complex impedance sample shows that the YIG: Bi can be represented by double Cole-Cole semicircles, and the YIG can be represented by a single Cole semicircle. The physical structure of the specimen was visualized as comprising of small resistance grains separated by large resistance grain boundaries in accordance with the impedance spectra observations. The electrical processes in the sample were modeled in the form of an electrical equivalent circuit made up of a series combination of two parallel RC circuits attributed to grains and grain boundaries. The temperature dependence of bulk resistance indicated an evidence of Arrhenius-type thermally activated process, showing a close to linear variation up to a temperature of 740 K.

A Role of Low Energy Grain Boundaries in the Abnormal Grain Growth in Fe-3%Si Alloy

2011 ◽  
Vol 127 ◽  
pp. 89-94 ◽  
Author(s):  
Ye Chao Zhu ◽  
Jiong Hui Mao ◽  
Fa Tang Tan ◽  
Xue Liang Qiao
Keyword(s):  
Grain Boundaries ◽  
Grain Growth ◽  
Electron Backscatter Diffraction ◽  
Dominant Role ◽  
Coincidence Site Lattice ◽  
Diffraction Method ◽  
Abnormal Grain Growth ◽  
Low Energy ◽  
Backscatter Diffraction

Low energy grain boundaries were considered to be important in abnormal grain growth by theoretical deduction. The disorientation angles and coincidence site lattice grain boundaries distribution of more than 20 Goss grains and their neighboring matrix grains in primary recrystallized Fe-3%Si alloy were investigated using an electron backscatter diffraction method. It was found that the frequency of low energy grain boundaries of Goss grains which are more likely to abnormally grow are higher than their neighboring matrix grains, which indicated that low energy grain boundaries play a dominant role in the abnormal grain growth of Fe-3%Si alloy. The result meets well with the abnormal grain growth theory.

Structural and Surface Characteristics of CuO and Pt/CuO Nanostructured Thin Films

2021 ◽  
Vol 14 (5) ◽  
pp. 419-424
Keyword(s):  
Thin Films ◽  
Optical Fibers ◽  
Structural Information ◽  
Surface Characteristics ◽  
X Ray Diffraction ◽  
Phonon Modes ◽  
Silar Method ◽  
Nanostructured Thin Films ◽  
Average Grain Size ◽  
Sem Micrograph

Abstract: The most prominent and utilizable platinum-coated copper Oxide nanostructured thin films are prepared using the SILAR method. Their structural properties have been studied using X-ray diffraction (XRD) and Raman spectroscopy. XRD pattern reveals the phase purity and crystallinity of CuO nanostructures. The average grain size estimated from XRD gives diameters in the range of 14 - 27 nm. Raman spectra explain the structural information of CuO and Pt/CuO nanostructured thin films, in which the peaks observed at 328 cm-1, 609.32 cm-1 and 1141.77 cm-1 are the different phonon modes of CuO. The peak at 2136 cm-1 provides strong evidence for the formation of platinum on CuO nanostructures. The SEM micrograph confirms the floral morphology, which is composed of nano petals. From the observed morphology, it is observed that the deposited thin films such as CuO and Pt/CuO will give interesting applications to our society by being self-cleaning agents, photocatalysts, semiconductor devices, optical fibers, … etc. Keywords: CuO, Pt/CuO, Structural analysis, SILAR, Crystallinity.

Lithium tracer diffusion in near stoichiometric LiNi0.5Mn1.5O4 cathode material for lithium-ion batteries

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Daniel Uxa ◽  
Harald Schmidt
Keyword(s):  
Cathode Material ◽  
Secondary Ion Mass Spectrometry ◽  
Lithium Ion ◽  
Tracer Diffusion ◽  
Side Reactions ◽  
Battery Materials ◽  
Self Diffusion ◽  
Thermally Activated ◽  
Average Grain Size ◽  
And Migration

Abstract The compound LiNi0.5Mn1.5O4 is used as novel cathode material for Li-ion batteries and represents a variant to replace conventional LiMn2O4. For a further improvement of battery materials it is necessary to understand kinetic processes at and in electrodes and the underlying diffusion of lithium that directly influences charging/discharging times, maximum capacities, and possible side reactions. In the present study Li tracer self-diffusion is investigated in polycrystalline sintered bulk samples of near stoichiometric LiNi0.5Mn1.5O4 with an average grain size of about 50–70 nm in the temperature range between 250 and 600 °C. For analysis, stable 6Li tracers are used in combination with secondary ion mass spectrometry (SIMS). The tracer diffusivities can be described by the Arrhenius law with an activation enthalpy of (0.97 ± 0.05) eV, which is interpreted as the sum of the formation and migration energy of a thermally activated Li vacancy.

Mn4+ Activated Deep Red Emitting Perovskite Type Phosphors for Horticulture Lighting

2021 ◽  
Vol 1167 ◽  
pp. 57-66
Author(s):  
Muhammad Khurram ◽  
Florian Baur ◽  
Thomas Juestel
Keyword(s):  
Emission Spectra ◽  
Host Lattice ◽  
Luminescence Spectra ◽  
Quenching Temperature ◽  
Light Emitting ◽  
Thermally Activated ◽  
Host Materials ◽  
Colour Rendering ◽  
Perovskite Type ◽  
Pl Quenching

Red emitting Mn4+ doped oxides are a promising class of materials to improve the colour rendering and luminous efficacy of phosphor-converted light-emitting diodes (pcLEDs). For pcLEDs, the optical properties are crucial w.r.t commercial acceptance. In this work, luminescence spectra and decay curves of Sr2YNbO6, Sr2YTaO6 and Sr2LaNbO6 have been recorded, other Mn4+ doped phosphors show that quenching occurs through thermally activated crossover between the 4T2 excited state and 4A2 ground state. The quenching temperature can be optimized by designing the host lattice in which Mn4+ has a high 4T2 state energy. The main target is to study the influence of the above-mentioned host materials on the emission spectra, PL quenching, and quantum yield of the deep red Mn4+ ion. The present study provides detailed insights into temperature and concentration quenching of Mn4+ emission and can be used to realize superior narrow-band red Mn4+ phosphors for horticultural lighting.

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