scholarly journals Dielectric Properties of PbNb2O6 up to 700°C from Impedance Spectroscopy

2013 ◽  
Vol 2013 ◽  
pp. 1-15 ◽  
Author(s):  
Kriti Ranjan Sahu ◽  
Udayan De
Keyword(s):  
Impedance Spectroscopy ◽  
Curie Temperature ◽  
Piezoelectric Materials ◽  
Rhombohedral Phase ◽  
Orthorhombic Phase ◽  
Wide Band ◽  
Rietveld Analysis ◽  
Activation Energies ◽  
Complete Analysis ◽  
Dc Conductivities

Piezoelectric materials have wide band gap and no inversion symmetry. Only the orthorhombic phase of lead metaniobate (PbNb2O6) can be ferroelectric and piezoelectric below Curie temperature, but not the rhombohedral phase. High temperature piezoelectric applications in current decades have revived international interest in orthorhombic PbNb2O6, synthesis of which in pure form is difficult and not well documented. Second problem is that its impedance spectroscopy (IS) data analysis is still incomplete. Present work attempts to fill up these two gaps. Presently found synthesis parameters yield purely orthorhombic PbNb2O6, as checked by X-ray Rietveld analysis and TEM. Present 20 Hz to 5.5 MHz IS from room temperature to 700°C shows its ferroelectric Curie temperature to be one of the highest reported, >574°C for 0.5 kHz and >580°C for 5.5 MHz. Dielectric characteristics and electrical properties (like capacitance, resistance and relaxation time of the equivalent CR circuit, AC and DC conductivities, and related activation energies), as derived here from a complete analysis of the IS data, are more extensive than what has yet been reported in the literature. All the properties show sharp changes across the Curie temperature. The temperature dependence of activation energies corresponding to AC and DC conductivities has been reexamined.

scholarly journals Dielectric Properties of Rhombohedral PbNb2O6

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Kriti Ranjan Sahu ◽  
Udayan De
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
High Temperature ◽  
Single Phase ◽  
Rhombohedral Phase ◽  
Orthorhombic Phase ◽  
Dielectric Materials ◽  
Rietveld Analysis ◽  
Bulk Resistance ◽  
Relaxation Time Constant

Dielectric materials are needed in many electrical and electronic applications. So, basic characterizations need to be done for all dielectrics. PbNb2O6 (PN) is ferroelectric and piezoelectric only in its orthorhombic phase, with potential high temperature applications. So, its rhombohedral phase, frequently formed as an undesirable impurity in the preparation of orthorhombic PN, has been ignored with respect to possible dielectric characterizations. Here, essentially single phase rhombohedral PN has been prepared, checking structure from XRD Rietveld Analysis, and the real and imaginary parts of permittivity measured in an Impedance Spectrometer (IS) up to ~700∘C and over 20 Hz to 5.5 MHz range, for heating and some cooling runs. Variations, with temperature, of relaxation time constant (τ), AC and DC conductivity, bulk resistance, activation energy and capacitance have been explored from our IS data.

scholarly journals High Temperature XRD of Phase Transition in Piezoelectric PbNb2O6 across its Curie Temperature

2016 ◽  
Vol 13 (1) ◽  
pp. 14-20 ◽  
Author(s):  
Udayan De ◽  
Kriti Ranjan Sahu ◽  
Keka R Chakraborty
Keyword(s):  
Phase Transition ◽  
High Temperature ◽  
Curie Temperature ◽  
Piezoelectric Materials ◽  
Orthorhombic Phase ◽  
X Ray Diffraction ◽  
Lead Metaniobate ◽  
High Temperature Xrd ◽  
Pure Phase ◽  
Xrd Techniques

Orthorhombic phase of lead metaniobate (PbNb2O6) is piezoelectric with a high Curie temperature (>570°C) with high potential of wide use in important high temperature applications that cannot be covered by the popular piezoelectric materials based on BT and PZT. Difficulty of preparing it in pure phase hindered full characterisation and wide use of this long known piezoelectric material. Here,PbNb2O6 pellets have been prepared in pure orthorhombic phase and first characterised by room temperature TEM and XRD techniques, with a satisfying agreement of the two results. Next, we carried out high temperature x-ray diffraction study of its ferroelectric to paraelectric phase transition on heating across the Curie temperature, and also trace the cooling path.On heating the sample to 590°C and cooling back, there is a significant increase of cell volume.

scholarly journals Optimizing K0.5Na0.5NbO3 Single Crystal by Engineering Piezoelectric Anisotropy

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1753
Author(s):  
Weixiong Li ◽  
Chunxu Chen ◽  
Guangzhong Xie ◽  
Yuanjie Su
Keyword(s):  
Piezoelectric Coefficient ◽  
Ferroelectric Phase ◽  
Piezoelectric Properties ◽  
Piezoelectric Materials ◽  
Rhombohedral Phase ◽  
Orthorhombic Phase ◽  
Wearable Electronics ◽  
Temperature Dependent ◽  
Environmental Friendliness ◽  
Stable Temperature

K0.5Na0.5NbO3 is considered as one of the most promising lead-free piezoelectric ceramics in the field of wearable electronics because of its excellent piezoelectric properties and environmental friendliness. In this work, the temperature-dependent longitudinal piezoelectric coefficient d33* was investigated in K0.5Na0.5NbO3 single crystals via the Landau–Ginzburg–Devonshire theory. Results show that the piezoelectric anisotropy varies with the temperature and the maximum of d33max* deviates from the polar direction of the ferroelectric phase. In the tetragonal phase, d33maxt* parallels with cubic polarization direction near the tetragonal-cubic transition region, and then gradually switches toward the nonpolar direction with decreasing temperatures. The maximum of d33o* in the orthorhombic phase reveals a distinct varying trend in different crystal planes. As for the rhombohedral phase, slight fluctuation of the maximum of d33r* was observed and delivered a more stable temperature-dependent maximum d33maxr* and its corresponding angle θmax in comparison with tetragonal and orthorhombic phases. This work not only sheds some light on the temperature-dependent phase transitions, but also paves the way for the optimization of piezoelectric properties in piezoelectric materials and devices.

Effect of zirconia content on electrical conductivities of mullite/zirconia composites measured by impedance spectroscopy

2008 ◽  
Vol 23 (8) ◽  
pp. 2125-2132 ◽  
Author(s):  
Hong-Da Ko ◽  
Chien-Cheng Lin ◽  
Kuo-Chuang Chiu
Keyword(s):  
Impedance Spectroscopy ◽  
Grain Boundaries ◽  
Electrical Conduction ◽  
Activation Energies ◽  
Impedance Spectra ◽  
Ac Impedance Spectroscopy ◽  
Electrical Conductivities ◽  
Zirconia Composites ◽  
Monolithic Zirconia ◽  
Zirconia Content

Electrical conductivities of various mullite/zirconia composites, as well as monolithic mullite and zirconia, were measured using AC impedance spectroscopy from 100 Hz to 10 MHz at temperatures ranging from 150 to 1300 °C. The impedance spectra of monolithic zirconia and mullite/zirconia composites showed two semicircles because of the contributions from grains and grain boundaries, while those of monolithic mullite had one semicircle due to the predominant contribution from grains. This indicates that the conductivities of the mullite/zirconia composites increased with zirconia content. The activation energies of electrical conduction in mullite and zirconia were about 65 and 79 kJ/mol, respectively, and those of mullite/zirconia composites were between 65 and 79 kJ/mol. While the conductivities of various composites at 1 MHz were fitted by Lichtenecker’s rule, the general mixing equation could be applied to the conductivities measured at 1 kHz.

Symmetric Electrodes for Solid Fuel Cells Based on Sr-Doped LaFe0.7Ni0.3O3-δ

2017 ◽  
Vol 887 ◽  
pp. 24-31
Author(s):  
Omar Ben Mya ◽  
Mahmoud Omari ◽  
Lucia dos Santos-Gomez ◽  
David Marerro-Lopezd
Keyword(s):  
Fuel Cells ◽  
Solid Fuel ◽  
Chemical Reactivity ◽  
Orthorhombic Phase ◽  
Rietveld Analysis ◽  
Cubic Phase ◽  
Total Conductivity ◽  
Sem Images ◽  
Low Frequencies ◽  
X Ray

Perovskite La1-xSrxFe0.7Ni0.3O3-δ with x = 0.0, 0.1 &0.2 denoted LSFNx has been investigated as potential symmetrical electrode in solid fuel cells (SOFCs). The crystal structure is in pure orthorhombic phase for x = 0.0, orthorhombic-cubic phase coexist for x = 0.1 and pure cubic phase for x = 0.2. Structural properties are studied by X-ray powder diffraction (XRPD), refined by Rietveld analysis. SEM images show the morphology of as prepared and calcined samples either the compatibility between those electrodes and LSGM electrolyte in presence of 50% wt of Ce0.8Gd0.2O2-δ, so that, lower chemical reactivity was found. Total conductivity, impedance in high, medium and low frequencies HF, MF and LF respectively, and resistance polarization (Rp) are determined in air. LaFe0.7Ni0.3O3-δ has a good response in all ranges of frequencies but La0.9Sr0.1Fe0.7Ni0.3O3-δ and La0.8Sr0.2Fe0.7Ni0.3O3-δ have response only in HF and MF and exhibit Rp values as low as LaFe0.7Ni0.3O3-δ .

PEMFC impedance spectroscopy using synthetic wide-band signals

2014 ◽  
Vol 39 (8) ◽  
pp. 4005-4008 ◽  
Author(s):  
Tamara Guerrero Cervera ◽  
Alfredo P. Vega-Leal ◽  
Gloria Adame García ◽  
Javier Brey Sánchez
Keyword(s):  
Impedance Spectroscopy ◽  
Wide Band

scholarly journals Effect of Ga and Zr Substitution on the Properties of Dy2Fe17−XZrX and Dy2Fe16Ga1−xZrx (0 ≤ x ≤ 1) Intermetallic Compounds Prepared via Arc Melting Process

2020 ◽  
Vol 6 (1) ◽  
pp. 9
Author(s):  
Jiba Nath Dahal ◽  
K.S. Syed Ali ◽  
S.R. Mishra ◽  
Dipesh Neupane
Keyword(s):  
Curie Temperature ◽  
Cell Volume ◽  
Intermetallic Compounds ◽  
Unit Cell Volume ◽  
Melting Process ◽  
Rietveld Analysis ◽  
Unit Cell ◽  
Average Hyperfine Field ◽  
Crystalline System ◽  
Ga Substitution

The effects of substitution of Zr and Ga on the structural and magnetic properties of Dy2Fe17 intermetallic compound were investigated in this study. The Rietveld analysis confirmed that the crystalline system was a Th2Ni17 structure. Lattice parameters a (Å) and c (Å), unit cell volume (Å3), and bonding distance (Å) were calculated using Rietveld analysis. The unit cell volume of Dy2Fe17−xZrx and Dy2Fe16Ga1−xZrx increased linearly with Zr and Ga substitution. The Curie temperature (Tc) of Dy2Fe17−xZrx and Dy2Fe16Ga1−xZrx was found to be Zr content-dependent. The maximum Curie temperatures were observed at 510 K (x = 0.75 Zr content) for Dy2Fe17−xZrx and 505.1 K (x = 0.5 Zr content) for Dy2Fe16Ga1−xZrx, which are 102 K and 97 K higher than the value found for Dy2Fe17, respectively. The room-temperature Mössbauer analysis showed a decrease in the average hyperfine field and increases in the isomer shift with Zr doping. The overall improvement in Curie temperature with the substitution strategy of Zr–Ga substitution in 2:17 intermetallic compounds could find potential use of these magnetic compounds in high-temperature applications.

Properties of New Superionic Compounds (NH4)6LiZr4-nHfnF23 (n=1, 3)

2018 ◽  
Vol 386 ◽  
pp. 305-308
Author(s):  
Anatoly Podgorbunsky ◽  
Tamara Antokhina ◽  
Sergey V. Gnedenkov
Keyword(s):  
Phase Transitions ◽  
Charge Transfer ◽  
Ionic Conductivity ◽  
Impedance Spectroscopy ◽  
Activation Energies ◽  
High Ionic Conductivity

The phase transitions and conductivity of novel compounds (NH4)6LiZr4-nHfnF23 (n = 1, 3) were studied by DSC and impedance spectroscopy. The structure and the activation energies of the charge transfer in these compounds were estimated. The high ionic conductivity of these fluorocomplexes reaches 10-2 S/cm at 453 K.

scholarly journals Modeling Hysteresis with Inertial-Dependent Prandtl-Ishlinskii Model in Wide-Band Frequency-Operated Piezoelectric Actuator

2012 ◽  
Vol 2012 ◽  
pp. 1-15 ◽  
Author(s):  
Vahid Hassani ◽  
Tegoeh Tjahjowidodo ◽  
Albert D. Soetarto
Keyword(s):  
Piezoelectric Actuator ◽  
Piezoelectric Materials ◽  
Wide Band ◽  
Hysteretic Behavior ◽  
Nonlinear Phenomenon ◽  
Sensors And Actuators ◽  
Band Frequency ◽  
Control Framework ◽  
Stop Operator ◽  
Feed Forward Controller

One of the major problems occurring in many technical applications is the presence of the hysteretic behavior in sensors and actuators, which causes a nonlinear relationship between input and output variables in such devices. Since the nonlinear phenomenon of hysteresis degrades the performance of the piezoelectric materials and piezoelectric drive mechanisms, for example, in positioning control framework, it has to be characterized in order to mitigate the effect of the nonlinearity in the devices. This paper is aimed to characterize and model the hysteresis in typical piezoelectric actuators under load-free and preloaded circumstances incorporating the inertial effect of the system. For this purpose, the piezoelectric actuator is modeled as a mass-spring-damper system, which is expressed in terms of a stop operator as one of the essential yet efficient hysteresis operators in the Prandtl-Ishlinskii (PI) model. The reason of utilizing the stop operator in this study is for the sake of control purposes, as the stop operator plays as the inverse of the play operator in the PI model and can be used in a feed-forward controller scheme to suppress the effect of hysteresis in general control framework. The results reveal that this model exhibits better correspondence to the measurement output compared to that of the classical PI model.

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