TiO3 Thick Films Research Articles

Dielectric properties and energy storage performance of lead-free strontium calcium titanate (Sr0.60Ca0.40)TiO3 thick films

Dielectric properties and energy storage performance of lead-free strontium calcium titanate (Sr0.60Ca0.40)TiO3 thick films

Free‐standing 0.9Na0.5Bi0.5TiO3‐0.1Sr0.7Bi0.2TiO3thick films produced by water‐based tape‐casting method

Abstract(1‐x)Na0.5Bi0.5TiO3‐xSr1‐1.5yBiyTiO3solid solutions attract increased interest as lead‐free ferroelectrics perspective for sensors, actuators, and energy storage applications. However, thick films of this composition are of great demand, as they could serve as a good compromise between the bulk ceramics and thin films—due to the advantage in realization of miniaturized devices without reducing the power and sensitivity of target devices, as in the case of thin films, and ability to accommodate application of much higher electric fields compared to bulk ceramics. In the present research, for the first time, we have produced free‐standing 0.9Na0.5Bi0.5TiO3‐0.1Sr0.7Bi0.2TiO3thick films by water‐based tape‐casting method, using just two organic chemicals, which is an eco‐friendly production approach having only several successful attempts in the case of ferroelectric materials before. We conducted a detailed study focusing on development of microstructure at various sintering temperatures and consequences of evaporation of Bi during the production. Our findings show how the choice of the sintering temperature can help in improvement of density of the thick films, reaching 98.9%, and changing the grain size. It is demonstrated that a secondary phase appears predominantly on the free surface of the films. We propose a method for effective minimization of its formation—by the choice of appropriate embedding powder media during the sintering.

Intense Pulsed Light Thermal Treatment of Pb(Zr,Ti)O3 /Metglas Heterostructured Films Resulting in Extreme Magnetoelectric Coupling of over 20Vcm-1 Oe-1.

Magnetoelectric (ME) film composites consisting of piezoelectric and magnetostrictive materials are promising candidates for application in magnetic field sensors, energy harvesters, and ME antennas. Conventionally, high-temperature annealing is required to crystallize piezoelectric films, restricting the use of heat-sensitive magnetostrictive substrates that enhance ME coupling. Herein, a synergetic approach is demonstrated for fabricating ME film composites that combines aerosol deposition and instantaneous thermal treatment based on intense pulsed light (IPL) radiation to form piezoelectric Pb(Zr,Ti)O3 (PZT) thick films on an amorphous Metglas substrate. IPL rapidly anneals PZT films within a few milliseconds without damaging the underlying Metglas. To optimize the IPL irradiation conditions, the temperature distribution inside the PZT/Metglas film is determined using transient photothermal computational simulation. The PZT/Metglas films are annealed using different IPL pulse durations to determine the structure-property relationship. IPL treatment results in an enhanced crystallinity of the PZT, thus improving the dielectric, piezoelectric, and ME properties of the composite films. An ultrahigh off-resonance ME coupling (≈20Vcm-1 Oe-1 ) is obtained for the PZT/Metglas film that is IPL annealed at a pulse width of 0.75ms (an order of magnitude higher than that reported for other ME films), confirming the potential for next-generation, miniaturized, and high-performance ME devices.

Flexible (Ba0.7Sr0.3)TiO3 thick films with mechanically stable dielectric tunability

Flexible (Ba0.7Sr0.3)TiO3 thick films with mechanically stable dielectric tunability

High-performance screen-printed Au/Ba0.85Sr0.15TiO3/Pt capacitors for tunable devices

Metal-Ferroelectric-Metal capacitor structure, employing the lead free ferroelectric Ba0.85Sr0.15TiO3 thick films are successfully prepared by screen printing process on silicon platinized Pt/Ti/SiO2/Si substrates. The surface morphology and microstructure are analyzed by scanning electron microscope and X-ray diffraction. The thick film showed a well adhesion to the Pt/Ti/SiO2/Si substrate and uniform thickness of about ~ 20 µm. The frequency dependence of dielectric characteristics of BST thick films is systematically discussed and compared in a large temperature range. Ferroelectric characterizations, tunability and leakage current in the Au/BST(thick film)/Pt capacitor were also studied at room temperature by polarization cycles (P–V), Capacitance (C–V) and current (I–V) measurements. The high tunability (81%) combined with the low dielectric loss tangent and low leakage current makes Ba0.85Sr0.15TiO3 thick films one of the encouraging candidates for various modern electronic tunable devices.

Low-temperature sintering and electrical properties of Ba0.68Sr0.32TiO3 thick films

Ba0.68Sr0.32TiO3 (BST) thick films were prepared by screen printing on a flexible fluorophlogopite substrate. In order to realise the co-firing of the BST film with a silver electrode at a lower temperature, the BST precursor was used as a solvent for the screen-printing slurry and the cold sintering technique was used to pretreat the film. The sintering temperature of BST thick films prepared by conventional sintering process was higher than 1200 °C. When sintered at 950 °C, the thick films exhibited a high porosity. The density of the thick films was significantly improved after pretreatment with the cold sintering process (CSP). After the cold-sintered thick films were sintered at 950 °C for 30 min and then fired with a silver electrode, the samples exhibited a relative dielectric constant of 773 (at 25 °C and 10 kHz), a dielectric loss of 0.025, a remanent polarization of 5.3 μC/cm2, and a coercive field strength of 38.1 kV/cm. Therefore, the low-temperature co-firing of BST thick films with a silver electrode was successfully realised.

A facile and cost-effective approach for the fabrication Bi0.5Na0.5TiO3 thick films on flexible substrate for energy storage capacitor applications

The current research reports a facile and cost-effective technique for the deposition of functional ceramics Bi0.5Na0.5TiO3 thick films on flexible, low cost, electrically integrateable Ni substrate by using electrophoretic deposition (EPD) technique. EPD is a well-known, eco-friendly process for depositing coatings on a conductive substrate from a colloidal suspension. A reliable approach was adopted for stable colloidal suspension of BNT particles during conventional solid-state synthesis process by using high energy ball milling in acetone medium without the complications of surfactants and expensive platinum substrate. BNT films with thickness ranging from ~55 to 165 μm were successfully obtained by exploring EPD parameters i.e. voltage from 100 to 125 V and coating time from 30 to 240 s. Thick coatings with comparatively better adhesiveness were deposited at 100 and 125 V with coating time up to 90 s. Thick films were densified by sintering at 1150 °C for 30 min. Phase analysis were conducted by using X-Ray diffraction (XRD), Fourier transformed infrared spectroscopy and Raman spectroscopy. XRD analysis revealed the formation of single (111) peak indicating the pure perovskite structure of BNT thick film. Scanning electron microscope studies indicated that dense and uniform microstructure was obtained by EPD coating with the film thickness of ~93 μm. Impedance spectroscopy confirmed two electrically active regions of grain interior and grain boundaries.

Investigation of Ba0.6Sr0.4TiO3 thick films by means of a novel THz-TDS approach

Ba0.6Sr0.4TiO3 (BST) ferroelectric thick films were grown on MgO(0 0 1) and Al2O3(0 0 0 1) single-crystal substrates by using a pulsed laser deposition method. Structural, morphological, optical, and terahertz characterization of the BST films were performed by X-ray Diffraction, Atomic Force Microscopy, Spectroscopic Ellipsometry (SE), and Terahertz Time-Domain Spectroscopy (THz-TDS). Single-phase samples with strong preferred (1 1 1) orientation and surface roughness lower than 1.5% of their thicknesses have been obtained for both types of substrates. SE was employed to extract the thickness and optical properties by using a 3-layer optical model (substrate/thin film/roughness). The inferred refractive index @630 nm is around 2.05, while the optical interference is visible until 3.3 eV. The THz-TDS measurements in transmission set-up were carried out one after the other on substrates before and after the BST film deposition. The standard THz-TDS analysis of double-layer samples proved difficult to complete in the cases in which a thin or thick film is deposited on a much thicker substrate of known dielectric properties. However, we have been able to extract the complex dielectric permittivity in the THz domain for BST samples with thicknesses of few microns, by developing a specific procedure of data analysis.

High tunability in lead-free Ba0.85Sr0.15TiO3thick films for microwave tunable applications

Lead free ferroelectric Ba0.85Sr0.15TiO3(BST) thick films were successfully deposited by screen printing process on Ag–Pd/Al2O3 substrates. The microstructure of the samples was analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The thick films showed a good adhesion to the Ag–Pd/Al2O3 substrate, a porous microstructure and uniform thicknessesof about 10 μm. The dielectric properties of BST thick films were studied over a wide frequency range (10-1 Hz to 106 Hz) and in a large temperature range from 25 °C to 350 °C. The AC conductivity in BST thick films was systematically investigated. Ferroelectric characterizations and tunability were also studied at room temperature by polarization cycles P(E) and capacitance C(E) measurements. The high values of dielectric permittivity and tunability (67%) combined with low dielectric loss (tgδ) make Ba0.85Sr0.15TiO3 thick films one of the encouraging candidates for microwave tunable applications.

Improvement of Energy Storage Characteristics of (Ba0.7Ca0.3)TiO3 Thick Films by the Increase of Electric Breakdown Strength from Nano-Sized Grains

Lead free (Ba0.7Ca0.3) TiO3 thick films with nano-sized grains are prepared using an aerosol deposition (AD) method at room temperature. The crystallinity of the AD thick films is enhanced by a post annealing process. Contrary to the sharp phase transition of bulk ceramics that has been reported, AD films show broad phase transition behaviors due to the nanosized grains. The polarization-electric hysteresis loop of annealed AD film shows ferroelectric behaviors. With an increase in annealing temperature, the saturation polarization increases because of an increase in crystallinity. However, the remnant polarization and cohesive field are not affected by the annealing temperature. BCT AD thick films annealed at 700 °C/2h have an energy density of 1.84 J/cm3 and a charge-discharge efficiency of 69.9%, which is much higher than those of bulk ceramic with the same composition. The higher energy storage properties are likely due to the increase in the breakdown field from a large number of grain boundaries of nano-sized grains.

Low temperature sintering and nonlinear dielectric properties of lithium-doped Ba0.6Sr0.4TiO3 thick films prepared by tape-casting

The thick films with nominal composition of Ba0.6Sr0.4TiO3+0.4 wt% Li2O were prepared through tape casting. The structure and nonlinear dielectric properties of the resulting thick films were investigated within the sintering temperature range of 1050–1100 °C. The thick film specimens sintered at the relatively low temperatures exihibited dense and no crack microstructure due to the addition of sintering aid Li2O and modified process technology. An obvious influence of sintering temperature on the microstructure and nonlinear dielectric properties was detected. The discrepancy in nonlinear dielectric properties among the specimens sintered at different temperatures was qualitatively interpreted in terms of interfacial charge accumulation and defect dipole reorientation. Sintering at 1080 °C was determined to be preferred for the specimens with regard to the nonlinear dielectric properties. At room temperature, the specimen attained a dielectric constant of 3050 and a relatively low dielectric loss tangent of 0.15% at 10 kHz together with a extremely large figure of merits (FOM) of 580 and a tunability of 88% at 10 kHz and 200 kV/cm.

Enhanced Self-Biased Magnetoelectric Coupling in Laser-Annealed Pb(Zr,Ti)O3 Thick Film Deposited on Ni Foil.

Enhanced and self-biased magnetoelectric (ME) coupling is demonstrated in a laminate heterostructure comprising 4 μm-thick Pb(Zr,Ti)O3 (PZT) film deposited on 50 μm-thick flexible nickel (Ni) foil. A unique fabrication approach, combining room temperature deposition of PZT film by granule spray in vacuum (GSV) process and localized thermal treatment of the film by laser radiation, is utilized. This approach addresses the challenges in integrating ceramic films on metal substrates, which is often limited by the interfacial chemical reactions occurring at high processing temperatures. Laser-induced crystallinity improvement in the PZT thick film led to enhanced dielectric, ferroelectric, and magnetoelectric properties of the PZT/Ni composite. A high self-biased ME response on the order of 3.15 V/cm·Oe was obtained from the laser-annealed PZT/Ni film heterostructure. This value corresponds to a ∼2000% increment from the ME response (0.16 V/cm·Oe) measured from the as-deposited PZT/Ni sample. This result is also one of the highest reported values among similar ME composite systems. The tunability of self-biased ME coupling in PZT/Ni composite has been found to be related to the demagnetization field in Ni, strain mismatch between PZT and Ni, and flexural moment of the laminate structure. The phase-field model provides quantitative insight into these factors and illustrates their contributions toward the observed self-biased ME response. The results present a viable pathway toward designing and integrating ME components for a new generation of miniaturized tunable electronic devices.

Effects of Fe3+ doping on electrical properties and energy-storage performances of the (Na0.85K0.15)0.5Bi0.5TiO3 thick films prepared by sol-gel method

The immense potential of dielectric capacitor for use in energy-storage applications has propelled much recent research and development. Here, we prepared a kind of lead-free ferroelectric thick films of Fe-doped (Na0.85K0.15)0.5Bi0.5TiO3 (NKBT-Fex, x = 0, 0.01, 0.02 and 0.04). The effects of Fe3+ contents on the microstructure, dielectric properties and energy-storage performances of NKBT thick films were studied in detail. The studies on complex impedance spectroscopic were also carried out for NKBT-Fe0.02 thick film at different temperature from 100 Hz to 1 MHz. By Fe doping, the leakage current of the NKBT-Fex thick films was greatly reduced, while the breakdown strength (BDS) and the difference between the maximum polarization and remanent polarization were enhanced. These characteristics lead to excellent energy-storage performances with good temperature and frequency stability. In particular, a maximum energy-storage density (W) of 33.3 J/cm3 with an efficiency (η) of 51.3% was achieved in the NKBT-Fe0.02 thick film. These results open up a promising feasible route to enhance the energy-storage performances by properly element doping.

Effects of Mn doping on dielectric properties and energy-storage performance of Na0.5Bi0.5TiO3 thick films

Lead-free Na0.5Bi0.5Ti1−xMnxO3 (NBTMnx, x=0, 0.01, 0.03 and 0.05) ferroelectric thick films have been fabricated on LaNiO3/Si(100) substrate by using a polyvinylpyrrolidone-modified sol-gel method and the effects of Mn content on their microstructure, dielectric properties and energy-storage performance were investigated. Compared with the pure Na0.5Bi0.5TiO3 (NBT) thick films, NBTMnx thick films exhibited a large enhancement in dielectric properties and energy-storage performance. Particularly, a giant recoverable energy-storage density (W) of 30.2J/cm3 and the corresponding efficiency (η) of 47.7% were obtained in NBTMn0.01 thick film at 2310kV/cm. Moreover, the NBTMn0.01 thick film displayed good energy-storage stability over a large temperature range at different frequency.

Effects of thickness on switching current for (Pb 0.97 La 0.02 )(Zr 0.95 Ti 0.05 )O 3 antiferroelectric films under thermo‐electric coupled field

Homogeneous and compact antiferroelectric (AFE) (Pb, La)(Zr, Ti)O3 thick films in large area with different thicknesses were successfully fabricated by the sol–gel processing on Pt(111)/Ti/SiO2/Si(100) substrates. The characteristics of switching current of samples with different thicknesses under thermo-electric coupled field were investigated in detail. The experimental result shows that the peak of switching current density increased with the increase of temperature in three samples. Moreover, it is found that the thickness of the films has a big effect on the current density. Therefore, the peak of switching current density increased with increasing in the thickness at the same temperatures. The maximum switching current density of film with the thickness of 2254 nm is 4.35 × 10−5A/cm2. These results are quite important and necessary for design and preparation of the AFE materials applied on high sensitivity and intelligent micro-sensors and micro-actuators.

Ba0.6Sr0.4TiO3 thick film derived by polymer modified MOSD route for tunable microstrip antenna applications

ABSTRACTFrequency and phase agile microstrip antenna applications require relatively thick Barium Strontium Titanate (BST) films for good tunability. In this work, Polymer (PEG-200) modified MOSD process route is developed to produce cracks free (Ba0.6, Sr0.4) TiO3 Thick film on Low loss ST-X quartz substrate. Structural and electrical characteristics of the deposited films were investigated using Atomic Force Microscope, X-Ray Diffraction, C-V and C-F characterizations. XRD characterization conformed the single BST phase with polycrystalline nature of the film. AFM analysis depicted equiaxed shaped grains with average grain size and roughness of 120 nm and 4.15 nm respectively. Dielectric tunability, dielectric constant and loss tangent of the deposited films were 36.46%, 310 and 0.0213 respectively at 1 MHz frequency using MIM capacitive structure where conductive oxide LNO was used as bottom electrode. The applicability of polymer modified BST thick films over low loss substrate as composite substrate for tunable microstrip antenna applications at microwave frequency was demonstrated by design, fabrication and testing of a compact frequency tunable microstrip antenna in coplanar configuration. The tunability exhibited at X band frequency proves the suitability of developed processed route for tunable antenna applications.

Large-displacement actuating and high-frequency vibrating characteristics of silicon-based antiferroelectric (Pb, La)(Zr, Ti)O3 thick-film micro-cantilevers

Five micro-cantilevers in different length and width but the same thickness were fabricated with the antiferroelectric (Pb, La)(Zr, Ti)O3 thick film, and show superior actuation behaviors (33μm for the maximum displacement) and high vibration characteristics (107.11kHz for the greatest frequency) owing to the high displacement caused by the phase transition. At first, the vibration characteristics were verified. With the micro-cantilever length varying from 400μm to 650μm, the vibrating displacement and velocity both increased, while the response frequency decreased. Next, the antiferroelectricity was tested and the results indicate all of 5 micro-cantilevers have typical antiferroelectric properties with double hysteresis loop square-like. As a result, these testing results can help micro-actuators with a key driving technology of micro-miniature, rapid response speed and large displacement.

High dielectric tunability of Ba(Zr0.2Ti0.8)O3–(Ba0.7Ca0.3)TiO3 thick films modified by a solution-immersion process

High-quality lead-free 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 thick films with the thickness of 8μm were prepared by screen printing with a solution-immersion process. The solution-modified films near the morphotropic phase boundary (MPB) showed very dense and homogenous microstructure with large grain size, and exhibited moderate dielectric constant of 1680 and low dielectric loss of 1.38% at 10kHz with 0V bias at room temperature. High dielectric tunability up to 76.7% at 12kV/mm and 10kHz was achieved in the modified films. The excellent dielectric properties associated with good microstructure and MPB composition, make the lead-free films be a promising candidate for dielectric tunable capacitor applications.

Out-of-plane actuation of silicon micro-cantilever based on (Pb, La) (Zr, Ti)O3 antiferroelectric thick films

With micro-machining technologies, the micro-cantilevers of Si-based antiferroelectric (Pb, La) (Zr, Ti)O3 thick films were fabricated, and five sizes of cantilevers were completed in one chip. Out-of-plane motion of the cantilever structure was described with the out-of-plane actuation method. Under the square wave excited by the voltage of 42 ± 2 V, the micro-cantilevers presented the good performance, such as high vibration velocity of 0.93 m/s and big cantilever tip displacement of 31 μm due to the electrical field induced phase transition in the thick film. The drive voltage as the phase-transition voltage was applied to the antiferroelectric material layers for the out-of-plane motions measured by Micro System Analyzer (MSA-400), and hence the 1st-order resonance frequency of the cantilevers was 40.08 kHz. These results reveal that the antiferroelectric thick films (Pb, La) (Zr, Ti)O3 are of characteristics of large electrostrictive strain and show the potential and board application for the micro-devices with those films in micro-actuators and high-speed digital switches.

Constrained sintering and electrical properties of BNT–BKT lead-free piezoceramic thick films

Bi0.5(Na0.82K0.18)0.5TiO3 (BNKT) thick films were prepared by screen-printing on the alumina substrate. Grain growth behavior, constrained sintering processing, dielectric properties, ferroelectric properties and piezoelectric properties were studied. The results show that BNKT thick films exhibit a much lower grain growth rate and smaller grain size than bulk samples due to the constrained sintering on rigid substrates. The XRD measurement revealed that the residual tensile stress formed during sintering resulting from the constrained in-plane shrinking. The typical 80μm thick films demonstrate the relative dielectric constant of 775, dielectric loss of 3.6% at 1kHz, remnant polarization of 18.6μC/cm2, coercive field of 61kV/cm, and longitudinal effective piezoelectric coefficient, d33 of 105pm/V at room temperature. Compared with BNT-based piezoelectric bulk ceramics, the smaller longitudinal piezoelectric coefficient is related to the clamping effect of the substrate and the limited extrinsic piezoelectric contributions due to the reduced non-180° domain wall motions.