Sr0.5Ba0.5Nb2O6 Research Articles

Engineering Heterostructured Piezoelectric Nanorods with Rich Oxygen Vacancy‐Mediated Piezoelectricity for Ultrasound‐Triggered Piezocatalytic Cancer Therapy

AbstractUsing piezoelectric bionanomaterials to promote the generation of reactive oxygen species (ROS) is being increasingly recognized in ultrasound (US)‐triggered tumor treatments. The mechanism underlying this innovative treatment involves US irradiation, which activates the built‐in electric field (BIEF) and induces energy‐band bending in piezoelectric materials (PEMs). In this study, Sr0.5Ba0.5Nb2O6 (SBN) nanorods (NRs) are synthesized using a molten salt method. Subsequently, oxygen‐vacancy (OV)‐rich SBN/Sr2Nb2O7 (SBN/SNO) heterojunction nanocomposites (NCs) are fabricated via H2 annealing of the SBN NRs. The engineering strategy focused on enhancing ROS generation, thereby augmenting the piezoelectric catalytic activity of the NCs. This configuration ensures that the BIEF and heterojunction‐induced field act synergistically to provide a sustained driving force for the separation of electron‐hole (e−‐h+) pairs. Importantly, the OVs on the surfaces of the H2‐annealed SBN NRs create electron‐rich sites, which substantially enhance their piezocatalytic capabilities. In vitro and in vivo analyses of hepatocellular carcinoma (HCC) models demonstrate the significant cytotoxic and tumor‐inhibitory capabilities of this rich OV‐mediated sonopiezoelectric therapy (SPT) and illustrate its potential as a promising therapeutic approach against cancer.

Remarkably Boosting Piezocatalytic Performance of Sr0.5Ba0.5Nb2O6 Piezoceramics via Size Optimization and Oxygen Vacancy Engineering

AbstractPiezocatalysis is capable of harnessing mechanical energy for environmental remediation, which is regarded as a green and promising technology to be exploited. Piezoceramics are struggling to be used as highly efficient piezocatalysts due to their grain size reaching tens of micrometers usually. Herein, a feasible and straightforward method is proposed to turn piezoceramic powders into highly efficient piezocatalysts by integrating size optimization and oxygen vacancy modulation. This strategy is validated by treating lead‐free Sr0.5Ba0.5Nb2O6 (SBN) piezoceramic powders with high‐energy ball‐milling (hBM). The rate constant k value of 46.95 × 10−3 min−1 for rhodamine B (RhB) piezocatalytic degradation of SBN‐hBM‐12h is almost 18 times higher than that of pristine SBN. Besides, the SBN‐hBM‐12 h catalyst performed superior antibacterial properties against Escherichia coli. The enhanced piezocatalytic efficiency is attributed to the introduced abundant oxygen vacancies absorbing and activating O2 into reactive oxygen species. Well‐modulated oxygen vacancy concentration can effectively accelerate the generation and separation of free carriers. However, the excess oxygen vacancies in SBN render the weakened piezoresponse thus suppressing the piezocatalytic activity. This study elucidates the critical role of oxygen vacancies in piezocatalysis and provides insights into the development of efficient piezocatalysts.

Different effect of Li+, Na+, K+ -doping on crystal structure and electrical property of Sr0.6Ba0.4Nb2O6

Ferroelectric Sr0.6Ba0.4Nb2O6 (SBN) shows typical unfilled tetragonal tungsten bronze structure where 1/6 A sites and all C sites are unoccupied. The presence of such structural vacancy provides the possibility to further modulate the crystal structure and electrical properties. In this work, alkali ions (Li+, Na+, K+) doped SBN ceramics have been fabricated via solid-solution reaction method. In general, each doping promotes the crystal structure evolves from unfilled toward filled tungsten bronze. However, the different doping ion radius causes the differences in occupying initial structural vacancies, resulting in significantly different electrical properties, Li+ doping enhances relaxor characteristic whereas Na+ and K+ doping lead to normal ferroelectric behavior, accompanying an increase in Curie temperature (TC) from 36 °C of SBN to 40, 212, 148 °C of Li+, Na+ and K+ doping, respectively. Benefiting from improved relaxor degree and high density, the Li+ doped SBN displays a good energy storage performance. Since the ratio of Sr/Ba and (Sr + Ba)/Nb has not been changed, this work presents direct evidence for the effect of structural vacancy on crystal structure and properties, as well as inspiration for further work on unfilled tungsten bronze.

Enhanced Tunable Properties of Strontium Barium Niobate Films on Dielectric Alumina Substrate at Microwaves

(Sr,Ba)Nb2O6 (SBN) relaxor ferroelectric thin films exhibiting nonlinear properties promising for microwave applications were grown on a polycrystalline aluminum oxide substrate for the first time. Films of good crystallinity were obtained using the sputtering technique and high-temperature annealing. For all films, a significant change in the phase composition after high-temperature treatment was observed, and annealing provided a different effect on the phase composition of films deposited at different substrate temperatures. Tunable properties of the SBN films were investigated as a function of the deposition temperature and annealing conditions using planar capacitors with microwaves. The capacitor based on the strontium barium niobate film deposited at a temperature of 950 °C and subjected to annealing demonstrates a tunability of 44% and a loss tangent of 0.009 ÷ 0.022, which is expressed in the microwave commutation quality factor of 1740. This is the first successful attempt to form planar capacitive structures based on SBN films, which reveal a commutation quality factor above 1000 for tunable microwave applications.

Resistive switching in tetragonal tungsten bronze Sr0.6Ba0.4Nb2O6 thin films and control of Schottky barrier by insertion of BiFeO3 layer

Tetragonal tungsten bronze Sr0.6Ba0.4Nb2O6 (SBNO) has exceptional electro-optical, piezoelectric, and thermoelectric properties. Its potential as an electronic device is, furthermore, also relay on the good insulation and multiple-channels structural. However, the transport behavior in SBNO films remains poorly researched. Here, a Pt/SBNO/LSMO capacitor was prepared using the magnetron sputtering method on STO (001) substrates, and its transport behavior was measured. Interestingly, an ultra-high resistive-switching ratio over 103 was obtained in SBNO film. The read voltage when the switch ratio is ∼103 drops from 2 V to 0.5 V by inserting a BFO-layer between the interface of SBNO and LSMO. The findings demonstrate that the interface barrier in SBNO/BFO/LSMO devices between the SBNO and BFO layers is essential for maintaining a high switching ratio at low voltage. As a result, the SBNO/BFO/LSMO demonstrates a method for reducing read voltage and offers an approach for future resistive-switching applications.

Electrocaloric effect of alkali co-substituted Sr0.6Ba0.4Nb2O6 ceramics

We have investigated the electrocaloric properties of K+ and Na+ co-substituted Sr0.6Ba0.4Nb2O6 (SBN) ceramics using the indirect method. Tetragonal tungsten bronze (K0.5Na0.5)2x(Sr0.6Ba0.4)5-xNb10O30 (KNSBN) with x = 0.24 was synthesized using dual-step sintering. Despite the low amount, K+ and Na+ co-substitution resulted in normal ferroelectric behaviour, showing no significant shift in the dielectric maximum temperature of 111 °C with increasing frequency. Maximum electrocaloric temperature change (ΔT) of 0.3 K was observed at an electric field of 30 kV/cm (ΔE) yielding the largest electrocaloric responsivity (ΔT/ΔE) among SBN based ceramics. This relatively large value is in agreement with the larger pyroelectric coefficient of KNSBN compared to SBN based ceramics.

Composition, Structure, and Dielectric Characteristics of (Sr0.5Ba0.5)Nb2O6/Pt(111)/Si(001) Films

Sr0.5Ba0.5Nb2O6 (SBN) relaxor ferroelectric films of different thicknesses have been grown on Pt(111)/Si(001) substrates by rf sputtering. We have studied their structure, composition–depth profiles, lattice dynamics, and dielectric properties at temperatures from 25 to 200°C. The results demonstrate that the composition of the films does not vary with depth and corresponds to that of the ceramic target used and that the SBN/Pt interface has a transition layer more than 30 nm in thickness, consisting of a mixture of platinum and SBN. According to X-ray diffraction characterization results, the films are polycrystalline, with a preferential orientation of the SBN [001] axis along the normal to the substrate surface. At a film thickness of 950 nm or above, the SBN films on Pt(111)/Si substrates differ insignificantly in unit-cell parameters, lattice dynamics, and Burns temperature from SBN single crystals. We discuss general relationships of structure formation and characteristics of the films.

Microstructures and energy storage properties of Sr0.5Ba0.5Nb2O6 ceramics with SrO–B2O3–SiO2 glass addition

The Sr0.5Ba0.5Nb2O6 (SBN) dielectric ceramics with different SrO–B2O3–SiO2 (SBS) glass content were prepared via solid state reaction method. The effect of glass content on their sintering temperature, density, microstructure, dielectric and energy storage properties was investigated. The addition of glass was confirmed to be effective in reducing sintering temperature and refining microstructure. The XRD results showed that no secondary phase was formed after adding glass, but Sr2+ might diffuse into SBN lattice during the thermal heat-treatment. The dielectric breakdown strength (BDS) of SBN ceramic was remarkably enhanced with 4 wt% glass addition, which is almost twice as much as that of pure SBN ceramic. This sample also presented a large discharge energy density of 0.55 J/cm3 and high energy efficiency of 72.4%. These results indicate the addition of SBS glass significantly improved the microstructures, dielectric and energy storage properties of SBN ceramics.

A study on SBN-POP composites for pyroelectric sensing applications

Pyroelectric performance of the composites of plaster of Paris (POP) and the lead-free Sr0.5Ba0.5Nb2O6 (SBN) ceramic have been studied in this paper. SBN-POP composites with 30, 40, 50, and 60% SBN content by weight referred as SBN30, SBN40, SBN50, and SBN60 have been studied. The dielectric constants for SBN30, SBN40, SBN50, and SBN60 composites are obtained as 10.51, 21.62, 43.61, and 57, respectively at room temperature (25 °C). The maximum open-circuit voltages in the range of 31 to 103 mV could be obtained by subjecting the SBN-POP composite samples to temperature gradient by blowing hot and cold air. Further maximum voltages in the range of 8 to 34 mV and maximum current in the range of 2.9 to 18 nA could be obtained across 1 MΩ resistance. The SBN-POP composites seem to be suitable candidate to be used as pyroelectric sensors.

Energy storage properties of Dy3+ doped Sr0.5Ba0.5Nb2O6 thick film with nano-size grains

We studied the temperature stable high-energy storage capacitors. Sr0.5Ba0.5Nb2O6 (SBN) is the lead-free ferroelectric solid solution between BaNb2O6 and SrNb2O6. By doping Dy into SBN, the Curie temperature was lowered and dielectric constant was increased. To improve the breakdown behavior of Dy-doped SBN, the aerosoldeposition(AD) was applied to fabricate the dense films with nano-sized grains. These nano-grain give a large number of grain boundaries, suppressing the electron conduction in ceramics. The dielectric constant and breakdown electric field of the AD films annealed at 650 °C were measured as 2307 and 9.9 MV/m, while bulk were 1080 and 4 MV/m. Energy density and efficiency of the AD films annealed at 650 °C were also enhanced as 0.65 J/cc and 90.2% and bulk were 0.08 J/cc and 72.1%, respectively. In addition, the dielectric constant of AD film annealed at 550 °C and 650 °C were quite stable up to 150 °C.

Microstructures and Energy Storage Properties of Sr0.5Ba0.5Nb2O6 Ceramics with BaO–B2O3–SiO2 Glass Addition

Sr0.5Ba0.5Nb2O6 (SBN) ceramics with the BaO–B2O3–SiO2 (BBS) glasses have been successfully produced for high energy-storage density capacitor applications. The phase evolution, microstructures, dielectric properties and energy storage properties of the SBN-based glass ceramics were investigated. X-ray diffraction analysis revealed all ceramic samples were of tetragonal tungsten bronze-type structures. As the mass ratio of glass in the glass ceramics increased from 0.1wt.% to 10 wt.%, the dielectric constant of the glass ceramics increased initially and then decreased with the increasing glass content. Compared to pure Sr0.5Ba0.5Nb2O6 ceramics, the glass ceramics with a small amount of BBS glass addition illustrated better energy storage properties. The glass-ceramic with 0.5wt. % BBS glass addition showed the highest breakdown strength of 194 kV/cm and a maximum energy storage density of 0.286 J/cm3.

Pyroelectric materials for solar energy harvesting: a comparative study

Pyroelectric solar energy harvesting has been a prominent area of research for the past few years. This study is an attempt to compare different pyroelectric materials for harvesting solar energy. Seven different pyroelectric materials including (NH2CH2COOH)3·H2SO4 (TGS), Sr0.5Ba0.5Nb2O6 (SBN), Ca0.2(Sr0.5Ba0.5)0.8Nb2O6 (CSBN), Pb(Zr0.5Ti0.5)O3 (PZT), polyvinylidene difluoride (PVDF), BaTiO3 and LiTaO3 were studied and compared using finite-element analysis. SBN was found to be the potential pyroelectric material with the maximum storage voltage of 11.47 V across an optimized load capacitance. SBN was subjected to further analysis, revealing an optimum power output of 4.9 μW at the optimized cycle frequency (0.040 Hz), a load resistance of 50 MΩ and a load capacitance of 4.7 μF, while the stored energy was found to be 576.87 μJ.

Dielectric, magnetoelectric and magnetodielectric properties in CMFO-SBN composites

The paper reports synthesis of Sr0.5Ba0.5Nb2O6 (SBN) and Co1.2−xMnxFe1.8O4 (CMFO) via ceramic and hydroxide co-precipitation routes respectively. The nanopowders of SBN-CMFO0.1 (MSBN0.1) and SBN-CMFO0.3 (MSBN0.3) are compacted to form the desired magnetoelectric (ME)/magnetodielectric (MD) composites. The Bi2O3 is used as a sintering aid. The Bi2O3 at three weight percent is observed to cause agglomeration of SBN and CMFO particles and improve the magneto-mechanical coupling. The composites are investigated for their ferroelectric, ferromagnetic, dielectric, magnetoelectric (ME) and magnetodielectric (MD) properties. The results on the magnetocapacitance (Mc) are observed interesting and could be correctly understood in terms of the stress induced variation in the dielectric constant. The MC is observed to remain fairly constant between 10 to 500kHz and possess a useful magnitude of Mc nearly 4%.

Magnetoelectric and magnetodielectric properties of SBN–CMFO nanocomposites

The paper reports synthesis of nanoparticles of Sr0.5Ba0.5Nb2O6 (SBN) and Co1.2−xMnxFe1.8O4 (CMFO) via ceramic and hydroxide co-precipitation routes, respectively. The nanopowders of SBN–CMFO0.1 (MSBN0.1) and SBN–CMFO0.3 (MSBN0.3) are compacted together to form the desired magnetoelectric/magnetodielectric (ME/MD) composites. The Bi2O3 is used as a sintering aid. The Bi2O3 at three weight percent is observed to cause agglomeration of SBN and CMFO particles and improve the magnetomechanical coupling. The paper reports synthesis, structural and morphological studies on the MSBN composites. The composites are investigated for their dielectric, ME and MD properties. The results on the magnetocapacitance (MC) are observed interesting and could be correctly understood in terms of the stress-induced variation in the dielectric constant. The MC is observed to remain fairly constant between 10 and 500 kHz and possess a useful magnitude of nearly 4 %.

Investigation on magnetoelectric and dielectric properties of Co0.9Mn0.3Fe1.8O4–Sr0.5Ba0.5Nb2O6 composites

The present paper reports the dielectric and magnetoelectric properties of Mn substituted yCo1.2−xMnxFe1.8O4 (CMFO) and (1 − y) Sr0.5Ba0.5Nb2O6 (SBN) ME composites. The composites are formed with three weight percent of Bi2O3 as sintering aid. The Co1.2−xMnxFe1.8O4 is initially studied for variation of electrical resistivity ρ, saturation magnetization Ms, permeability μ, coercive field Hc and coefficient of magnetostriction λ to determine a composition suitable to form a ME composite. Here x = 0.3 is observed to posses optimal value of ρ, Ms, μ, Hc and λ, therefore the composites are formed using Co0.9Mn0.3Fe1.8O4. The composites y MSBN = y CMFO + (1 − y) SBN are synthesized and investigated for their structural, dielectric and magnetoelectric properties. The dielectric constant of composites is observed to exhibit contribution due to interfacial polarization as well as a contribution due to the SBN phase. The variation of linear magnetoelectric coefficient α and quadratic magneto electric coefficient β for varies compositions are reported in this paper. The paper also repots the effect of sintering temperature and variation of frequency on the magnitude of α and β. It is observed that the use of sintering aid increases the magnetoelectric output of the MSBN composites. The samples with y = 0.4 is observed to show sufficiently large and useful magnitude of magnetoelectric coefficients.

The Influences of Rapid-Thermal Annealing on the Characteristics of Sr0.6Ba0.4Nb2O6 Thin Film

The Sr0.6Ba0.4Nb2O6 (SBN) thin films were successfully prepared on Pt/Ti/Si and SiO2/Si/Al substrates and crystallized subsequently using rapid thermal annealing (RTA) process in ambient atmosphere for 1 min. The surface morphologies and thicknesses of as-deposited and annealed SBN thin films were characterized by field emission scanning electron microscopy, and the thickness was about 246 nm. As compared with the as-deposited SBN thin films, the RTA-treated process had improved the crystalline structures and also had large influence on the crystalline orientation. When the annealing temperatures increased from 700 degrees C to 900 degrees C, the diffraction intensities of (410) and (001) peaks apparently increased. Annealed at 900 degrees C, the (001) peak had the maximum texture coefficient and SBN thin films showed a highly c-axis (001) orientation. The influences of different RTA-treated temperatures on the polarization-applied electric field (P-E) curves and the capacitance-voltage (C-V) curves were also investigated.

Effects of Deposition Parameters and Annealing Temperatures on the Characteristics of the Sr<sub>0.6</sub>Ba<sub>0.4</sub>Nb<sub>2</sub>O<sub>6</sub> Thin Films

Sr0.6Ba0.4Nb2O6 (SBN) thin films were prepared by radio frequency (RF) sputtering onto the SiO2/Si/Al and Pt/Ti/Si substrates to form the MFIS and MFM structures. Their deposition rates increased with decreasing oxygen concentration and with increasing RF power. Their optimal deposition parameters were the substrate temperature of 500°C, chamber pressure of 10 mTorr, oxygen concentration of 40%, and RF power of 120W, respectively. The rapid temperature annealing (RTA) process had large effects on the grain growth of the SBN thin films. The effects of different RTA temperatures on the leakage current density - electrical field curves and the capacitance - voltage curves of the SBN thin films were also investigated.

Effects of stress on the optical properties of epitaxial Nd-doped Sr0.5Ba0.5Nb2O6 films

Nd-doped Sr0.5Ba0.5Nb2O6 (SBN) thin films with thicknesses ranging from 15 nm to 460 nm were grown on MgO (100) substrates using pulsed laser deposition technique. X-ray diffraction studies showed that the films were highly (001)-oriented and epitaxially grown on the substrates. Raman spectroscopy revealed the presence of residual stresses in the films especially for those with thicknesses below 100 nm. Transmittance and photoluminescence spectra revealed that the band-gap energies as well as the light-induced emission bands were shifted to higher energies as the film thickness decreased. The Nd3+ emission lines in the films were also dependent on film thickness. Origins of these observations were discussed based upon the stress as well as grain size effects.

Nonlinear Optical Properties of Nanosized Rare-Earth–Doped Strontium Barium Niobate Ceramics

ABSTRACT Nanosized, undoped and rare-earth–doped Sr0.5Ba0.5Nb2O6 (SBN) ceramic systems were synthesized by an aqueous organic gel route. The precursor gel on calcinations at 800°C for 2 hr produces undoped and rare-earth–doped SBN systems of pure tungsten bronze lattice structure. These systems have been characterized for their structure by XRD, SEM, and TEM. The nonlinear absorption behavior of the undoped and rare-earth–doped SBN ceramic systems was investigated by use of the open-aperture Z-scan technique using 532 nm, 5 ns laser pulses. The authors found that these materials are potential optical limiters at this excitation wavelength.

Simultaneous characterization of the electro-optic, converse-piezoelectric, and electroabsorptive effects in epitaxial (Sr,Ba)Nb2O6 thin films

Implementation of the linear electro-optic (EO) effect in thin film waveguides is expected to allow drastic reductions in the drive voltage, power, and dimensions of devices devoted to light modulation. It should also enable the realization of electrically tunable photonic crystal devices. In this paper we introduce a method which eliminates systematically the sources of the unreliability which strongly affects thin film EO characterization. Based on a Fabry–Perot reflective configuration, the method enables characterizing simultaneously the EO, converse-piezoelectric, and electroabsorptive effects in a film. It provides the magnitude and sign of each of the involved coefficients, and allows accounting for the whole of experimental data versus angle of incidence for both transverse-electric and transverse-magnetic polarizations. At λ=633 nm and room temperature, the results obtained with an epitaxial strontium barium niobate (SrxBa1−xNb2O6, x=0.60) ferroelectric thin film, are: r13=+8.5±1.3 pm/V, r33=+38.9±0.5 pm/V, d33=Δe/ΔV=+21±4 pm/V, and Δko/ΔV=(+9.8±0.6)×10−6, where r13 and r33 are two linear EO coefficients, d33 is a converse-piezoelectric coefficient, and e, ko, V represent, respectively, the film thickness, film ordinary extinction coefficient, and applied voltage. Converse-piezoelectric and electroabsorptive effects are found significant in the film response at a frequency below piezoelectric resonance. Diagonal and effective EO coefficients of the (Sr,Ba)Nb2O6 (SBN) film explored in the present work are larger than those of a crystal of lithium niobate (LN) at the same wavelength λ=633 nm. Taking into account the significant difference in dielectric permittivity between the two materials, advances and potential of LN and SBN thin film paths are compared.