Electrical Properties Of BaTiO3 Research Articles

Effects of MgO and Rare-Earth Oxides (Y2O3, Yb2O3, Dy2O3) on the Structural Characteristics and Electrical Properties of BaTiO3

This study investigated the impact of MgO and rare-earth oxides (Y2O3, Yb2O3, and Dy2O3) on the structural characteristics and electrical properties of BaTiO3. Specimens sintered at 1350 °C for durations ranging from 1 to 5 h in air exhibited a single phase of BaTiO3 with a tetragonal structure. This was observed for pure BaTiO3 and specimens co-doped with MgO-Y2O3 and/or MgO-Dy2O3. However, a pseudo-cubic structure of BaTiO3 was detected for specimens doped with MgO or co-doped with MgO-Yb2O3. The unit-cell volume of the sintered specimens was found to be dependent on the type of substitution ion for the A/B site of BaTiO3 (ABO3). The dielectric constant (εr) of the sintered specimens decreased with the substitution of MgO and rare-earth oxides due to a decrease in tetragonality (c/a). The electrical resistivities of the sintered specimens were influenced not only by their microstructural characteristics but also by the secondary phases of the sintered specimens. The BaTiO3 specimens co-doped with MgO-Yb2O3 and/or doped with MgO met the EIA X7R and X8R specifications (−55 to 125~150 °C, ΔC/C = ±15% or less), respectively.

High performance flexible piezoelectric nanogenerator based on Bi-doped BaTiO3/polyimide composite films

ABSTRACT Piezoelectric nanogenerators (PENGs) composed of inorganic ceramic nanoparticles and polymer matrix have received extensive attention from scientific researchers. In this article, PENG based on BaTiO3-Bi/Polyimide (BTO-Bi/PI) composite thin films were prepared. The influence of the doping amount of Bi2O3 on the electrical properties of BaTiO3 and the power generation performance of composite thin films were studied in detail. BaTiO3 doped with 0.1 mol% Bi2O3 achieve optimal piezoelectric properties with d33 of 246 pC/N and d33* of 856 pm/V. The flexible BTO-Bi/PI PENG device demonstrates short-circuit current of 365 nA and open-circuit voltage of 17 V, which shows great capability of capturing mechanical energy; it also can be used as sensors under lower mechanical stress and has a wide operating temperature range.

Investigation on structural and electrical properties of Co and W modified BaTiO3

The influence of co-substitution of Co and W on structural and electrical properties of BaTiO3 (i.e., Ba(Co1/3Ti1/3W1/3)O3) was investigated. This perovskite ceramic was synthesized using a conventional ceramic technology (i.e., high-temperature solid state reaction route, calcination temperature = 1100 °C and sintering temperature = 1200 °C). The compound crystallizes in the orthorhombic phase. The Nyquist plots exhibit the activation of grain boundary effect at 300 °C and the Non-Debye behavior in the sample. The relaxation distribution parameter for the sample at different temperatures is calculated from the depression angle of the semicircular arcs in the Nyquist plot. The activation energy of 0.69 eV estimated for the charge carriers in the grain is almost in good agreement with that of 0.66 eV calculated from the relaxation process of grains. The sample possesses a dielectric constant of 1140 and loss tangent of 0.27 at room temperature which can be exploited for some applications including memory devices, etc. The existence of room temperature hysteresis loop confirms the ferroelectric nature of the sample. On the basis of variation of the exponent in the Jonscher's power law with temperature, correlated barrier hopping is favored as the dominant conduction mechanism in the sample.

First Observation of Ferroelectricity in ∼1 nm Ultrathin Semiconducting BaTiO3 Films.

The requirements of multifunctionality in thin-film systems have led to the discovery of unique physical properties and degrees of freedom, which exist only in film forms. With progress in growth techniques, one can decrease the film thickness to the scale of a few nanometers (∼nm), where its unique physical properties are still pronounced. Among advanced ultrathin film systems, ferroelectrics have generated tremendous interest. As a prototype ferroelectric, the electrical properties of BaTiO3 (BTO) films have been extensively studied, and it has been theoretically predicted that ferroelectricity sustains down to ∼nm thick films. However, efforts toward determining the minimum thickness for ferroelectric films have been hindered by practical issues surrounding large leakage currents. In this study, we used ∼nm thick BTO films, exhibiting semiconducting characteristics, grown on a LaAlO3/SrTiO3 (LAO/STO) heterostructure. In particular, we utilized two-dimensional electron gas at the LAO/STO heterointerface as the bottom electrode in these capacitor junctions. We demonstrate that the BTO film exhibits ferroelectricity at room temperature, even when it is only ∼2 unit-cells thick, and the total thickness of the capacitor junction can be reduced to less than ∼4 nm. Observation of ferroelectricity in ultrathin semiconducting films and the resulting shrunken capacitor thickness will expand the applicability of ferroelectrics in the next generation of functional devices.

Multiphase coexistence and enhanced electrical properties in (1-x-y)BaTiO3-xCaTiO3-yBaZrO3 lead-free ceramics

Abstract In this work, the multiphase coexistence of rhombohedral-orthorhombic and orthorhombic-tetragonal (R-O/O-T) was constructed in (1-x-y)BaTiO3-xCaTiO3-yBaZrO3 ceramics with 0.14 ≤ x ≤ 0.16 and 0.10 ≤ y ≤ 0.12, and thus a large piezoelectric constant (d33) of 600 pC/N was attained in the ternary (1-x-y)BaTiO3-xCaTiO3-yBaZrO3 ceramics using the optimization of x and y. The R-O/O-T multiphase coexistence as well as the enhancement of dielectric and ferroelectric properties can be responsible for the high d33 of this work. In addition, a high strain of 0.15% was observed in the multiphase coexistence. As a result, electrical properties of BaTiO3 can be optimized by the construction of multiphase coexistence through the co-doping of CaTiO3 and BaZrO3.

Doping effect of Ta5+ ions on microstructure and electrical properties of BaTiO3–(Bi0.5Na0.5)TiO3 ceramics with positive temperature coefficient of resistivity

Lead-free 0.912Ba0.97TiO3–0.088(Bi0.5Na0.5)TiO3–xTa2O5 (0 ≤ x ≤ 0.005) ceramics with positive temperature coefficient of resistivity (PTCR) were prepared by solid reaction sintering of high-purity metal oxides and carbonates reagents. The doping effect of Ta5+ ions on the microstructure and electrical properties of the samples was investigated. X-ray diffraction analysis indicated that all the samples were of a single tetragonal perovskite structure with the calculated c/a value first increased and then decreased with increasing x. The Raman shift at 305 cm−1 became strong firstly and then declined, and the broad band at 722 cm−1 narrowed initially and then broadened with the increase in Ta5+ content. The Curie temperature raised first and then decreased, presenting the highest value up to 170 °C for the samples with x = 0.001. Moreover, after the incorporation of Ta5+ ions, the PTCR (defined by the resistivity jump with the ratio of maximum to minimum ones) decreased first and then increased, presenting the best PTCR performance for the samples with x = 0.005. And with increasing x, the room temperature resistivity decreased first and then increased, displaying the lowest room temperature resistivity for the samples with x = 0.003.

Investigation on the Correlation between Structural and Electrical Properties of Lanthanum Doped Barium Titanate Ceramics

The structure-property relationship of 0.3, 0.5 and 0.7mole% lanthanum (La2O3) doped Barium titanate (BaTiO3) ceramics prepared by solid state sintering under different sintering conditions were investigated in this research. The raw materials were La2O3 (grain size=~80nm) and BaTiO3 (grain size=100nm) powders. Field Emission Scanning Electron Microscope (FE-SEM) was used to examine grain size and surface morphology of sintered pellets & X-Ray Diffraction analysis was conducted to identify crystal structure. The results showed significantly improved grain size and electrical properties of BaTiO3 for 0.5 mole% La2O3 with desired grain size (0.8-1.3μm), high densification (>90% theoretical density) and stable dielectric constant (12700) at room temperature (f=100Hz) by lowering curie temperature around 30oC by sintering at 1300oC for 8 hrs. A gradual deterioration follows with increased doping concentration. So the research revealed that proper La3+ concentration can inhibit grain size and lower Curie temperature hence significantly improving the electrical properties of BaTiO3 ceramics.

Microstructure and electrical properties of BaTiO3-(Bi0.5M0.5)TiO3 (M=Li, Na, K, Rb) ceramics with positive temperature coefficient of resistivity

Lead-free 0.912Ba0.97TiO3-0.088(Bi0.5M0.5)TiO3 (M=Li, Na, K, Rb) ceramics with positive temperature coefficient of resistivity (PTCR) were prepared by conventional solid sintering reaction using high-purity reagents of metal oxides and carbonates. The effect of (Bi0.5M0.5)TiO3 (M=Li, Na, K, Rb) doping on the microstructure and electrical properties of the samples were investigated. X-ray diffraction analysis indicated that all the samples were of a single perovskite structure with tetragonal phase, and the calculated c/a value increased first and then decreased. The Raman shift at 305cm−1 became strong first and then declined when M in the dopant (Bi0.5M0.5)TiO3 was changed from Li to Rb. The Curie temperature of the samples displayed a tendency to increase first and then decrease, in which BaTiO3-(Bi0.5K0.5)TiO3 ceramics presented the highest value. Moreover, after the incorporation of alkali ions, the PTCR value (defined by the resistivity jump with the ratio of the maximum to minimum) and room temperature resistivity of the samples decreased first and then increased, in which BaTiO3-(Bi0.5Na0.5)TiO3 ceramics possessed the lowest room temperature resistivity.

Thermal stability and local atomic structure of (Na0.5K0.5)NbO3 doped BaTiO3 ceramics

Dielectric properties of x(Na0.5K0.5)NbO3–(1−x)BaTiO3 (x=0.00 and 0.06) specimens were investigated in terms of changes in local atomic structure, according to the phase transition by elevating the overall temperature. A 0.06(Na0.5K0.5)NbO3–0.94BaTiO3 (NKN–BT) specimen exhibited enhanced temperature stability along with an increased dielectric constant. The degree of reduction in tetragonality (c/a) at the Curie temperature was smaller in NKN–BT compared to that in pure BaTiO3, as calculated by Rietveld refinement. From a comparison of the pre-edge region in the Ti K-edge, it was determined that the off-center displacement of the Ti atom was also raised to 13.4% through NKN substitution, with a change in local orientation from the [001] to the [111] directions. The substitution by NKN, which has a different ionic radius and electrical charge compared with BaTiO3, causes structural distortion of the TiO6 octahedra in the NKN–BT lattice, resulting in local polarization. These structural changes lead to the temperature stability of the dielectric constant and an overall improvement in the electrical properties of BaTiO3.

Phase boundary design and high piezoelectric activity in (1−x)(Ba0.93Ca0.07)TiO3-xBa(Sn1−yHfy)O3 lead-free ceramics

The (1−x)(Ba0.93Ca0.07)TiO3-xBa(Sn1−yHfy)O3 (BCTSH-x-y) lead-free ceramics were synthesised by the conventional solid-state reaction method, and the influences of doping elements (Ca, Sn, Hf) content on their phase structure, microstructure, and electrical properties were systematically investigated. The phase boundaries concerning the orthorhombic and tetragonal (O-T) phases were found in the 0.925(Ba0.93Ca0.07)TiO3-0.075Ba(Sn1-yHfy)O3 ceramics with 0 ≤ y ≤ 0.25, and then the enhanced piezoelectric properties with d33 ∼ 550 pC N−1 were obtained. In addition, the addition of Hf can also improve the Curie temperature (TC) and ferroelectric properties of the ceramics. As a result, the electrical properties of BaTiO3 can be optimized by the construction of phase boundaries through Ca, Sn, and Hf co-doping.

Powder characterization and electrical properties of BaTiO3 produced by several powder synthesis methods

Powder characterization and electrical properties of BaTiO3 produced by several powder synthesis methods

Effect of Li3PO4 addition on the sintering temperature, phase, microstructure, and electrical properties of BaTiO3

Decreasing the sintering temperature of BaTiO3 without deteriorating the dielectric properties is technologically important in the fabrication of multi-layer ceramic capacitors (MLCCs). Consequently, ceramic formulations based on the (1 − x)BaTiO3–xLi3PO4 (x = 0, 0.01, 0.03, 0.05, and 0.1) were prepared. The use of Li3PO4 as a sintering aid lowered the optimum sintering temperature from 1350 to 1150 °C but X-ray diffraction revealed the formation of BaLiPO4 for x = 0.01–0.05 and an additional secondary LiPO3 phase at x = 0.1. The room temperature dielectric constant decreased from ~4288 to ~3600 and the remnant polarization and coercive field also decreased from 6.70 to 3 µC/cm2 and 3.32 to 2.5 kV/cm, respectively, as x increased from 0 to 0.05 but more importantly the phase transition temperature remained essentially constant, an important factor in the fabrication of temperature stable devices. Moreover, the bulk and grain boundary conductivity decreased as x increased to 0.05, possibly related to a decrease in the grain size from 50 to 1 μm. These results suggest that Li3PO4 may have technological benefits in the fabrication of MLCCs.

Substitution behavior of x(Na0.5K0.5)NbO3-(1 − x)BaTiO3 ceramics for multilayer ceramic capacitors by a near edge x-ray absorption fine structure analysis

The doping effect of (Na0.5K0.5)NbO3 (NKN) as alternatives for rare-earth elements on the electrical properties of BaTiO3 has been investigated, in terms of their substitution behavior. The dielectric constant of a specimen with x = 0.05 was about 79% higher than that of pure BaTiO3, and the temperature coefficient of capacitance was satisfied by the X7R specification. The specimen with x = 0.05 showed the lowest tetragonality among the four compositions and had a fine grain size of <2 μm. Although the addition of NKN decreased the specimen's tetragonality, the electrical properties were enhanced by the formation of defect dipoles and conduction electrons, which resulted from an acceptor and donor substitution behavior. Through O K-edge near edge x-ray absorption fine structure spectroscopy, the practical substitution behavior was defined by the change in Ti 3d orbital states. The energy separation of the Ti 3d orbitals was more apparent with the specimen of x = 0.05, which is related to the donor level from the donor substitution of Nb5+ ion for Ti-sites. Therefore, the simultaneous substitution of Na+/K+ and Nb5+ ions into BaTiO3 can improve dielectric properties, based on the charge-transfer process.

Densification, Microstructure, and Electrical Properties of BaTiO3 (BT) Ceramics Prepared from Ultrasonically De-Agglomerated BT Powders

In this study, a correlation between densification, microstructure, and electrical properties of BaTiO3 (BT) ceramics prepared from ultrasonically de-agglomerated BT powders has been analyzed. BT powders with the same crystal structure (tetragonal) and stoichiometry, but with different average particle size, were used to prepare sintered ceramics. Densification and electrical properties of the sintered BT ceramics were correlated to the average particle size of the powders. It was found that a decrease in average particle size improved the densification process as well as the ceramics' microstructure. The impedance measurements were done up to 320°C in order to separate grain (bulk) and grain boundary contributions. Bulk resistance was more or less the same, independent on the average particle size of the powder. On the contrary, grain boundary resistance increased with decreasing average particle size of the powder.

Microstructure and electrical properties of BaTiO3 and (Ba,Sr)TiO3 ferroelectric thin films on nickel electrodes

Nickel thin films have been sputtered on standard Si/SiO2 substrates with TiO2 as an adhesive layer. The thermal stability of these substrates was analyzed. SEM images show an increase in grain size with annealing temperature. They were found to be stable till 800°C, beyond which the nickel layer disintegrated. These substrates were used for deposition of BaTiO3 and (Ba,Sr)TiO3 dielectric thin films under a reducing atmosphere. The dielectric thin films were processed with various pyrolysis and annealing temperatures in order to optimize the dielectric properties. Increased pyrolysis temperatures showed an increase in the grain size. Results on these nickelised substrates were finally compared with dielectric films deposited on platinized silicon substrates under identical conditions but crystallized in an oxygen atmosphere.

Electrical Properties of Dy2O3-Doped BaTiO3

The effects of Dy addition on the electrical properties of BaTiO3 have been studied by analyzing equilibrium electrical conductivity as a function of temperature, oxygen partial pressure (Po2) and composition. In(Ba1-xDyx)TiO3+0.5x, the conductivity follows the -1/4th power dependence of Po2 at high oxygen activities, which supports the notion that cation vacancies are generated to compensate for Dy donors, and is nearly independent of Po2 where electron compensation prevails at a low Po2. The incorporation of “Dy3+” ion into Ti sites up to 2.0 mol% showed the typical acceptor-doped behavior of the Dy3+ ion. Curie temperature (Tc) was systematically decreased when the Dy3+ ion was incorporated into Ti sites.

Effect of poly(acrylic acid) and poly(vinyl alcohol) on the solubility of colloidal BaTiO3 in an aqueous medium

The influence of poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) on Ba dissolution from the BaTiO3-aqueous solution interface was investigated. Incongruent dissolution of Ba impacts the colloidal stability, microstructure, and electrical properties of BaTiO3 and related perovskite dielectric materials used in the manufacture of ceramic capacitors. The solubility characteristics of BaTiO3 were influenced significantly by the presence of PAA and PVA. PAA, which forms weak monodentate complexes with Ba2+, acted as both a passivating and a sequestering agent, depending on pH. Both PAA and PVA provided some degree of passivation in the acidic pH region. Above pH 8, where BaTiO3 solubility decreases sharply, PVA had a moderate passivating effect, whereas solubility was enhanced by PAA with a positive linear dependence on concentration. The adsorptive and electrokinetic behavior of colloidal BaTiO3 with respect to PAA and PVA are correlated with the observed passivating and sequestering properties of these polymers.

Study of the defect chemistry of Ca-doped BaTiO3ceramics

Abstract The characteristics of Ca2+ in BaTiO3 are of considerable interest. In this paper, measurements of high temperature equilibrium conductivity and positron annihilation have been used to analyze the effects of two kinds of substitution (equivalent and nonequivalent) of Ca2+ on the defect structure and electrical properties of BaTiO3. The results show that the equivalent substitution of Ca2+ can change the enthalpy of oxidation and reduction reactions in different directions. The partial occupation of the Ti-site by Ca2+ causes a marked influence on the electrical conductivity and positron lifetime of BaTiO3. The solid solubility of Ca2+ at the Ti-site of BaTiO3 is confirmed by the analysis of defect chemistry and the positron annihilation technique. Equivalent substitution of Ca2+ has no substantial effect on the resistivity of BaTiO3 sintered in a reducing atmosphere. A small amount of Ca2+ ions incorporated into the Ti-site may increase the resistivity of BaTiO3 by more than ten orders of magnitu...

Behaviour of acceptor states in semiconducting BaTiO3 and SrTiO3

The semiconductivity inMTiO3 (M=Ba, Sr) in the temperature range of practical applications is greatly influenced by the electronic charge redistribution among the acceptor states, arising from the frozen cation vacancies as well as the transition metal ion impurities. The conductivity measurements and defect chemistry investigations above 800 K indicate that the predominant lattice defects areM− and oxygen vacancies. There is dominantp-type conduction at higherP O 2 values in acceptor doped materials at high temperatures. However, they are insulating solids around room temperature due to the redistribution of electrons between the neutral, singly-or doubly-ionised acceptor states. Results fromepr and resistivity measurements show that the above charge redistribution is dependent on crystal structure changes. Hence the electron or hole loss by the acceptor states is influenced by the soft modes which also accounts for the differences in electrical properties of BaTiO3 and SrTiO3. The results are also useful in explaining the positive temperature coefficient in resistance and some photo-electrochemcial properties of these solids.

Study of the Electrical Properties of BaTiO3Doped with Antimony

ABSTRACTThe electrical properties of BaTiO3 doped with Sb have been studied. The nature of variation of ∈ and tan δ with temperature in this material shows that, under the doped conditions, the mechanism of polarization changes from spontaneous to that of relaxation after curie temperature. This supposition is also verified from the study of variation of permittivity with different levels of applied r.f. power at temperatures higher than that of curie. Further, the dielectric hysteresis loops of this material corresponding to various applied voltages were also studied both at a temperature below curie and a temperature above curie. The loops corresponding to the temperature below that of curie showed saturation while those corresponding to the temperature above curie did not show saturation, thus giving another proof of this supposed existence of relaxation polarization in this doped material at that temperature.