Dielectric Properties and Microstructure of BaTiO3 Ceramics

2002 ◽  
Vol 718 ◽  
Author(s):  
Dae-Chul Park ◽  
Jun-ichi Itoh ◽  
Isao Sakaguchi ◽  
Naoki Ohashi ◽  
Toyohiko Yano ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Curie Temperature ◽  
Secondary Phase ◽  
Dielectric Constants ◽  
Core Shell ◽  
Temperature Range ◽  
The Core ◽  
La Doped ◽  
Mg Doped

AbstractDielectric properties and microstructure were investigated in BaTiO3 ceramics with various additives, Ho2O3, MgO, Ho2O3/MgO, and La2O3. The dielectric constants were increased up to ∼4000 and ∼3000 at 25°C in the 1 mol% Ho-doped and 0.5 mol% Mg-doped BaTiO3 materials, respectively. The BaTiO3 material codoped with 3 mol% Ho + 1.5 mol% Mg led to increase dielectric constant up to ∼6000 at 25°C and the dielectric constant peak around Curie temperature was suppressed at temperature range of from 25°C to 125°C. The size of BaTiO3 grains depended on the content and kind of an additive. Core-shell grains and secondary phase were also dependent on an additive. Core-shell grains were formed completely in Ho-doped BaTiO3 except for 0.5 mol%, but the structure was little observed in Mg- and La-doped BaTiO3 material. Codoped BaTiO3 also formed the core-shell grains.

Epitaxial Growth and Anisotropic Dielectric Properties of La-Doped Bi4Ti3O12 Thin Films

2007 ◽  
Vol 124-126 ◽  
pp. 177-180
Author(s):  
Jang Sik Lee ◽  
Q.X. Jia
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Bottom Electrode ◽  
Dielectric Constants ◽  
The Other ◽  
Field Range ◽  
Anisotropic Dielectric ◽  
Dielectric Nonlinearity ◽  
La Doped

To investigate the anisotropic dielectric properties of layer-structured bismuth-based ferroelectrics along different crystal directions, we fabricate devices along different crystal orientations using highly c-axis oriented Bi3.25La0.75Ti3O12 (BLT) thin films on (001) LaAlO3 (LAO) substrates. Experimental results have shown that the dielectric properties of the BLT films are highly anisotropic along different crystal directions. The dielectric constants (1MHz at 300 K) are 358 and 160 along [100] and [110], respectively. Dielectric nonlinearity is also detected along these crystal directions. On the other hand, a much smaller dielectric constant and no detectable dielectric nonlinearity in a field range of 0-200 kV/cm are observed for films along [001] when c-axis oriented SRO is used as the bottom electrode.

Dielectric Properties of (Bi1/2Na1/2)TiO3-SrTiO3 Ferroelectric Ceramics

2007 ◽  
Vol 336-338 ◽  
pp. 49-50
Author(s):  
Chao Liu ◽  
Yuan Fang Qu ◽  
Feng Long Han ◽  
Yuan Liang Li ◽  
Xiao Yan Li
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Curie Temperature ◽  
Ferroelectric Properties ◽  
Dielectric Constants ◽  
Ferroelectric Ceramics

Ferroelectric properties of (Bi1/2Na1/2) TiO3-SrTiO3 were studied. The dielectric properties were measured at 1KHz. It was found that the dielectric constants are improved with the increase of additive amount of BNT. If the amount continues increasing, the properties become worse, the optimum dielectric constant of the samples can reach 4300. When the proportion of (Bi1/2Na1/2)TiO3: SrTiO3 is 65:35, with the increase of additive amount of MnCO3, the Curie temperature descends obviously. The dielectric constant increased at beginning and dropped sharply when the amount of MnCO3 exceeds 1.1wt%.

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.

Tuning the mechanical and dielectric properties of zinc incorporated hydroxyapatite

2020 ◽  
Vol 16 ◽  
Author(s):  
Alliya Qamar ◽  
Rehana Zia ◽  
Madeeha Riaz
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Bone Growth ◽  
Healing Process ◽  
Secondary Phase ◽  
Chemical Precipitation ◽  
Hexagonal Structure ◽  
Precipitation Method ◽  
Low Frequencies ◽  
A Minor

Background: Hydroxyapatite is similar to bone mineral in chemical composition, has good biocompatibility with host tissue and bone. Objective: This work aims to tailor the mechanical and dielectric properties of hydroxyapatite with zinc sudstitution, to improve wearability of implant and accelerate the healing process. Method: Pure and zinc incorporated hydroxyapatite Ca10(PO4)6(OH)2 samples have been successfully prepared by means of the chemical precipitation method. Results: The results showed that hydroxyapatite(Hap) having hexagonal structure was the major phase identified in all the samples. It was found that secondary phase of β-tricalcium phosphate (β-TCP) formed due to addition of Zinc resulting in biphasic structure BCP (Hap + β-TCP). A minor phase of ZnO also formed for higher concentration of Zn (Zn ≥ 2mol%) doping. It was found that the Zn incorporation to Hap enhanced both mechanical and dielectric properties without altering the bioactive properties. The microhardness increased upto 0.87 GPa for Zn concentration equal to 1.5mol%, which is comparable to the human bone ~0.3 - 0.9 GPa. The dielectric properties evaluated in the study showed that 1.5 mol% Zn doped hydroxyapatite had highest dielectric constant. Higher values of dielectric constant at low frequencies signifies its importance in healing processes and bone growth due to polarization of the material under the influence of electric field. Conclusion: Sample Z1.5 having 1.5 mol% Zn doping showed the most optimized properties suitable for bone regeneration applications.

Pulsed Laser Deposition of BaxSr1−xTiO3 Films on MgO, LaAlO3 and SrTiO3 for Tunable Microwave Applications

1998 ◽  
Vol 541 ◽  
Author(s):  
Wontae Chang ◽  
James S. Horwitz ◽  
Won-Jeong Kim ◽  
Jeffrey M. Pond ◽  
Steven W. Kirchoefer ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Electric Field ◽  
Pulsed Laser Deposition ◽  
Pulsed Laser ◽  
Dielectric Constants ◽  
Laser Deposition ◽  
Film Stress ◽  
Donor Acceptor ◽  
Bst Films

AbstractSingle phase BaxSr1−xTiO3 (BST) films (∼0.5-7 μm thick) have been deposited onto single crystal substrates (MgO, LaAlO3, SrTiO3) by pulsed laser deposition. Silver interdigitated electrodes were deposited on top of the ferroelectric film. The room temperature capacitance and dielectric Q (1/tanδ) of the film have been measured as a function of electric field (≤80 kV/cm) at 1 - 20 GHz. The dielectric properties of the film are observed to strongly depend on substrate type and post-deposition processing. After annealing (≤1000° C), it was observed that the dielectric constant and % tuning decreased and the dielectric Q increased for films deposited onto MgO, and the opposite effect was observed for films deposited onto LaA1O3. Presumably, this change in dielectric properties is due to the changes in film stress. Very thin (∼50 Å) amorphous BST films were successfully used as a stress-relief layer for the subsequently deposited crystalline BST (∼5000 Å) films to maximize % tuning and dielectric Q. Films have been deposited from stoichiometric targets and targets that have excess Ba and Sr. The additional Ba and Sr has been added to the target to compensate for deficiencies in Ba and Sr observed in the deposited BST (x=0.5) films. Films deposited from compensated targets have higher dielectric constants than films deposited from stoichiometric targets. Donor/acceptor dopants have also been added to the BST target (Mn, W, Fe ≤4 mol.%) to further improve the dielectric properties. The relationship between the dielectric constant, the dielectric Q, the change in dielectric constant with electric field is discussed.

Enhanced dielectric properties of conductive-dielectric composites by reducing particle size and core@shell method

2018 ◽  
Vol 11 (01) ◽  
pp. 1850010 ◽  
Author(s):  
Yuqiang Guo ◽  
Yifei Wang ◽  
Yaxuan Ren ◽  
Mingzhu Fu ◽  
Hongmei Ma ◽  
...  
Keyword(s):  
Particle Size ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Mass Fraction ◽  
Core Shell ◽  
Particle Sizes ◽  
Conductive Particle ◽  
Threshold Theory ◽  
Conductive Polyaniline

Based on the percolation threshold theory of conductive-dielectric composites, the dielectric constant can be improved more by adding a certain mass fraction of conductive particle into polymer matrix. However, the dielectric loss increases with the increasing mass fraction of conductive particle. In this paper, conductive Polyaniline (PANI) with different particle sizes is utilized to illustrate that reducing particle size can improve the dielectric properties. The dielectric constant is increased from 319 to 540, and dielectric loss is decreased from 2.34 to 0.85 when PANI with smaller particle size is used. Moreover, PANI coated with an insulating surfactant layer can further improve the dielectric properties, the experimental results show that the dielectric constant of the composite could be more than 1000, while the dielectric loss is 0.35 at 1[Formula: see text]KHz.

Synthesis and Characteristics of MgO Coated BST-Mg2TiO4 Composite Ceramics

2012 ◽  
Vol 512-515 ◽  
pp. 1180-1183
Author(s):  
Qian Qian Jia ◽  
Hui Ming Ji ◽  
Shan Liu ◽  
Xiao Lei Li ◽  
Zheng Guo Jin
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Curie Temperature ◽  
Loss Tangent ◽  
Phase Shifters ◽  
Precipitation Method ◽  
Composite Ceramics ◽  
Low Dielectric ◽  
Dielectric Constant And Loss ◽  
Bst Ceramics

The (Ba, Sr)TiO3 (hereafter BST) ceramics are promising candidate for applying in tunable devices. MgO coated BST-Mg2TiO4 (BSTM-MT) composite ceramics were prepared to obtain the low dielectric constant, low dielectric loss, good dielectric constant temperature stability, and high tunability of BST ceramics. The Ba0.55Sr0.40Ca0.05TiO3 nanoparticles were coated with MgO using the precipitation method and then mixed with Mg2TiO4 powders to fabricate BSTM-MT composite ceramics. The morphologies, phases, elements, and dielectric properties of the sintered ceramics were investigated. The core-shell structure of BST powder wrapped with MgO was clearly observed from the TEM image. After sintered at 1100 °C for 2 h, the composite ceramics expressed dense microstructures from SEM images and two main phases BST and Mg2TiO4 were detected in the XRD patterns. The dielectric constant and loss tangent were both reduced after the coating. The reduced dielectric constant and loss tangent of BSTM-MT were 190, 0.0011 (2MHz), respectively. The ceramics exhibited the diffuse phase transition near the Curie temperature and the Curie temperature shifted from 10 °C to 5 °C after the coating. Since the continuous Ti-O bonds were disconnected with the MgO coating, the tunability was reduced to 15.14 % under a DC bias field of 1.1 kV/mm. The optimistic dielectric properties made it useful for the application of tunable capacitors and phase shifters.

Structural and dielectric properties of Bi2NbxVi−xO5.5 ceramics

1996 ◽  
Vol 11 (9) ◽  
pp. 2288-2292 ◽  
Author(s):  
K. B. R. Varma ◽  
K. V. R. Prasad
Keyword(s):  
Differential Scanning Calorimetry ◽  
Grain Size ◽  
Dielectric Properties ◽  
Curie Temperature ◽  
Room Temperature ◽  
Dielectric Constants ◽  
Scanning Calorimetry ◽  
Electron Microscopic ◽  
Scanning Electron Microscopic ◽  
Scanning Electron

Bi2Nbx V1−xO5.5 ceramics with x ranging from 0.01 to 0.5 have been prepared. The crystal system transforms from an orthorhombic to tetragonal at x 3= 0.1 and it persists until x = 0.5. Scanning electron microscopic (SEM) investigations carried out on thermally etched Bi2NbxV1−xO5.5 ceramics confirm that the grain size decreases markedly (18 μm to 4 μm) with increasing x. The shift in the Curie temperature (725 K) toward lower temperatures, with increasing x, is established by Differential Scanning Calorimetry (DSC). The dielectric constants as well as the loss tangent (tan δ) decrease with increasing x at room temperature.

Dielectric properties of barium titanium niobates

1997 ◽  
Vol 12 (2) ◽  
pp. 526-530 ◽  
Author(s):  
G. L. Roberts ◽  
R. J. Cava ◽  
W. F. Peck ◽  
J. J. Krajewski
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Low Temperature ◽  
Dielectric Constants ◽  
Partial Substitution ◽  
Dielectric Measurements ◽  
Niobium Oxides ◽  
Polycrystalline Ceramic ◽  
Barium Titanium ◽  
Very Low Temperature

The results of measurements of dielectric constants, in the vicinity of ambient temperature, are presented for eight barium titanium niobium oxides (BaTi1+2nNb4O13+4n for n = 0, 1, 2, 3, 4; Ba3Ti4Nb4O21, Ba3Ti5Nb6O28, and Ba6Ti2Nb8O30) in polycrystalline ceramic form. The dielectric constants are in the range of 30 to 70. The results of dielectric measurements on solid solutions obtained by partial substitution of Ta for Nb are also reported. These substitutions do not dramatically increase the dielectric constants. One material, Ta-substituted Ba3Ti5Nb6O28, has a very low temperature coefficient of dielectric constant at K ≈ 45.

Dielectric Properties of Sol - Gel Silica Glasses

1986 ◽  
Vol 72 ◽  
Author(s):  
G. V. Chandrashekhar ◽  
M. W. Shafer
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Elemental Carbon ◽  
Sol Gel ◽  
Fused Silica ◽  
Dielectric Constants ◽  
Low Dielectric Constant ◽  
Silica Glasses ◽  
Low Dielectric ◽  
Gel Technique

AbstractDielectric properties have been measured for a series of porous and fully densified silica glasses, prepared by the sol-gel technique starting from Si-methoxide or Si-fume. The results for the partially densified glasses do not show any preferred orientation for porosity. When fully densified (˜2.25 gms/cc) without any prior treatment of the gels, they have dielectric constants of ≥ 6.5 and loss factors of 0.002 at 1 MHz, compared to values of 3.8 and <0.001 for commercial fused silica. There is no corresponding anomaly in the d.c. resistivity. Elemental carbon present to the extent of 400–500 ppm is likely to be the main cause for this enhanced dielectric constant. Extensive cleaning of the gels prior to densification to remove this carbon were not completely successful pointing to the difficulty in preparing high purity, low dielectric constant glasses via the organic sol-gel route at least in the bulk form.

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