Bismuth Titanate Research Articles

Quantitatively Analyzing Pressure Induced Phase Transformation by Photoluminescence Spectra in Eu3+-doped Sodium Potassium Bismuth Titanate.

(Na0.8,K0.2)0.5Bi0.497Eu0.003TiO3 (NKBET20) piezoelectric ceramic powders were prepared by the solid-reaction method. The phase structures of the NKBET20 powders under various pressures were investigated by photoluminescence (PL) spectra and X-ray diffraction (XRD). The PL spectra of the doped Eu3+ ions suggest a pressure induced transformation from the tetragonal to rhombohedral phase (R phase), and the phase transformations were confirmed by XRD analyses. Furthermore, the fluorescence intensity ratio of the transition to the transition (FIR21) could be utilized for the quantitative analyses of the phase transformation. The results from the PL method show that as the pressure increases from 0 to 500 MPa, the fractions of the R phase of the NKBET20 powders increase from about 11% to 58%, while the fractions of the tetragonal phase (T phase) decrease from about 89% to 42%, which are consistent with the XRD Rietveld refinement. Unlike the ceramic bulks, the pressure induced phase transformation in the ceramic powders shows no obvious trigger point and is much gentler. This work suggests a different viewpoint to study the pressure induced phase transformation qualitatively and quantitatively, which can be used for more phase analyses.

Significant ion conduction in Cu acceptor-substituted bismuth titanate polycrystalline ceramics

This paper reports that Cu acceptor substitution at the Ti site has significant effects on structure and electrical properties of Aurivillius-phase Bi4Ti3O12 polycrystalline ceramics. Phase purity, microstructure and defect chemistry of Bi4Ti3−xCuxO12−x (BiT–100xCu, x = 0–0.12) are characterized by XRD, SEM, EDS and EPR measurements. Neutron diffraction refinement indicates that BiT–8Cu has an orthorhombic symmetry [space group: B2cb; lattice parameters: a = 5.4116(1) A, b = 32.833(1) A, c = 5.4479(1) A and V = 967.98(5) A3]. Impedance spectra of BiT–100xCu were measured under variable oxygen partial pressure (pO2). Bi4Ti3O12 shows mixed electronic (hole) and ionic conduction owing to the existence of oxygen vacancies ($$ {\text{V}}_{\text{O}}^{ \cdot \cdot } $$) arising from the loss of Bi2O3 during sintering. Interestingly, bulk conductivity in Cu-substituted Bi4Ti3O12 ceramics is predominately ionic due to the fact that there are considerably additional oxygen vacancies introduced into the perovskite lattices. The optimum composition of BiT–8Cu shows high ionic conductivity in the bulk with a value of ~ 0.007 S/cm at 650 °C.

Enhanced mechanical energy harvesting capability in sodium bismuth titanate based lead-free piezoelectric

The demand for high-performance lead-free piezoelectric materials towards mechanical energy harvesting has been driven by the continuous requirements of self-powered applications such as wireless sensor network systems and biomedical devices, etc. Herein, manganese-doped sodium bismuth titanate based lead-free ternary piezoelectric system 0.92(Na0.5Bi0.5)TiO3-0.04(K0.5Bi0.5)TiO3-0.04BaTiO3 (NBT-KBT-BT) was developed and the critical role of manganese on tailoring the microstructure and electrical properties was investigated. The highest piezoelectric coefficient (d33) of 140 pC/N with figure of merit (d33 × g33) of 1790 × 10−15 m2/N has been achieved. Both high open-circuit voltage of ∼12.2 V and power density of ∼0.37 μW/mm3 were obtained based on cantilever-type energy harvester. This work provides a promising paradigm for the development of high-performance mechanical energy harvesting devices by tailoring the composition of lead-free piezoelectric ceramics.

Enhanced physical properties of Bi4Ti3O12 modified Bi0.5(Na0.4K0.1)TiO3 lead-free piezoelectric ceramics using crystallographic orientation techniques

In this study, bismuth titanate (Bi4Ti3O12) templates were synthesized through the molten salt method in Na2CO3 and K2CO3 fluxes. The prepared Bi4Ti3O12 templates possessed plate-like morphologies with lengths of 5–20 μm and widths of 0.5–1 μm. They can be used to improve the electrical properties of Bi0.5 (Na0.4K0.1)TiO3 lead-free ceramics by employing template grain growth method at different sintering temperatures (950–1150 °C). The effect of sintering temperature on the physical properties of the 0.9[Bi0.5(Na0.4K0.1)TiO3]-0.1[Bi4Ti3O12] (BNKT-BT) ceramics was investigated and it was found that the degree of orientation of the synthesized ceramics increased along with the sintering temperature, and the highest values were achieved at 1050 οC. However, at 1150 οC, the values for both ceramics started to decrease due to the formation of the Bi2Ti2O7 pyrochlore phase. The ceramics sintered at an optimum temperature of 1050 οC exhibited the best physical properties such as density (ρ), 6.0 g cm−3 (relative density 99.8% of the theoretical value); remanent polarization (Pr), 15.5 μC cm−2; coercive field (Ec), 24.5 Kv/cm; and highest dielectric constant (emax), 6080.

Optical thermometry based on upconversion emission of Yb3+/Er3+ codoped bismuth titanate microcrystals

Optical thermometry has drawn great attention due to its sensitive and noncontact properties. Herein, Yb3+/Er3+ codoped Bi4Ti3O12 phosphor microcrystals have been synthesized by solid phase reaction for optical temperature sensing. The phase, microscopic structure and morphology of the prepared sample have been studied by the X-ray diffraction, transmission electron microscopy, etc. The process of upconversion emission has been researched with different environmental temperature and excitation power under 980 nm laser excitation. Meanwhile, the temperature sensing nature of the as-prepared microcrystals has been investigated based on the luminescence intensity ratio of two thermally coupled energy levels (Er3+:2H11/2, 4S3/2). The excitation laser power density is 3.95 mW/mm2, and the absolute sensitivity reaches 0.0046 K-1. The result demonstrates potential of the Bi4Ti3O12:Yb3+/Er3+ microcrystals in making optical sensing device under low excitation power density.

New higher temperature and high performance barium titanate and sodium bismuth titanate based piezoelectric ceramics

Ba(NdxTi1-2xNbx)O3 (with x = 0.025, 0.05, 0.1, and 0.2) and Na0.5Bi0.5(NdyTi(1-2y)Nby)O3 (y = 0.0125, 0.025, and 0.05) ceramics were prepared through solid state sintering route. In the present study modulus resonance studies at high temperatures were carried out on the above ceramics. Higher piezoelectric performance in terms of parameters like thickness mode of electromechanical coupling factor and piezoelectric charge constant were observed for the ceramic compositions operating at higher temperature regime (798–873 K). In the case of ceramic composition with y = 0.0125, 0.025, and 0.05, the piezoelectric charge constant operating at 798K are 26.16 nm.V−1, 17.74 nm.V−1, and 24.33 nm.V−1, respectively.

Research progress in rare earth doping photoluminescent ferroelectric thin films

Rare earth doping is an important method to improve the properties of optoelectronic functional materials. Combining rare earth doping ferroelectric materials and rare earth photoluminescence can create new functional properties of ferroelectric materials. For example, choosing and using an appropriate rare earth element to be doped into a bismuth titanate ferroelectric material, the bismuth titanate will exhibit good photoluminescent properties as well as ferroelectric properties. Recently, photoluminescence properties originating from rare earth ions in oxide ferroelectric materials have attracted much attention for possible integrated photoluminescent ferroelectric device applications. In this paper, we briefly review the research status and progress of photoluminescence in rare earth photoluminescent ferroelectric materials, and we place the emphasis on our own research work in photoluminescent ferroelectric thin films such as (Bi,Eu)<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub>, (Bi,Er)<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub>, and codoped bismuth titanate thin films, and nanocomposite (Bi,Eu)<sub>4</sub>Ti<sub>3</sub>O<sub>12</sub> ferroelectric thin films. Our results show that the rare earth doped bismuth titanate ferroelectric thin films exhibit good photoluminescent and ferroelectric properties due to unique compositions and layered perovskite structure, that the Eu<sup>3+</sup> fluorescent structure probe can provide a new path for further studying the relationship between structure and property of Eu-doped ferroelectric thin films, that the rare earth photoluminescence can be used to examine the existence of morphotropic phase boundary in certain ferroelectric thin films such as Pr-doped <i>x</i>(K<sub>1/2</sub>Bi<sub>1/2</sub>)TiO<sub>3</sub>-(1－<i>x</i>)(Na<sub>1/2</sub>Bi<sub>1/2</sub>)TiO<sub>3</sub> thin films, and nanocomposite materials of ZnO nanomaterials, and that Au nanoparticles, Ag nanoparticles with Eu-doped bismuth titanate exhibit obviously enhanced photoluminescent properties.

Hydrothermal Synthesis of Sodium Bismuth Titanate Ferroelectrics

We have studied phase formation processes during sodium bismuth titanate, Na0.5Bi0.5TiO3 (NBT), synthesis under hydrothermal conditions at a temperature of 230°C for 24 and 48 h using stoichiometric mixtures of titanium oxide and bismuth hydroxide and NaOH solutions in the concentration range 5–30 M. The results demonstrate that, at sodium hydroxide concentrations in the range ≤10 M, there is almost no reaction between the starting reagents. In the concentration range 10–15 M, two-phase products are formed, containing a perovskite-like phase and the Bi12TiO20 bismuth titanate. Single-phase samples with the perovskite structure are formed at NaOH concentrations from 18 to 20 M, but their composition differs considerably from the stoichiometric one (Na0.61–0.69Bi0.39–0.31TiO2.89–2.81δ0.11–0.19, where δ stands for an oxygen vacancy). In the NaOH concentration range 22–30 M, first partial and then complete Bi3+ dissolution occurs. Increasing the synthesis time helps to stabilize the perovskite phase. The single-phase NBT ceramics have resistivity of 1.3 × 109 Ω cm, dielectric permittivity e/e0 = 360, dielectric loss tangent tan δ = 0.15, longitudinal electromechanical coupling coefficient Kp = 0.068, piezoelectric charge coefficients –d31 = 6.7 pC/N and d33 = 9 pC/N, and piezoelectric voltage coefficients –g31 = 2.07 mV m/N and g33 = 2.84 mV m/N. The relatively low piezoelectric performance of the ceramics is obviously due to the imperfect structure of the synthesized phases.

Acoustic instrumentation of the new generation of MTR: effect of nuclear radiation on modified Bismuth Titanate piezoelectric elements

In this article we present a first part of the results obtained during an irradiation campaign conducted at the Jozef Stefan Institute to observe the behaviour of piezoelectric materials under gamma and neutron flux. Specific instrumentation has been developed and has enabled the monitoring throughout the irradiation of several materials such as lead zirconate titanate (PZT) or modified Bismuth Titanate (BiT) in either massive or thick film form. Various parameters such as resonance frequency, electromechanical coupling coefficient, electrical capacitance, dielectric losses were measured as a function of the flow and dose received. The results obtained confirm that the samples work up to doses of 10 18 n°/cm2 and that the behaviour of the samples varies according to their composition and form.

Grain size effect on piezoelectric performance in perovskite-based piezoceramics

Piezoelectric ceramics is a versatile functional material that can realize interconversion between electrical energy and mechanical energy. As the electrical properties of piezoelectric ceramics are extremely sensitive to the grain size variation, the investigation of grain size effect has attracted much attention. In this paper, the recent research progress of the grain size effect on perovskite piezoelectric ceramics, including barium titanate (BT), lead zirconate titanate (PZT), potassium sodium niobate (KNN), and sodium bismuth titanate (BNT), is comprehensively reviewed. We especially focus on topics including feasible ways of fabricating piezoelectric ceramics with the desired grain sizes, the influence of the grain size effect on piezoelectric properties, and the corresponding physical mechanisms. This review would be beneficial to understanding the influence of the grain size effect on piezoelectric properties. The review concludes with the prediction of the further investigation on the grain size effect.

Research progress of pyroelectric characteristics of lead-free ferroelectric ceramics for infrared detection

Due to the excellent pyroelectric properties, ferroelectric ceramics containing lead element are widely used as sensitive materials in pyroelectric infrared detectors at present. The research and development of lead-free ferroelectric ceramics for this kind of detector has become a hot research spot in the areas of dielectric physics and materials in recent years. In this article, the recent research progress of the pyroelectric effect in series of important lead-free ferroelectric ceramic systems is reviewed, including barium titanate, sodium bismuth titanate, potassium sodium niobite, barium strontium niobite, etc. The methods of enhancing the pyroelectric effect are summarized, including doping modification, phase boundary design, process improvement, etc. Through comparative analysis of the relationship between pyroelectric properties and depolarization temperatures of different systems, it is concluded that bismuth sodium titanate based ceramics are the most potential lead-free materials in the future. The prospective research work of lead-free ferroelectric ceramics for infrared detection is also suggested.

Significantly enhanced energy storage performance of flexible composites using sodium bismuth titanate based lead-free fillers

A new lead-free antiferroelectric ceramic NBT–SBT was introduced into PVDF polymer to fabricate composites films, achieving record-high energy density of 15.3 J cm−3 at 500 MV m−1 and meeting the requirement of miniaturization and lightweight device.

Ultrahigh Energy Storage Properties in (Sr0.7Bi0.2)TiO3-Bi(Mg0.5Zr0.5)O3 Lead-Free Ceramics and Potential for High-Temperature Capacitors.

Due to the enhanced demand for numerous electrical energy storage applications, including applications at elevated temperatures, dielectric capacitors with optimized energy storage properties have attracted extensive attention. In this study, a series of lead-free strontium bismuth titanate based relaxor ferroelectric ceramics have been successfully synthesized by high temperature solid-state reaction. The ultrahigh recoverable energy storage density of 4.2 J/cm3 under 380 kV/cm, with the high efficiency of 88%, was obtained in the sample with x = 0.06. Of particular importance is that this ceramic composition exhibits excellent energy storage performance over a wide work temperature up to 150 °C, with strong fatigue endurance and fast discharge speed. All these merits demonstrate the studied ceramic system is a potential candidate for high-temperature capacitors as energy storage devices.

Optical and dielectric properties of Bi2Ti2O7/Bi4Ti3O12 nanocomposite

Bismuth titanate pure pyrochlore phase Bi2Ti2O7 (BT2) and its nanocomposite Bi2Ti2O7/Bi4Ti3O12 (BT2/BT4) are synthesized using the coprecipitation method at optimum reaction parameters. XRD results reveal the formation of pyrochlore cubic single phase in BT2 while a mixed-phase consisting of pyrochlore cubic and perovskite Aurivillius orthorhombic phase (Bi4Ti3O12) in BT2/BT4. The nanocomposite sample BT2/BT4 shows the smaller crystallite size (∼30 nm) and larger microstrain than BT2 nanoparticles. The average particle size is calculated using FESEM micrographs are ∼40 nm and ∼60 nm in BT2/BT4 and BT2 samples respectively. The presence of only Bi, Ti and O elements in both samples are confirmed by the EDX spectrum. FTIR spectra of BT2/BT4 confirms the vibrations corresponding to perovskite octahedral in additions to pyrochlore metal oxide vibrations. An optical band gap of nanocomposite BT2/BT4 is much smaller (1.65 eV) than pure phase BT2 sample (2.33 eV). Dielectric analysis reveals high dielectric constant and large a.c. conductivity in BT2/BT4 than the BT2 sample. The tuned optical and dielectric properties of BT2/BT4 nanocomposite shows that this nanocomposite can be further used in photovoltaic applications and as a photocatalyst for solar water splitting or organic waste degradation reactions.

From insulator to oxide-ion conductor by a synergistic effect from defect chemistry and microstructure: acceptor-doped Bi-excess sodium bismuth titanate Na0.5Bi0.51TiO3.015

Low levels of acceptor-type dopants can introduce appreciable levels of oxide-ion conductivity into NB0.51T due to a synergistic effect from defect chemistry and ceramic microstructure.

Non-ohmic conduction in sodium bismuth titanate: the influence of oxide-ion conduction.

A nominal Bi-excess starting composition of sodium bismuth titanate, Na0.5Bi0.51TiO3.015 (NB0.51T) produces dielectric ceramics that exhibit mixed n-type and oxide-ion conductivity with an ionic transport number of ∼0.1 at ≥600 °C. The bulk electrical conductivity, σb, of NB0.51T ceramics under a dc bias field of ≤100 V cm-1 has been investigated by impedance spectroscopy. Over the temperature range ∼550 to 750 °C, σb increases by up to one order of magnitude under the dc bias and returns to its initial value on removal of the bias. The enhancement of conductivity is dependent on temperature, atmosphere, dc bias field and the electrode materials. A maximum conductivity enhancement of >2000% is achieved at 600 °C in nitrogen using Pt electrodes. This is in contrast to that observed for other n-type perovskite titanates and oxygen-deficient rutile where σb is suppressed under a dc bias. This 'unusual' non-ohmic behaviour is attributed mainly to the influence of highly mobile oxygen vacancies in NB0.51T. The field-enhanced σb is best described to be a consequence of increased pumping of oxygen from the cathode to the anode, in which the electrode reactions play an important role. In addition, dissociation of defect clusters may also contribute to the enhanced σb under a dc bias. The high, fast and reversible response to the dc bias voltage may expand the potential application of NBT-based materials to memory devices.

Synthesis and Characterization of Lead Free Calcium Bismuth Titanate (Ca0.25Bi0.5 TiO3) Piezoelectric Ceramics

Bismuth layer-structured piezoelectric (BLSP) calcium bismuth titanate (Ca0.25Bi0.5TiO3) piezoelectric ceramics have been prepared via a conventional sol gel reaction method by mixing the desired chemicals in stoichiometric amounts. Calcium bismuth titanate (CBT) samples were characterized by means of XRD, SEM and FTIR spectroscopy. X-ray diffraction (XRD) analysis revealed that CBT ceramics exhibit a single phase orthorhombic structure. The SEM images confirm its morphological size ranging from 1.00 to 2.75µm.FTIR analysis reveals that calcium bismuth titanate has been prepared successfully. The photocatalytic removal of Methylene Blue, cadmium (Cd2+) and other toxic heavy metals will be carried out using CBT materials.

Synthesis and Characterization of Lead Free Calcium Bismuth Titanate (Ca0.25Bi0.5 TiO3) Piezoelectric Ceramics

Bismuth layer-structured piezoelectric (BLSP) calcium bismuth titanate (Ca0.25Bi0.5TiO3) piezoelectric ceramics have been prepared via a conventional sol gel reaction method by mixing the desired chemicals in stoichiometric amounts. Calcium bismuth titanate (CBT) samples were characterized by means of XRD, SEM and FTIR spectroscopy. X-ray diffraction (XRD) analysis revealed that CBT ceramics exhibit a single phase orthorhombic structure. The SEM images confirm its morphological size ranging from 1.00 to 2.75µm.FTIR analysis reveals that calcium bismuth titanate has been prepared successfully. The photocatalytic removal of Methylene Blue, cadmium (Cd2+) and other toxic heavy metals will be carried out using CBT materials.

Synthesis and Characterization of Lead Free Calcium Bismuth Titanate (Ca0.25Bi0.5 TiO3) Piezoelectric Ceramics

Bismuth layer-structured piezoelectric (BLSP) calcium bismuth titanate (Ca0.25Bi0.5TiO3) piezoelectric ceramics have been prepared via a conventional sol gel reaction method by mixing the desired chemicals in stoichiometric amounts. Calcium bismuth titanate (CBT) samples were characterized by means of XRD, SEM and FTIR spectroscopy. X-ray diffraction (XRD) analysis revealed that CBT ceramics exhibit a single phase orthorhombic structure. The SEM images confirm its morphological size ranging from 1.00 to 2.75 µm. FTIR analysis reveals that calcium bismuth titanate has been prepared successfully, and the ratio of calcium, bismuth and titania was found to be 0.25:0.50:1.00, respectively. The photocatalytic removal of Methylene Blue, cadmium (Cd2+) and other toxic heavy metals will be carried out using CBT materials.

Effect of fuel composition and concentration on dielectric properties of bismuth titanate (Bi4Ti3O12) synthesized by microwave-induced combustion method

In this work, ferroelectric bismuth titanate was prepared by a microwave-assisted auto-combustion method using different fuel agents (glycine, acetylacetone, and urea). X-ray diffraction patterns show that bismuth titanate with perovskite structure has been formed successfully in all cases. Although bismuth oxide as a major impurity is also identified, its quantitative amount has been minimized when glycine used as fuel in the combustion reaction. The effects of glycine concentration (fuel-deficient, stoichiometric, and fuel-rich) on the properties also have been evaluated. The results show that the degree of crystallinity increases when the fuel-rich reaction was used. Dielectric properties were measured as a function of frequency by means of an LCR meter. It is found that both parts of permittivity decrease with increasing frequency; conversely, AC conductivity rises with frequency. Furthermore, one semicircle is detected in the impedance spectra, demonstrating a significant contribution of the grain boundary. It is also observed that the higher the molar value of glycine, the greater the value of dielectric constant and the lower level of impurity.