scholarly journals The Study of Dielectric Behavior and Phase Transition of Mixed Compound of Lead Tantalate Sintered with Silver Oxide with Temperature Variation

2021 ◽  
Vol 04 (06) ◽  
Author(s):  
Shri Prakash Dubey ◽  
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Temperature Variation ◽  
Smart Materials ◽  
Silver Oxide ◽  
Dielectric Behavior ◽  
Heating Cycle ◽  
Cooling Cycle ◽  
Bridge Model ◽  
Mixed Compound

The dielectric constant of mixed compound of Lead Tantalate(PbTa2O6) sintered with Silver oxide has been measured between the temperatures 40°C to 300°C using the capacitance bridge model ZENITH M 92A at the frequency of 1000 Hz. During the measurement, it is found that the properly annealed sample have three peaks at the temperature 90°C (ε = 1000), 220°C (ε =800) and 230°C (ε = 623) respectively and a high peak at the temperature of 130°C (ε = 1600) in the heating cycle curve with some intermediate fluctuations. When the variation of dielectric constant was studied in cooling cycle the peak was observed at 240ºC, above and below this temperature, dielectric constant decreases with some intermediate fluctuations showing shows a first order phase transition. The variation in heating cycle is explained on the basis of activated polarization process. When the behavior of compound is studied in cooling cycle, then pronounced hysteresis is found with certain intermediate fluctuations. The cooling cycle curve does not follow heating curve because of the temperature relaxation of the compound. The occurrence of peak at the Curie temperature is explained by the latent heat type properties of the mixed compound. The temperature variation of the mixed compound suggests for its valuable applications as active and smart materials and its applications in the ceramics.

scholarly journals Ferroelectric Aspect and Phase Transitions of Solid Solution of Cadmium Acetate with Aluminium (III) Oxide

2021 ◽  
Vol 04 (08) ◽  
Author(s):  
Shri Prakash Dubey ◽  
Keyword(s):  
Solid Solution ◽  
Dielectric Constant ◽  
Resonant Frequency ◽  
Quality Factor ◽  
Aluminium Oxide ◽  
Cadmium Acetate ◽  
Effect Of Temperature ◽  
Oxide Content ◽  
Cooling Cycle ◽  
Bridge Model

The behavior of variation of dielectric constant with temperature of solid solution of Cadmium Acetate Cd(C2H3O2)2 with Aluminium (III) Oxide Al2O3 and other dielectric parameters have been measured between the temperatures 35°C to 100°C using the capacitance bridge model ZENITH-FM89A and Q meter at the frequency of 2000 Hz. In the measurement, it have been observed that the compound has lower value of dielectric constant (ε = 1580) below 36ºC, which rises upto a value of 5600 at the moderate temperature of 45ºC. After this temperature, the dielectric constant of compound decreases upto the value of nearly 3521 at the temperature of 75ºC and a high peak at the temperature of 76°C (ε = 7000) in the heating cycle curve with some fluctuations.. When the variation of dielectric constant was studied in cooling cycle the peak was observed at 62ºC(ε = 6500), above and below this temperature dielectric constant decreases with some intermediate fluctuations and by increasing aluminium oxide content in the mother compound, its quality factor also increases with a little effect on dielectric constant. The cooling cycle curve does not follow heating curve because of the relaxor behaviour of the compound. The results have been explained on the basis of crystal structure changes and the possibility of free internal rotation of acetate groups within the crystal lattice at elevated temperature. One of the advantages of Cd(C2H3O2)2 with Al2O3 is that by varying the Aluminium Oxide content, one can control temperature coefficient of resonant frequency τf without affecting the other properties. This is important for many ferroelectric applications because τf of near about low value is not always required. A non-zero τf is often preferable to compensate for frequency variation due to the effect of temperature change on the resonator housing and dielectric support structure. Solid solution of Cadmium Acetate with Aluminium Oxide suggests for its valuable applications as dielectric material with excellent properties useful in ceramics engineering and communication system. KEY WORDS: Polarization, Quality Factor, Dielectric Constant, Phase Transition, Curie temperature, Resonant Frequency and Ceramics Engineering.

Evidence for Antiferroelectric Behavior in KNbO3/KTaO3 Superlattices

2002 ◽  
Vol 720 ◽  
Author(s):  
J. Sigman ◽  
H. M. Christen ◽  
P. H. Fleming ◽  
L. A. Boatner ◽  
D. P. Norton
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Temperature Region ◽  
Dielectric Response ◽  
Nonlinear Response ◽  
Structural Phase ◽  
Dielectric Behavior ◽  
Ferroelectric Materials ◽  
Dc Bias ◽  
Superlattice Structures

AbstractThe dielectric response in artificially layered 1x1 KTaO3/KNbO3 perovskite superlattice structures is reported. While KTaO3 and KNbO3 are ferroelectric or paraelectric, respectively, superlattices appear antiferroelectric based on an increase in dielectric constant with applied dc bias. This “positive tunability” in dielectric response occurs at the same temperature region where a structural phase transition is observed. This dielectric behavior is inconsistent with the nonlinear response for either paraelectric or ferroelectric materials. However, an increase in the dielectric constant with applied electric field is consistent with antiferroelectric behavior. The antiferroelectric ordering correlates with cation modulation imposed by the superlattice.

The High DC Electric Field Effects on the Dielectric Behavior of Barium Strontium Titanate Ceramics

2013 ◽  
Vol 547 ◽  
pp. 125-132
Author(s):  
Qi Wei Zhang ◽  
Ji Wei Zhai ◽  
Xi Yao
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Electric Field ◽  
Paraelectric Phase ◽  
Dielectric Behavior ◽  
Solid State Reactions ◽  
Electric Field Effects ◽  
Temperature Dependences ◽  
Dc Electric Field ◽  
Titanate Ceramics

BaxSr1-xTiO3 (x=0.4, 0.5, 0.6) ceramics were fabricated by the conventional solid-state reactions method. The temperature dependences of the dielectric constant and tunability were investigated under high DC electric field. It was found that the change of dielectric constant and tunability under the applied electric field were closely related to ferroelectric phase, phase transition region and paraelectric phase states. The Curie temperature (Tc) was gradually shifted to higher temperature and were broadened and depressed with increasing of DC electric field. The tunability dependence of temperature exhibits different trends in a wide temperature range and reaches a maximum value near the ferroelectric-paraelectric phase transition. These results may be helpful in understanding the mechanism of dielectric response under higher electric field.

Influence of Ca-Doping on Structural, Magnetic and Dielectric Properties of Ba3Co2-xCaxFe24O41 Hexaferrite Powders

2015 ◽  
Vol 241 ◽  
pp. 226-236 ◽  
Author(s):  
Neha Solanki ◽  
Rajshree B. Jotania
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Sol Gel ◽  
Calcium Content ◽  
Combustion Method ◽  
Dielectric Behavior ◽  
Dielectric Parameters ◽  
Ca Doping ◽  
Auto Combustion ◽  
Magnetic And Dielectric Properties

Influence of Ca substitution on structural, magnetic and dielectric properties of Ba3Co2-xCaxFe24O41(where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), prepared by Sol-Gel auto-combustion method, has been investigated in present studies. The obtained powder was sintered at 950 oC for 4 hrs. in the static air atmosphere. Structural analysis of Ca-doped Ba3Co2-xCaxFe24O41powders revealed pure Z-type hexaferrite phase at low temperature. The frequency dependent dielectric constant (Єʹ) and magnetic properties such as remanent magnetization (Mr), saturation magnetization (Ms) and coercivity (Hc) were studied. It is observed that coercivity increased gradually with increase in calcium content. The real dielectric constant (Єʹ) and dielectric loss tangent (tan δ) were studied in the frequency range of 20Hz to 2MHz. The dielectric parameters for all samples show normal dielectric behavior as observed in hexaferrites. Contents of Paper

COMPARATIVE STUDY OF DIELECTRIC BEHAVIOR OF Mn0.4Zn0.6Fe2O4 NANOFERRITE BY CITRATE PRECURSOR METHOD

2008 ◽  
Vol 22 (16) ◽  
pp. 2537-2544 ◽  
Author(s):  
PREETI MATHUR ◽  
ATUL THAKUR ◽  
M. SINGH
Keyword(s):  
Particle Size ◽  
Dielectric Constant ◽  
Comparative Study ◽  
Average Particle Size ◽  
Dielectric Behavior ◽  
Average Particle ◽  
Oxidizing Agent ◽  
Precursor Method ◽  
Citrate Precursor ◽  
Citrate Precursor Method

In the present work, comparative study of the dielectric behavior of Mn 0.4 Zn 0.6 Fe 2 O 4 ferrite synthesized with and without H 2 O 2 (hydrogen peroxide) has been presented. The dc resistivity has been improved by the citrate precursor method as compared to the ceramic method, and it is further improved by the addition of H 2 O 2, which acts as a strong oxidizing agent. We have shown by means of X-ray diffraction that the resulting ferrite is made up of nanocrystallites and the average size of these nanocrystallites–calculated by Scherrer's formula–depends on the polarizer. The average particle size was found to be ~70 nm with H 2 O 2 and ~88 nm without H 2 O 2. The particle size is further confirmed by scanning electron microscopy. Both the results are found to be in good agreement. The decrease in dielectric constant and dielectric loss factor by addition of oxidizing agent is justified by inverse proportionality between the resistivity and dielectric constant. Possible mechanisms contributing to these processes have been discussed.

Ferroelastic Phase Transition and Switchable Dielectric Constant in Heterometallic Niccolite Formate Frameworks

2017 ◽  
Vol 57 (2) ◽  
pp. 537-540 ◽  
Author(s):  
Kai Wang ◽  
Jian-Bo Xiong ◽  
Bin Xia ◽  
Qing-Lun Wang ◽  
Yu-Zhang Tong ◽  
...  
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Ferroelastic Phase Transition

ON THE DIELECTRIC BEHAVIOR OF LiCo3/5Fe2/5VO4 CERAMICS

2010 ◽  
Vol 24 (07) ◽  
pp. 665-670
Author(s):  
MOTI RAM
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Frequency Dependence ◽  
Chemical Method ◽  
Arrhenius Plot ◽  
Dielectric Behavior ◽  
Tangent Loss ◽  
Low Frequencies ◽  
Different Temperatures ◽  
Tan Δ

The LiCo 3/5 Fe 2/5 VO 4 ceramics has been fabricated by solution-based chemical method. Frequency dependence of the dielectric constant (εr) at different temperatures exhibits a dispersive behavior at low frequencies. Temperature dependence of εr at different frequencies indicates the dielectric anomalies in εr at Tc (transition temperature) = 190°C, 223°C, 263°C and 283°C with (εr) max ~ 5370, 1976, 690 and 429 for 1, 10, 50 and 100 kHz, respectively. Frequency dependence of tangent loss ( tan δ) at different temperatures indicates the presence of dielectric relaxation in the material. The value of activation energy estimated from the Arrhenius plot of log (τd) with 103/T is ~(0.396 ± 0.012) eV.

scholarly journals Поведение керамических твердых растворов 33PbYb-=SUB=-1/2-=/SUB=-Nb-=SUB=-1/2-=/SUB=-O-=SUB=-3-=/SUB=--22PbZrO-=SUB=-3-=/SUB=--45PbTiO-=SUB=-3-=/SUB=- в электрическом поле

2020 ◽  
Vol 46 (6) ◽  
pp. 31
Author(s):  
Л.С. Камзина ◽  
G. Li
Keyword(s):  
Phase Transition ◽  
Dielectric Constant ◽  
Electric Field ◽  
Electric Fields ◽  
Dielectric Parameters ◽  
Morphotropic Phase Transition ◽  
Temperature Dependences ◽  
Pseudocubic Phase

The temperature dependences of the dielectric parameters were studied, as well as the changes in the dielectric constant with time in ceramic 33PbYb1 / 2Nb1 / 2O3-22PbZrO3-45 PbTiO3 samples in electric fields (0 <E <8 kV / cm). It is shown that in the phase existing below the temperature of the morphotropic phase transition, in addition to the rhombohedral and tetragonal phases, a small fraction of the relaxor pseudocubic phase is present. It was found that, unlike other relaxors, the dielectric constant practically does not change with time when an electric field is applied in the phase below the temperature of the morphotropic phase transition. Possible reasons for this behavior are discussed.

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