Dielectric properties of Ba3Sr2DyTi3V7O30 ceramics

Open Physics ◽  
2010 ◽  
Vol 8 (4) ◽  
Author(s):  
Priyadarshini Sahoo ◽  
Anuradha Panigrahi ◽  
Sunanda Patri ◽  
Rasm Choudhary
Keyword(s):  
Room Temperature ◽  
Paraelectric Phase ◽  
Tungsten Bronze ◽  
Polycrystalline Sample ◽  
Dielectric Anomaly ◽  
Tungsten Bronze Structure ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Oxygen Ion ◽  
Temperature Surface

AbstractA polycrystalline sample, Ba3Sr2DyTi3V7O30, with tungsten bronze structure was prepared by a mixed-oxide method at high temperature (950°C). Preliminary structural analysis of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound was studied by scanning electron microscopy. The dielectric anomaly at 321°C may be attributed to the ferro-paraelectric phase transitions. This was also confirmed from the appearance of a hysteresis loop. The nature of variation of the ac conductivity and value of activation energy at different temperature regions, suggest that the conduction process is of mixed-type (i.e., ionic-polaronic and space charge generated from the oxygen ion vacancies).

IMPEDANCE SPECTROSCOPY STUDY OF NaCa2Nb5O15 CERAMICS

2009 ◽  
Vol 23 (01) ◽  
pp. 97-109 ◽  
Author(s):  
BANARJI BEHERA ◽  
P. NAYAK ◽  
R. N. P. CHOUDHARY
Keyword(s):  
Electrical Transport ◽  
Complex Modulus ◽  
Complex Impedance ◽  
Tungsten Bronze ◽  
Polycrystalline Sample ◽  
Transport Processes ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Wide Range ◽  
Increasing Temperature

Polycrystalline sample of NaCa 2 Nb 5 O 15 was prepared by a high-temperature solid-state reaction technique. Preliminary X-ray structural analysis exhibits the orthorhombic crystal structure of the compound at room temperature. Detailed dielectric studies of NaCa 2 Nb 5 O 15 over a wide range of temperature (31–500°C) and frequency (102–106 Hz) did not show any dielectric anomaly (or ferroelectric phase transition) as observed in other members of the tungsten bronze structural family. However, the low loss tangent and dielectric constant increase with increasing temperature. Complex impedance and modulus plots (at different temperature and frequency) show the existence of non-Debye type of relaxation process in the compound. Complex modulus spectrum shows only grain contribution in the compound. Electric modulus analysis suggests that a possible hopping mechanism is evident for electrical transport processes in the system. Studies of AC conductivity with frequency suggest that the material obeys Jonscher's universal power law.

Structural, Dielectric and Electrical Studies of Ba4CaRTi3Nb7O30 (R = Eu, Dy) Ferroelectric System

2013 ◽  
Vol 547 ◽  
pp. 41-48 ◽  
Author(s):  
Prasun Ganguly ◽  
A.M. Biradar ◽  
A.K. Jha
Keyword(s):  
Single Phase ◽  
Microstructural Analysis ◽  
Tungsten Bronze ◽  
Negative Temperature ◽  
Xrd Analysis ◽  
Solid State Reaction Method ◽  
X Ray Diffraction ◽  
Orthorhombic Crystal ◽  
Paraelectric Phase Transition ◽  
Orthorhombic Crystal Structure

The polycrystalline samples of Ba4CaRTi3Nb7O30 (R = Eu, Dy), members of tungsten-bronze family, were prepared by high-temperature solid state reaction method and studied for their dielectric and electrical properties. X-ray diffraction (XRD) analysis reveals the formation of single-phase compounds having orthorhombic crystal structure at room temperature. Microstructural analysis by scanning electron microscope (SEM) shows that the compounds have well defined grains, which are distributed uniformly throughout the sample. Detailed dielectric properties of the compounds as a function of frequency and temperature show that the compounds undergo non-relaxor kind of ferroelectric-paraelectric phase transition of diffuse nature. Ferroelectric, piezoelectric and pyroelectric studies of the compounds have been discussed in this paper. The temperature dependence of dc conductivity of the compounds have been investigated. The conductivity study over a wide temperature range suggests that the compounds have negative temperature coefficient of resistance (NTCR) behaviour.

Structural and electrical properties of KCa2Nb5O15 ceramics

Open Physics ◽  
2008 ◽  
Vol 6 (2) ◽  
Author(s):  
Banarji Behera ◽  
Pratibindhya Nayak ◽  
Ram Choudhary
Keyword(s):  
Electrical Properties ◽  
Temperature Variation ◽  
Electrical Transport ◽  
Room Temperature ◽  
Complex Impedance ◽  
Tungsten Bronze ◽  
Transport Processes ◽  
Relaxation Processes ◽  
Orthorhombic Crystal Structure ◽  
Grain Distribution

AbstractA polycrystalline sample of KCa2Nb5O15 with tungsten bronze structure was prepared by a mixed oxide method at high temperature. A preliminary structural analysis of the compound showed an orthorhombic crystal structure at room temperature. Surface morphology of the compound shows a uniform grain distribution throughout the surface of the sample. Studies of temperature variation on dielectric response at various frequencies show that the compound has a transition temperature well above the room temperature (i.e., 105°C), which was confirmed by the polarization measurement. Electrical properties of the material have been studied using a complex impedance spectroscopy (CIS) technique in a wide temperature (31–500°C) and frequency (102–106 Hz) range that showed only bulk contribution and non-Debye type relaxation processes in the material. The activation energy of the compound (calculated from both the loss and modulus spectrum) is same, and hence the relaxation process may be attributed to the same type of charge carriers. A possible ‘hopping’ mechanism for electrical transport processes in the system is evident from the modulus analysis. A plot of dc conductivity (bulk) with temperature variation demonstrates that the compound exhibits Arrhenius type of electrical conductivity.

STRUCTURAL AND IMPEDANCE CHARACTERISTICS OF KPb2V5O15

2011 ◽  
Vol 25 (28) ◽  
pp. 3745-3753
Author(s):  
P. S. DAS ◽  
P. K. CHAKRABORTY ◽  
BANARJI BEHERA ◽  
R. N. P. CHOUDHARY
Keyword(s):  
Boundary Effect ◽  
Complex Impedance ◽  
Negative Temperature ◽  
Polycrystalline Sample ◽  
Homogeneous Distribution ◽  
Orthorhombic Crystal ◽  
Ac Electrical Conductivity ◽  
Orthorhombic Crystal Structure ◽  
Impedance Characteristics ◽  
Sem Micrograph

The polycrystalline sample of KPb 2 V 5 O 15 was prepared by a mixed-oxide method relatively at low temperature (i.e., 550°C). X-ray diffraction studies of the compound showed the formation of single phase orthorhombic crystal structure at room temperature. SEM micrograph showed the homogeneous distribution of grains throughout the sample. Electric properties were analyzed using the complex impedance spectroscopy. The modulus plot showed the presence of both the grain and grain boundary effect. The bulk impedance evaluated from the Nyquist plots was observed to decrease with the rise in temperature, showing a negative temperature coefficient of resistance. The variation of AC electrical conductivity (σ AC ) was measured in a wide temperature (30–500°C) and frequency (102–106 Hz) range. The activation energy of the compound calculated from both the impedance and modulus spectrum was found to be the same.

Rietveld Refinement and DC Conductivity of Na0.5K0.5NbO3 Ceramics

2012 ◽  
Vol 585 ◽  
pp. 210-213 ◽  
Author(s):  
Monica Sindhu ◽  
N. Ahlawat ◽  
Sujata Sanghi ◽  
Ashish Agarwal ◽  
A. Ashima ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rietveld Refinement ◽  
Base Material ◽  
Polycrystalline Sample ◽  
Solid State Reaction Method ◽  
Dc Conductivity ◽  
Potassium Sodium Niobate ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Refinement Method

Potassium Sodium Niobate, Na0.5K0.5NbO3 is a promising base material for lead free piezoceramics. The polycrystalline sample Na0.5K0.5NbO3 was synthesized using solid state reaction method. The crystal structure and phase purity was studied by XRD and analysed using Rietveld refinement method. Good agreement was observed between the observed and calculated patterns in Rietveld refinement. The refinement inferred orthorhombic crystal structure with Amm2 space group. The impedance spectroscopy of the sample was performed in frequency range 10 Hz to 7 MHz in temperature range 573K to 703K. The activation energy was obtained to be 0.67eV from the reciprocal temperature variation of dc conductivity which follows the Arrhenius law.

scholarly journals Ferroelectric Properties ofNa2Pb2R2W2Ti4V4O30(R = Dy, Pr) Ceramics

2007 ◽  
Vol 2007 ◽  
pp. 1-5 ◽  
Author(s):  
Piyush R. Das ◽  
Banarji Behera ◽  
R. N. P. Choudhary ◽  
B. K. Samantray
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Ferroelectric Properties ◽  
X Ray Diffraction ◽  
Orthorhombic Crystal ◽  
Solid State Reaction Technique ◽  
Orthorhombic Crystal Structure ◽  
Preparation Conditions ◽  
Polarization Study ◽  
Ferroelectric Phase Transitions

The polycrystalline samples ofNa2Pb2R2W2Ti4V4O30(R = Dy, Pr) were prepared by low-temperature, (i.e., at650∘C) solid-state reaction technique. The preparation conditions have been optimized using thermogravimetry analysis (TGA) technique. X-ray diffraction (XRD) studies of the compounds showed the formation of a single-phase orthorhombic crystal structure at room temperature. Studies of dielectric properties (ɛrand tanδ) of the compounds at frequencies 10, 100, and 1000 kHz in a wide temperature range (room temperature–500∘C) exhibit ferroelectric phase transitions at132∘Cfor NPDWTV and at122∘Cfor NPPWTV of diffuse type. Ferroelectric properties of the materials are confirmed by polarization study.

Ba6CoNb9O30 and Ba6FeNb9O30: Two New Tungsten-Bronze-Type Ferroelectrics. Centrosymmetry of Ba5.2K0.8U2.4Nb7.6O30 at 300 K

1997 ◽  
Vol 30 (4) ◽  
pp. 495-501 ◽  
Author(s):  
M. C. Foster ◽  
G. R. Brown ◽  
R. M. Nielson ◽  
S. C. Abrahams
Keyword(s):  
Phase Transition ◽  
Spontaneous Polarization ◽  
Diffuse Phase Transition ◽  
Room Temperature ◽  
Tungsten Bronze ◽  
Dielectric Anomaly ◽  
Structural Refinement ◽  
Space Group ◽  
Atomic Displacements ◽  
Diffuse Phase

Ba6CoNb9O30 and Ba6FeNb9O30 in space group P4bm are shown to satisfy the structural criteria for ferroelectricity. Ba6CoNb9O30 undergoes a diffuse phase transition at 660 (11) K, as observed calorimetrically, in addition to a dielectric permittivity anomaly with an onset temperature of 685 (10) K. The demonstration of dielectric hysteresis at room temperature under the application of a varied DC field reaching a maximum of ± 300 kV m−1, corresponding to a spontaneous polarization of 1.2 (5) × 10−2C m−2, provides unambiguous verification that it is a new ferroelectric. Ba6FeNb9O30 also undergoes a diffuse phase transition at 605 (16) K, with a dielectric anomaly at 583 (5) K, and exhibits dielectric hysteresis at room temperature under a varied DC field ranging to ± 310 kV m−1 corresponding to a spontaneous polarization of 2.2(5) × 10−2Cm−2; it too is demonstrably a new ferroelectric. Although Ba5.2K0.8U2.4Nb7.6O30 has also been reported in space group P4bm, all atomic displacements from the corresponding centrosymmetric positions are less than their refined root-mean-square thermal or static amplitudes. Such an arrangement is likely to be thermodynamically unstable. Either its space group has been incorrectly assigned, and reinvestigation will show the space group is P4/mbm, or the structural refinement is incomplete.

Preparation, Structural, Optical, Electrical, and Magnetic Characterisation of Orthorhombic GdCr0.3Mn0.7O3 Multiferroic Nanoparticles

2017 ◽  
Vol 72 (1) ◽  
pp. 87-95
Author(s):  
Deepa Singh ◽  
K.K. Bamzai
Keyword(s):  
Activation Energy ◽  
Ac Conductivity ◽  
Room Temperature ◽  
Magnetic Behaviour ◽  
X Ray Diffraction ◽  
Orthorhombic Crystal ◽  
Sem Images ◽  
Chemical Route ◽  
Orthorhombic Crystal Structure ◽  
Universal Power Law

AbstractIn this article, chromium-doped gadolinium manganate (GdCr0.3Mn0.7O3) nanoparticles has been prepared by wet-chemical route in order to investigate their structural, optical, electrical, and room temperature magnetic properties. Microstructural and compositional analyses have been carried out by X-ray diffraction and scanning electron microscopy (SEM). Synthesised material is found to be in orthorhombic crystal structure with Pbnm space group. The spherical morphology of the nanoparticles has been examined from the SEM images. Functional groups have been identified using Fourier transform infrared spectroscopy. Dielectric constant, dielectric loss, AC conductivity (σac), and activation energy in the range of 1 kHz–1 MHz from room temperature to high temperature (400°C) have been investigated. The frequency dependence of AC conductivity obeys the universal power law. The value of activation energy depends on increase in frequency. Room temperature magnetic behaviour suggests the material to be paramagnetic in nature.

The Effect of Pressure on the Raman and Absorption Spectra of PrCl3, PrBr3, and NdBr3

1989 ◽  
Vol 43 (6) ◽  
pp. 1038-1045 ◽  
Author(s):  
W. R. Wilmarth ◽  
G. M. Begun ◽  
R. G. Haire ◽  
J. P. Young ◽  
J. R. Peterson
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Phase Transformation ◽  
Solid State ◽  
Room Temperature ◽  
Orthorhombic Structure ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Hexagonal Form ◽  
Type Orthorhombic

Solid-state absorption and Raman phonon spectroscopic investigations of PrCl3, PrBr3, and NdBr3 under high pressure have been carried out at room temperature. These studies showed that the UCl3-type hexagonal form of PrCl3 and PrBr3 converts with the application of pressure to the PuBr3-type orthorhombic crystal structure. The absorption and Raman spectra obtained from PrBr3 and NdBr3 at pressures above ∼260 kbar exhibit differences from spectra obtained at lower pressures, where they exhibit the PuBr3-type orthorhombic structure. These spectral differences suggest that a phase transformation might have taken place to an as-yet-unidentified crystal structure.

Bi-Sr-Ca-Cu-O SURFACE STUDIED BY MEANS OF SCANNING TUNNELLING MICROSCOPE

1989 ◽  
Vol 03 (03) ◽  
pp. 235-239
Author(s):  
A. WITEK ◽  
A. DABKOWSKI ◽  
J. RAULUSZKIEWICZ
Keyword(s):  
Crystal Structure ◽  
Surface Topography ◽  
Room Temperature ◽  
Unit Cell ◽  
Scanning Tunnelling Microscope ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Natural Surface ◽  
Scanning Tunnelling ◽  
Surface Images

Surface topography of the high-T c superconductor BiSrCaCu 2 O x has been investigated by means of scanning tunnelling microscope. The measurements were performed on the natural surface of ceramics material in air at room temperature. It can be deduced from the surface images, that bulk orthorhombic crystal structure extends to the surface. The surface seems to be uniform metallic in character and not drastically contaminated. Regular steps observed on the surface correspond to the dimension of the unit cell in z direction or its multiples.

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