scholarly journals The effects of additive on microstructure and electrical properties of batio3 ceramics

2004 ◽  
Vol 1 (3) ◽  
pp. 89-98 ◽  
Author(s):  
Vesna Paunovic ◽  
Ljiljana Zivkovic ◽  
Ljubomir Vracar ◽  
Vojislav Mitic ◽  
Miroslav Miljkovic
Keyword(s):  
Dielectric Constant ◽  
Curie Temperature ◽  
Room Temperature ◽  
Low Frequency ◽  
Dissipation Factor ◽  
The Other ◽  
Uniform Microstructure ◽  
Average Grain Size ◽  
Solid State Sintering ◽  
Curie Temperatures

In this paper comparative investigations of microstructure and dielectric properties of BaTiO3 ceramics doped with 1.0 wt% of Nb2O5, MnCO3 and CaZrO3 have been done. BaTiO3 samples were prepared using conventional method of solid state sintering at 13000C for two hours. Two distinguish micro structural regions can be observed in sample doped with Nb2O5. The first one, with a very small grained microstructure and the other one, with a rod like grains. In MnCO3 and CaZrO3 doped ceramics the uniform microstructure is formed with average grain size about 0.5- 2?m and 3-5?m respectively. The highest value of dielectric permittivity at room temperature and the greatest change of permittivity in function of temperature were observed in MnCO3/BaTiO3. In all investigated samples dielectric constant after initially large value at low frequency attains a constant value at f = 6kHz. A dissipation factor is independent of frequency greater than 10 kHz and, depending of systems, lies in the range from 0.035 to 0.25. At temperatures above Curie temperatures, the permittivity of all investigated samples follows a Curie- Weiss law. A slight shift of Curie temperature to the lower temperatures, in respect of Curie temperature for undoped BaTiO3, was observed in all investigated samples.

scholarly journals Enhanced dielectric properties in la modified barium titanate ceramics

2019 ◽  
Vol 32 (2) ◽  
pp. 179-193 ◽  
Author(s):  
Vesna Paunovic ◽  
Zoran Prijic ◽  
Milos Djordjevic ◽  
Vojislav Mitic
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Dielectric Properties ◽  
Curie Temperature ◽  
Room Temperature ◽  
Dissipation Factor ◽  
Dielectric Constants ◽  
Phase Transformation Temperature ◽  
Average Grain Size ◽  
La Doped

Donor/acceptor (La/Mn) doped BaTiO3 ceramics, sintered at different temperatures, were studied regarding their microstructure and dielectric properties as well as the dielectric response in a ferroelectric/paraelectric regime. The concentrations of La3+ as donor, ranging from 0.1 to 5.0 at% were used for doping, while a content of Mn4+ as acceptor was at 0.05 at% in all samples. The sintering temperature of codoped samples were 1290? and 1350?C. A reduction in grain size and fine-grained microstructure with average grain size from 0.5 to 2.0 mm was observed in low doped samples, whereas the abnormal growth of individual grains took place in the 2 at% and 5 at% La doped specimens. The dielectric properties of these samples were investigated as a function of frequency (100Hz - 20 kHz) and temperature (20-180?C). The measured results suggested that both the dielectric constants of the ceramics (er at room temperature and ermax at the Curie temperature) decreased as the concentration of La3+ increased. The dielectric permittivity was in the range of 944 to 3200. For samples doped with 0.1 at% La and sintered at 1350?C, the highest dielectric constant value at room temperature (er= 3200) and Curie temperature (er= 5000) were measured. For all measured samples the dissipation factor was less than 0.09. With an increase in La contents, dielectric measurements exhibited shift in the Curie temperature (Tc) towards the low temperature. Using the Curie-Weiss and the modified Curie-Weiss law, Curie's constant C was calculated as well as the parameterg, which describes the deviation from the linear dependence er of T above the phase transformation temperature. The calculated values for g ranged from 1.01 to 1.43. These values indicate a sharp phase transformation in lowdoped and diffuse phase transformation in highly La doped samples. The phase transition was reflected in the values of C that started to decrease with increasing dopant content.

Pyroelectric Properties of the Plt(10) Thin Film on the P-Doped Poly Silicon

1996 ◽  
Vol 433 ◽  
Author(s):  
Seong Jun Kang ◽  
Yung Sup Yoon ◽  
Dong Il Kim
Keyword(s):  
Thin Film ◽  
Dielectric Constant ◽  
Curie Temperature ◽  
Room Temperature ◽  
Sol Gel ◽  
Pyroelectric Coefficient ◽  
Pyroelectric Properties ◽  
Gel Method ◽  
Sol Gel Method ◽  
Poly Silicon

AbstractWe have studied the pyroelectric properties of the PLT(10) thin film deposited on a p-doped poly-Si electrode by using the sol-gel method. Measurement of the dielectric constant as a function of temperature shows the typical characteristics of a ferroelectric. The dielectric constant reaches a maximum at 295°C, which can be thought of as the Curie temperature. The PLT(10) thin film on p-doped poly-Si fabricated in this research shows excellent pyroelectric properties. The pyroelectric coefficient and the fiqures of merit, Fv and FD at room temperature are measured as 5.76 × 10−8 C/cm2 °C, 1.17 × 10−10C-cm/J and 0.93 × 10−8C-cm/J, respectively.

The Role of Niobium in (Ca, Si, Ce, Nb)-Doped TiO2 Varistors

2007 ◽  
Vol 280-283 ◽  
pp. 297-300 ◽  
Author(s):  
Shao Hua Luo ◽  
Zi Long Tang ◽  
Hong Yun Li ◽  
Zhong Tai Zhang ◽  
Xi Zhou Xiong
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Room Temperature ◽  
Structural Characteristics ◽  
Nonlinear Coefficient ◽  
The Other ◽  
Optimal Composition ◽  
Low Loss ◽  
Nb Addition

The present work attempted to investigate the effect of Nb addition on the electrical properties of the (Ca,Si,Ce,Nb)-doped TiO2 ceramics. The content of added niobium is in the range 0.1-1.0mol %, while that of the other additives keeps constant. The results showed that an optimal composition doped with 0.8mol% Nb2O5, followed by sintering at 1350°C, was obtained with low V1 mA of 7.22V, high nonlinear coefficient of 5.76, ultrahigh dielectric constant (er = 86000) as well as relatively low loss (tgd = 0.52) in room temperature at 1 kHz. SEM studies show that change of niobium had significant influence on grain growth and micro structural characteristics of the sintered samples.

Glass-Coated Cu-Mn-Ga Microwires Produced by Taylor-Ulitovsky Technique

2009 ◽  
Vol 152-153 ◽  
pp. 79-84 ◽  
Author(s):  
Joan Josep Suñol ◽  
L. Escoda ◽  
C. García ◽  
V.M. Prida ◽  
Victor Vega ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solid Solution ◽  
Curie Temperature ◽  
Energy Dispersive Spectroscopy ◽  
Room Temperature ◽  
Alloy Composition ◽  
The Other ◽  
X Ray Diffraction ◽  
X Ray ◽  
Low Magnetic Field

Glass-coated Cu-Mn-Ga microwires were fabricated by Taylor-Ulitovsky technique. By means of energy dispersive spectroscopy microanalysis, an average alloy composition of Cu56Ga28Mn16 was determined. The temperature dependence of magnetization measured at a low magnetic field showed the coexistence of two ferromagnetic phases. The Curie temperature of one phase is 125 K and above room temperature for the other one. X-ray diffraction at room temperature and at 100 K reflects the presence of the same three crystalline phases corresponding to the cubic B2 Cu-Mn-Ga structure as a main phase and the minor phases of fcc Cu rich solid solution with Mn and Ga and the monoclinic CuO.

scholarly journals Huge values of room-temperature dielectric constants in pellets of poly(3-methylthiophene)

2004 ◽  
Vol 19 (7) ◽  
pp. 2068-2071
Author(s):  
S. Moraes ◽  
L. Walmsley ◽  
E.C. Pereira ◽  
A.A. Correa
Keyword(s):  
Dielectric Constant ◽  
Charge Density Wave ◽  
Room Temperature ◽  
Density Wave ◽  
Low Frequency ◽  
Temperature Data ◽  
Dielectric Constants ◽  
Wave Characteristic ◽  
Rc Circuit ◽  
A Charge

Room temperature data of impedance and phase angle in pellets of electrochemically synthesized ClO4− doped poly(3-methylthiophene) (P3MT) were analyzed assuming the sample being represented by a parallel resistor-capacitor (RC) circuit or by a series RC circuit. The last assumption proved to be the correct one, and to confirm it we use the sample as the RC component of a resistor-capacitor-inductor series resonator. We discuss the possibility of this RC series behavior to be due to a charge-density wave characteristic also evidenced from the huge values of the low-frequency dielectric constant of the system.

Morphology and Curie Temperature Changes upon Annealing of Co/W(110)

1997 ◽  
Vol 475 ◽  
Author(s):  
A. Bauer ◽  
A. Mühlig ◽  
T. Günther ◽  
M. Farle ◽  
K. Baberschke ◽  
...  
Keyword(s):  
Curie Temperature ◽  
Ultrathin Films ◽  
Kerr Effect ◽  
Room Temperature ◽  
The Other ◽  
Scanning Tunneling ◽  
Optical Kerr Effect ◽  
Tunneling Microscopy ◽  
Temperature Changes ◽  
Magneto Optical Kerr Effect

ABSTRACTAnnealing of CoAV(110) ultrathin films causes rather strong changes of film morphology and magnetic properties, which has been studied by scanning tunneling microscopy (STM) and alternating-current magneto-optical Kerr effect (ac-MOKE). Annealing above 500 K of room-temperature grown 2 monolayers (ML) thick Co/W(110) films leads to the formation of islands and a decrease of the Curie temperature 7C. At 4 ML, on the other hand, a network of interconnected islands is formed upon annealing, resulting in an enhanced TC. While the increase of TC at 4 ML is explained by an increase of the local film thickness, the anomalous TC behavior at 2 ML is assigned to the occurrence of superparamagnetism.

The Magnetic Entropy Changes in Gd1-xCrx Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 2267-2270 ◽  
Author(s):  
Song Ling Huang ◽  
Dun Hui Wang ◽  
Zhi Da Han ◽  
S.K. Ren ◽  
Zheng Hua Su ◽  
...  
Keyword(s):  
Curie Temperature ◽  
Room Temperature ◽  
Magnetic Refrigeration ◽  
Magnetic Entropy ◽  
Entropy Changes ◽  
Arc Melting ◽  
Magnetic Refrigerant ◽  
Room Temperature Magnetic Refrigeration ◽  
High Level ◽  
Curie Temperatures

A series of Gd1-xCrx (x=0.01,0.03,0.05 and 0.07) alloys have been prepared by arc melting. After introducing a small quantity of Cr into Gd, the Curie temperatures of these alloys increase. Magnetic entropy changes at the Curie temperature of Gd1-xCrx (x=0.01, 0.03, 0.05) alloys are nearly the same as that of Gd. However, compared with Gd, the magnetic entropy changes of Gd1-xCrx (x=0.01, 0.03, 0.05) alloys remain at a high level in a wider temperature range. So Gd1-xCrx (x=0.01, 0.03, 0.05) alloys are more suitable as magnetic refrigerant to be used in Ericsson Recycle for room temperature magnetic refrigeration. Our results and the fact that Cr is quite cheaper than Gd, suggest that Gd1-xCrx alloys maybe utilized as refrigerant in room temperature magnetic refrigeration.

Magnetic properties of (NixCu1−x)2MnSn

1977 ◽  
Vol 55 (17) ◽  
pp. 1481-1484 ◽  
Author(s):  
R. A. MacDonald ◽  
C. V. Stager
Keyword(s):  
Magnetic Properties ◽  
Curie Temperature ◽  
Heusler Alloy ◽  
Room Temperature ◽  
Manganese Atom ◽  
Lattice Parameter ◽  
Alloy Series ◽  
Saturation Moment ◽  
Curie Temperatures

Magnetization and crystallographic measurements are reported for the Heusler alloy series (NixCu1−x)2MnSn. With the exception of Cu2MnSn and perhaps (Ni0.1Cu0.9)2MnSn all of the samples prepared had the cubic Heusler L21 structure at room temperature. The lattice parameter varies linearly as a function of composition. The saturation moment is constant at approximately 4μβ per manganese atom throughout the series. Curie temperatures vary smoothly but non-linearly with composition, providing some evidence for at least two competing mechanisms in the determination of the Curie temperature.

Electrodynamic Properties of Single-Crystal and Thin-Film Strontium Titanate, and Thin-Film Barium Strontium Titanate

1999 ◽  
Vol 603 ◽  
Author(s):  
A.T. Findikoglu ◽  
Q.X. Jia ◽  
C. Kwon ◽  
B.J. Gibbons ◽  
K.Ø. Rasmussen ◽  
...  
Keyword(s):  
Thin Film ◽  
Single Crystal ◽  
Strontium Titanate ◽  
Barium Strontium Titanate ◽  
Room Temperature ◽  
Coplanar Waveguide ◽  
Low Frequency ◽  
Dissipation Factor ◽  
Barium Strontium ◽  
Dc Bias

AbstractWe have used a coplanar waveguide structure to study broadband electrodynamic properties of single-crystal and thin-film strontium titanate (STO), and thin-film barium strontium titanate (BSTO). We have implemented low-frequency capacitance (100 Hz - 1 MHz), swept-frequency transmittance (45 MHz - 4 GHz), and time-domain transmittance (dc - several GHz) measurements to determine effective refractive index (or, dielectric constant), and dissipation factor (or, loss tangent) as a function of dc bias (up to 4×106 V/m) and temperature (20 - 300 K). The STO samples used superconducting electrodes and were designed to operate at cryogenic temperatures, whereas BSTO samples used normal conducting electrodes and exhibited optimal performance around room temperature. By using nearly identical electrode geometries for all devices, we were able to conduct a direct comparative study among them, and investigate not only single-crystal vs thin-film, but also cryogenic vs room-temperature applications.

Room Temperature Dielectric Characteristics of Chitosan-Graphene Films Embedded In Cellulose Fabric

MRS Advances ◽  
2018 ◽  
Vol 3 (1-2) ◽  
pp. 85-90
Author(s):  
Radha Perumal Ramasamy ◽  
Swathi Somanathan ◽  
Vinod K. Aswal ◽  
Miriam H. Rafailovich
Keyword(s):  
Dielectric Constant ◽  
Room Temperature ◽  
Heat Dissipation ◽  
Chitosan Film ◽  
Chitosan Solution ◽  
Dissipation Factor ◽  
Solid Polymer Electrolytes ◽  
Solid Polymer ◽  
Cellulose Fabric ◽  
Chitosan Powder

ABSTRACTDevelopment of solid polymer electrolytes has potential applications for battery technology. Membranes should be environment friendly and also have high conductivity. We use chitosan, cellulose and graphene in this research. In this work, 1% (w/v) of chitosan powder and 1.5% (w/v) of acetic acid were dissolved in double distilled water. The solution was heated to 60°C under constant stirring until the chitosan powder was completely dissolved and a semi-transparent thick chitosan solution was obtained. To this chitosan solution, appropriate amounts of graphene (grade H5-XG Sciences) was added to have 5, 10, 20 and 30% graphene (weight with respect to chitosan). The solution was sonicated for dispersing graphene and then 100ml of it was poured on plastic dishes with and without cellulose fabric in it. The films were dried by slow evaporation technique. The sample thickness varied from 200 to 300µm. SEM images showed that chitosan film formed on cellulose and had grid like structures. Chitosan deposited more on the fibres of the cellulose. This is attributed to the rectangle shaped micro pores of cellulose fabric. From the cross section of the films, it was observed that graphene arranged in stacks along the plane of the cellulose fabric and the fabric became darker as graphene concentration increased. The dielectric properties such as dielectric constant, impedance, conductivity and dissipation factor were measured from 102 - 106 Hz. The conductivity of the sample increased as the frequency increased. The conductivity of the samples at room temperature increased with increase in graphene concentrations. The conductivity varied from 10-8 to 10-5 S/Cm as the graphene concentration increases from 0 to 30%. Hence conductivity increases significantly as graphene concentration increases. From the dissipation factor for the films, the relaxation process could be observed in the frequency ranging from 102 to 105 Hz. It is observed that as frequency increases, the relaxation tend to shift towards higher frequency indicating that graphene affects the relaxation of the polymer nanocomposite. At high frequency (106Hz) dissipation factor for cellulose fabric, chitosan in cellulose, chitosan with 5% graphene in cellulose, chitosan with 10% graphene in cellulose, chitosan with 20% graphene in cellulose, chitosan with 30% graphene in cellulose are 0.14, 0.19, 0.4, 0.8 and 1.38 respectively. This shows that dissipation factor increases as the graphene concentration increases. This implies that graphene improves heat dissipation in these films. The dielectric constant was observed to be maximum for chitosan with 30% graphene in cellulose indicating that the graphene may assemble into percolation networks at higher concentrations of graphene (20 and 30%).

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