Dielectric Properties Of BaTiO3 Research Articles

Effect of Lithium Fluoride on the Dielectric Properties of Barium Titanate

The purpose of this study was to investigate the dielectric properties of BaTiO3 (BTO) ceramics sintered with the aid of lithium fluoride. BTO with various ratios BaO/TiO2 (0.97, 1.00, 1.03) was synthesized by calcination of BaCO3 and TiO2 at 1100 °C. The different BTO powders were mixed with 1, 2 or 3 wt.% of LiF and then wet-ground in ethanol. The mixtures were cold-pressed to pellets with “latex” as a binder. The disks were sintered in free-air or sealed tube at 750, 850, 950 or 1100 °C, respectively, for 2 or 8 h. The obtained ceramics were checked by X-ray diffraction, scanning electron microscopy, differential thermal analyses and Auger microprobe. Dielectric measurements were carried out under vacuum at 1 kHz in the temperature range 180–500 K. Chemical analyses were performed and lithium and fluorine losses were calculated. Results show that the addition of LiF to BTO lowered both the sintering temperature and the ferroelectric Curie temperature T C. Most ceramics exhibited a broad maximum of the permittivity $${\varepsilon_{\rm r}^{\prime}}$$ and small dielectric losses tan $${\delta}$$ at T C. The best dielectric characteristics were observed from BTO (1.03) ceramic sintered with 2 wt.% of LiF at 950 °C for 2 h and then reheated at 1200 °C for 2 h in sealed tube: T C = 248 K, $${\varepsilon_{\rm r}^{\prime}}$$ at T C = 8650, tan $${\delta}$$ at T C = 6 × 10−3. The majority of prepared ceramics could be of interest in the manufacture of Z5U multilayer capacitors at low factory cost.

Effects of Ca Addition on Chemical Composition, Microstructure and Dielectric Properties of BaTiO<sub>3</sub>

Owing to its high dielectric constant, barium titanate is a material commonly employed in fabrication of high energy density capacitors. Dielectric properties required for practical applications can be attained in barium titanate with desired chemical composition and microstructure. This study, therefore, aims at examining effects of additive contents on formation of secondary phases, microstructure and dielectric properties of BaTiO3 and BaTiO3 with 20-40 at% Ca. Chemical composition analysis revealed that single-phase BaTiO3 powder could be attained by the solution combustion technique. However, the powder with high Ca content exhibited large quantities of secondary phases. Dielectric property measurements of the uniaxially pressed powders indicated that dielectric constants could be enhanced with low Ca content. On the contrary, dielectric constant significantly degraded with high Ca content. This was attributed to formation of large quantities of secondary phases, coarse grain size and low density. Values of dielectric loss of all materials were lower than 1%.

Effect of Variable Valence Ion Doping on the Dielectric Properties of BaTiO3–Based Materials

Dielectric properties of BaTiO3, BaTiO3 + 0.1 wt.% Fe2O3 and BaTiO3 + 1 wt.% Fe2O3 ceramics were studied. The dielectric measurements were performed at the temperature ranging from 130 K to 500 K and at the frequency ranging from 0.1 Hz to 10 MHz. Phase transitions were also determined by a thermal analysis in a wide temperature range. Both thermal analysis and electrical characterization techniques show that the temperature of phase transition is shifted towards lower temperatures with increasing Fe2O3 content. The changes and diversity of the observed phase transition temperatures occurred as a consequence of the ion substitution. Such behaviour of the investigated polycrystalline materials may be due to the multivalence nature of the incorporated ions.

3D dependence of the dielectric dispersion in a BaTiO3 single crystal

The 3D dependences ɛ′(log f, T) and tanδ(logf, T) of a perfect BaTiO3 single crystal grown by the Remeika method have been studied in the ranges f = 1–2 × 107 Hz and T = −80–130°C. These dependences characterize a transition from the paraelectric phase (121.5°C) as a near-antiferroelectric transition followed by the transition to the tetragonal phase at ∼79.5°C. According to a number of signs, the range 121.5–79.5°C corresponds to a metastable phase typical of first-order phase transitions. The unexpected result of this work has been discussed with invoking the hypothesis on the BaTiO3 structure in the paraelectric phase, according to which it consists of three antiferroelectric states oriented along the crystallographic axes. Using the dielectric properties of BaTiO3 as an example, the method of direct correct determination of the temperatures of the structural transformations from the anomaly of tanδ(logf, T) has also been demonstrated.

Synthesis and Characterization of Strontium Doped Barium Titanate Ceramics

In order to investigate effect doping with strontium on structural and dielectric properties of BaTiO3, a series of B1-xSrxTiO3 (BSxT) ceramic powders (0, 0.05, 0.1, 0.15, 0.2, 0.3, 0.4 and 0.5) were prepared by the sol gel method. The phase formation and crystal structure of BaTiO3 were checked by X-ray diffraction analysis and Raman spectroscopy. It was observed that the quadratic structure of the pure sample transforms to pseudo cubic under Sr substitution. The morphology and microstructure of the samples were examined by scanning electron microscopy (SEM); a quiet regular morphology in shape was observed with an average grain size of 2 m in accordance with that reported in the literature. The dielectric investigations show that BST is a classical ferroelectric material and that the temperature of the maximum of the permittivity, Tm, decreases with Sr content.

Effect of SnO2 concentration on the dielectric properties of BaTiO3–(Sr1−1.5xBix)TiO3 ceramics

SnO2-doped 0.45BaTiO3–0.55(Sr1−1.5xBix)TiO3 (BT–SBT) ceramics were prepared by the conventional solid state reaction method. The effect of SnO2 concentration on the microstructures and dielectric properties has been investigated. XRD results indicate all the specimens have a perovskite structure without any secondary phases. With increasing SnO2 concentration, the maximum dielectric constant decreases with slight shift in Curie temperature and the peak in temperature spectra becomes much broader. When the SnO2 concentration is 1 mol%, the specimen exhibits a more homogeneous microstructure and an improvement of the dielectric breakdown strength compared with the undoped one. Impedance analysis was carried out to investigate the trend in activation energy with the increase of SnO2 concentration. The correlation between the dielectric breakdown strength and the difference of the activation energies of grain and grain boundary was qualitatively discussed. The accumulation of space charge was found to enhance the dielectric breakdown strength.

Effect of Al and Mg Doping on Dielectric Properties of BaTiO3 Synthesized by Solution Combustion Technique

It has been accepted that doping and parameters related to synthesis and processing of ceramic samples could affect dielectric properties. This study aimed at synthesizing BaTiO3 BaAl0.1Ti0.9O3 and BaMg0.1Ti0.9O3 powders by the solution combustion technique and examining their dielectric constants and dielectric losses. Initial powder exhibited average particle size in sub-micrometer range. Grain sizes in micrometer range were observed in the pressed and sintered samples. Dielectric constants and dielectric losses of the samples ranged from 52.2 to 91.4 and 3.3 × 10−3 to 4.7 × 10−3 at 1 MHz, respectively. BaMg0.1Ti0.9O3 samples achieved the highest dielectric constant, while BaAl0.1Ti0.9O3 samples exhibited the lowest dielectric constant. Enhancement of the dielectric properties was attributed to smaller grain sizes, while lower density in the samples resulted in reduced dielectric constants.

Effect of fluxing additive on sintering temperature, microstructure and properties of BaTiO3

Various fluxing materials are added to technical ceramics in an attempt to lower their sintering temperatures and make their processing economical. The effect of 0·3 wt% Li2CO3 addition on the phase, microstructure, phase transition temperatures and dielectric properties of BaTiO3 was investigated in the present study. The addition of 0·3 wt% Li2CO3 was observed to lower the optimum sintering temperature by ∼200°C with no second phase formation and cause a five-fold reduction in grain size. Rhombohedral-to-orthorhombic and tetragonal-to-cubic phase transitions at the expected temperatures were evident from the Raman spectra, but the orthorhombic-to-tetragonal phase transition was not clearly discernible. The persistence of various phase(s) at higher temperatures in the flux-added materials indicated that the phase transitions occurred relatively slowly. A decrease in dielectric constant of Li2O-added BaTiO3 in comparison to pure BaTiO3 may be due to the diminished dielectric polarizability of Li + in comparison to Ba2 + .

Preparation and dielectric properties of BaTiO3-based X8R ceramics co-doped with BIT and CBS glass

The effects of Bi4Ti3O12 (BIT) on phase purity and dielectric properties of BaTiO3 (BT) ceramics have been investigated. Results show that BT samples doped with 1–3 mol% BIT adopt a single phase. However, secondary phase Bi2Ti2O7 is observed when BIT content exceeds 3 mol%. Tetragonality and the Curie temperature (TC) firstly increase and then decreases with an increase in BIT content. The 3 mol% BIT-doped BT ceramic sintered at 1,250 °C exhibits good dielectric properties of er = 2,692, tan δ = 0.0152, ρv = 5.8 × 1012 Ω cm, and the variation of dielectric constant as compared with that at room temperature is about −20 % at −55 °C and less than 11 % at 150 °C. It is found that the addition of calcium borosilicate glass (CBS) in BT-BIT ceramics can effectively lower the sintering temperature from 1,250 to 1,050 °C and further enhance the capacitance temperature stability. The permittivity decreases with an increase in CBS content from 1 to 10 wt%. Secondary phase BaBi4Ti4O15 exists in the CBS doped BT-3BIT systems. All of CBS doped samples satisfy the X8R specification. Typically, the sample with 3 wt% CBS has er = 1,789, tan δ = 0.0115, ρv = 9.67 × 1012 Ω cm. The variation of permittivity as compared with that at room temperature is about −12 % at −55 °C and less than ± 11 % at 150 °C. The as-prepared materials have great potential as EIA X8R-type multilayer ceramic capacitors.

Structure and dielectric properties of BaTiO3–BiScO3 ceramics sintered by CaF2–4LiF aids

The effect of CaF2–4LiF (1–5 mol.-%) on the phase structure, microstructure and dielectric properties of 0·9BaTiO3–0·1BiScO3 (0·9BT–0·1BS) ceramics has been investigated. The 0·9BT– 0·1BS with CaF2–4LiF dopant ceramics sintered at 1100°C show a pure perovskite structure. Results show that CaF2–4LiF dopant can improve the sintering ability of 0·9BT–0·1BS ceramics when CaF2–4LiF content is below 3 mol.-%. The ceramics with 3 mol.-%(CaF2–4LiF) sintered at 1100°C exhibit a high permittivity, low dielectric loss as well as flat ϵ′ v. temperature curve indicating a favourable temperature stability, which are listed as follows: ϵ′25°C=1483, tan δ25°C=0·00309, Δϵ′/ϵ′25°C ≤ ± 13% at 100 kHz, in the temperature range from –55 to 150°C. This low sintering temperature allows using relatively inexpensive internal electrodes in the production of future capacitors.

Microstructure and dielectric properties of BaTiO3-CeO2-SnO2 ceramics

We have studied the effect of codoping with CeO2 and SnO2 (2 to 3.5 wt %) on the microstructure and dielectric properties of BaTiO3. Doping with CeO2 and SnO2 inhibits grain growth in BaTiO3 and enables the fabrication of ceramic materials with a grain size below 1 μm. The temperature coefficient of permittivity of the ceramics increases with CeO2 + SnO2 content, firing temperature, and firing time.

Effects of Rare-Earth Oxides on Time-Dependent Dielectric Properties of Mn-Doped BaTiO3

The effects of rare earth oxides on dielectric properties of BaTiO3 have been investigated. The addition of R2O3 (R: Dy, Ho, Yb) significantly decreased the capacitance change with time under a DC electric field. Yb-doped specimens exhibited the lowest aging rate in the second stage, which is due to the larger population of defect dipoles associated with oxygen vacancies. The DC bias aging behavior of Mn-doped BaTiO3 was also suppressed by rare-earth oxides. The addition of rare-earth oxides led to an increase in the leakage current of BaTiO3. Specimens codoped with rare-earth and manganese oxides showed lower leakage currents with moderate DC bias aging rates.

Physical and dielectric properties of BaTiO3–fluoride–glass systems for nitrogen-fireable embedded capacitors

BaTiO3-based dielectrics containing the selective additive combinations from Pb-free glasses and fluoride compounds such as AlF3, BaF2, CaF2, LiF and ZnF2 were studied mainly for a potential N2-fireable embedded capacitor in printed circuit board with Cu metallization. The physical and dielectric properties, such as dielectric constant (k), loss tangent (tanδ) and Tc, strongly depended on the choice of additive combination. A bismuth borosilicate glass was most promising in terms of the degree of densification and dielectric constant. The samples containing LiF and ZnF2 and sintered at 950 °C looked most beneficial in that these additives produced high k of >1,200 and low tanδ of < 0.022 at room temperature regardless of sintering atmosphere. As an example, the 95BaTiO3–2LiF–3(Bi borosilicate) sample exhibited k ~ 1,340 and tanδ ~ 0.022 at room temperature when fired at 950 °C in N2.

Phase structure and dielectric properties of doped BaTiO3 ceramics

The effects of two rare earth oxides such as CeO2 and Sm2O3 on the phase structure and dielectric properties of BaTiO3 ceramic were investigated. Results indicate that the dielectric constant of this system will increase greatly with the increasing content of these two oxides, and Ce(superscript 4+) substitutes for Ba(superscript 2+) located at A-site in ABO3 structure Quantitative XRD analysis shows that c/a ratio in the sample with addition of CeO2 will increase, which implies the increase of tetragonality in system, causing the augment of dielectric constant, and the decrease of the crystal’s geometrical symmetry results in curie-temperature moving towards low temperature; Sm(superscript 3+) (0.096 nm) substitutes for Ba(superscript 2+) (0.135 nm) possessing larger radius in A-site and the electrovalency in A-site increases, the mutual effect is strengthened, so the polarization is enhanced, and the dielectric constant increases notablely.

Significantly enhanced low-frequency dielectric permittivity in the BaTiO3/poly(vinylidene fluoride) nanocomposite

To disclose an effect of ceramic particle size on dielectric properties of BaTiO3/ poly(vinylidene fluoride) (BT/PVDF) composites at low frequency, the dielectric properties of the BT/PVDF composites loaded with different diameter BT particles at the same volume concentration were studied at wide frequency ranges from 10−1to107Hz. A significant low-frequency dielectric permittivity increase in the BT/PVDF nanocomposite was noticed, which was not reported previously. The authors considered that the marked aggrandizement of interface and dipole polarization at low frequency is charged with the significant increase in dielectric permittivity.

Doping effects of Mn2+ on the dielectric properties of glass-doped BaTiO3-based X8R materials

In this paper, Mn2+ and calcium borosilicate glass (CBS) were used as effective dopants to prepare environmentally friendly dielectric materials satisfying EIA X8R specification. The effects of various Mn2+ concentrations on the dielectric properties of BaTiO3 (BT) ceramics were investigated when CBS amount was fixed. The dielectric measurements showed that the permittivity was decreased continuously with increasing Mn2+ concentrations, resulted from the existence of paraelectric regions caused by Mn2+ doping. The dielectric loss was decreased at the beginning and then increased with increasing Mn2+ concentrations, whereas the resistivity showed an opposite movement. The SEM images and X-ray diffraction curves corresponding to BT ceramics doped with different Mn2+ amounts proved that Mn2+ can promote the crystallization of CBS glass to form the secondary phase Ca4Mn4Si8O24, which determines the intensity of the high temperature peak (at about 125 °C) of the variation rate curve of capacitance. Moreover, the modification effects of Mn2+ on the dielectric properties of BT have been investigated. It is revealed that a proper usage of Mn2+ can improve the dielectric properties significantly, and Mn2+ and CBS co-doped BT ceramics are promising to develop X8R MLCs.

Effect of Oxygen Cooling Environment on the Structural Characteristics and Dielectric Properties of BaTiO3 and SrTiO3 Thin Films

The BaTiO3 (BTO) and SrTiO3 (STO) thin films have been fabricated on (La,Sr)CoO3/MgO (100) single crystal substrate by pulsed laser deposition (PLD). The effect of oxygen content in the BTO and STO lattices on their structural characteristics and dielectric properties has been investigated. The variation of the oxygen content was made in BTO and STO thin (10 nm) films by changing oxygen cooling pressure from 10−3 Torr to 400 Torr. The lattice parameter of STO thin film was sensitive to the variation of the oxygen pressure while that of BTO thin film was not sensitive to the oxygen pressure. The volume of the STO thin film increased with decreasing the oxygen cooling pressure, which is attributed to the volume change caused by oxygen nonstoichiometry (deficiency). The dielectric constant of the STO thin film was insensitive to the oxygen cooling pressure. This result indicates that the dielectric constant of the STO thin film was not influenced by the oxygen deficiency, although the STO thin film was influenced by the oxygen environment and had oxygen deficient nonstoichiometry. Those results suggest that the lattice distortion is the most important factor to influence the dielectric property of specifically STO thin films. On the other hand, the BTO thin film was not susceptible to the change in the oxygen environment, resulting in insensitive lattice parameter and volume as well as the dielectric constant to the oxygen environment.

Dielectric Properties of BaTiO3 Based Lead Free Relaxor Prepared Through Conventional and Microwave Sintering

Dielectric ceramics with compositions belonging to the Ba(Nd x Ti1−2x Nb x )O 3 with varying concentration of x were prepared through Solid State Sintering route using both conventional and microwave sintering. The phase transformations were studied by dielectric measurements in a wide range of temperature and frequency. The relaxor behaviour is almost favoured as the composition deviates more from BaTiO 3 and as the substitution is heterovalent in the 6-coordination number crystallographic site.

Effect of doping Ca ions on structural and electrical properties of Ba(Zr0.05Ti0.95)O3electroceramics

Polycrystalline samples of (Ba1−zCaz)(Zr0.05Ti0.95)O3 (z=0, 0.03, 0.06 and 0.09) (BCZT) belonging to perovskite ferroelectric were prepared by a high-temperature solid-state reaction technique. Preliminary room temperature X-ray study confirmed the formation of a single phase compound in orthorhombic crystal structure. Detailed studies of dielectric parameters as a function of temperature at 10 kHz suggests that the substitution of Ca2+ ion at the Ba-site and Zr4+ at Ti-site has a strong effect on the dielectric properties of BaTiO3.

Preparation and dielectric properties of BaTiO3⁄SrTiO3 artificial superlatices

Preparation and dielectric properties of BaTiO3⁄SrTiO3 artificial superlatices