Effects of preferred orientation on the piezoelectric properties of Pt/Pb(Zr0.3Ti0.7)O3/Pt thin films grown by sol–gel process

Tetragonal lead zirconate titanate (PZT) films with different orientations and 200 nm film thicknesses were prepared on platinized silicon substrates. Types of substrate and control of thermal processes, such as layer-by-layer and one-crystallization heat treatments, result in highly (111) or (100)-oriented PZT films. The piezoelectric, dielectric, and ferroelectric properties of polycrystalline PZT films have been investigated as a function of preferred orientation. The property difference between (111) and (100)-oriented films appears to be induced by the effect of ferroelastic domain existence (90° domain in tetragonal composition). From a modified phenomenological equation, the higher electrostrictive coefficient value of 5.6 × 10⁻² m⁴/C² for (100)-oriented PZT may be responsible for the larger piezoelectric coefficients in (100)-oriented polycrystalline PZT films of 44 pm/V in comparison to (111)-oriented PZT films with about 3.1 × 10⁻² m⁴/C² of Q ₃₃ and 40 pm/V of d _33,f . It was also observed that two (100)-oriented films prepared by different heat treatments showed different values in piezoelectric, dielectric, and ferroelectric properties even though only (100) orientation was characterized for both cases. This process-induced difference may also play an important role in determining both intrinsic and extrinsic contribution to the properties, even though these parameters seem to be more responsible for extrinsic components, such as domain wall motion.     

Magnetoelectric properties of Ba0.8Sr0.2TiO3–CoFe2O4 multilayered composite film via sol–gel method

Ba_0.8Sr_0.2TiO₃–CoFe₂O₄ (BST–CFO) multilayered composite films were prepared on Pt/Ti/SiO₂/Si substrates via a sol–gel method and spin-coating technique. Microstructures, electric property, magnetic property and magnetoelectric (ME) property of the composites were studied. Results show that the composite films calcined at 750 °C have BST and CFO phases and no obvious impurity phases were detected. Further, the composite films exhibit layered structures and a transition layer which is composed of interfacial delamination exists at the interface between BST and CFO layers. Ferroelectric and ferromagnetic properties were simultaneously observed in the films, evidencing the coexistence of the ferroelectric and ferromagnetic properties. Furthermore, the saturation magnetization value of the composite film is lower than that of the pure CFO film derived by the same processing as a result of the effect of the nonferromagnetic BST layers. Also, ferroelectric hysteresis loops reveal that the saturated polarization and remanent polarization of the composite film are lower than those of the pure BST films. In addition, the composite film exhibits a strong ME effect, which makes the composite film attractive for technological applications as devices.     

Fabrication and electrical properties of textured Ba(Zr0.2Ti0.8)O3–(Ba0.7Ca0.3)TiO3 ceramics using plate-like BaTiO3 particles as templates

Plate-like BaTiO₃ (BT) particles were used as templates to fabricate grain-oriented Ba(Zr_0.2Ti_0.8)O₃–(Ba_0.7Ca_0.3)TiO₃ (BZT–BCT) ceramics. The effects of the sintering temperature and the soaking time on the microstructure and electrical properties of the textured BZT–BCT ceramics were investigated. The results show that textured ceramics were obtained with orientation factor better than 0.5. The textured BZT–BCT ceramics have rhombohedral and tetragonal structures. Terrace morphology can be observed in the grains and the mechanism of grain growth is multi-nucleation multilayer growth. The T_R–T and T_C of BZT–BCT ceramics shift to higher temperature as the soaking time increases. Textured structures improve the dielectric, piezoelectric properties, and weaken the dielectric relaxor characteristics. When BZT–BCT ceramics sintered at 1,500 °C for 20 h, the maximum piezoelectric coefficient of 350 pC/N can be obtained.     

Orientation-dependent microwave dielectric properties of Ba0.6Sr0.4TiO3 thin films prepared by sol–gel method

Barium strontium titanate (Ba_0.6Sr_0.4TiO₃, BST) thin films have been prepared on the (100) LaAlO₃ single-crystal substrates by sol–gel technique. The X-ray diffraction study indicated that the thin films exhibited (100) preferred orientation and random orientation depending upon the concentration of precursor solution. The nonlinear dielectric properties of the BST films were measured using an interdigital capacitor. The temperature dependence of dielectric constant of the BST thin films was measured at 1 MHz in the temperature range from ?100 to 80 °C. The Curie temperature T _c of the films derived from 0.1, 0.2 and 0.3 M was found to be ?18.5, ?32.5 and ?39.9 °C, respectively. The tunability of BST films with the (100) preferred orientation was 30.74 %, which was much higher than that of thin films with random orientation at the frequency of 10 kHz with an applied electric field of 80 kV/cm. The microwave dielectric properties of the BST thin films were measured by a vector network analyser from 1 to 10 GHz.     

Studies on magnetic and magnetoelectric properties of the NiFe2O4–Ba0.7Sr0.3TiO3 composites

The magnetic and magnetoelectric properties of magnetoelectric (ME) composites consisting of with nickel ferrite (NiFe₂O₄) and barium strontium titanate (Ba_0.7Sr_0.3TiO₃) were investigated. The composites were prepared by standard double sintering ceramic method. The X-ray diffraction analysis was carried out to confirm the phases formed during sintering and also to calculate the lattice parameters. The hysteresis measurements were done to determine saturation magnetization (M_s), remenance magnetization (M_r) and coercivity (H_c) of the samples. The magnetoelectric voltage coefficient (dE/dH)_H was studied as a function of intensity of the magnetic field. The measured magnetoelectric (ME) response demonstrated strong dependence on the volume fraction of NiFe₂O₄ and the applied magnetic field. A large ME voltage coefficient of about 560 μVcm⁻¹Oe⁻¹ was observed for 15% NiFe₂O₄ + 85% Ba_0.7Sr_0.3TiO₃ composite.     

Microstructure and dielectric relaxor behavior of Ba(Zr0.2Ti0.8)O3–(Ba0.7Ca0.3)TiO3–BaBi4Ti4O15 ceramics by tape casting

Plate-like BaBi₄Ti₄O₁₅ powders were used to fabricate 0.952[Ba(Zr_0.2Ti_0.8)O₃–(Ba_0.7Ca_0.3)TiO₃]–0.048BaBi₄Ti₄O₁₅(abbr. BZCT-BBT) ceramics by tape casting. The microstructure and dielectric relaxor behaviors of BZCT-BBT ceramics were investigated. BZCT-BBT ceramics can be sintered well at 1,100?°C and mainly consisted of tetragonal perovskite phase and BaBi₄Ti₄O₁₅ (abbr. BBT) phase. The lattice constants decrease as the sintering temperature increases due to substitution of Bi³⁺ for the A-site atoms of the perovskite structure. There is no obvious difference between the structure in the perpendicular and parallel directions, however, an evident difference of dielectric properties in the two directions is observed. Comparing with Ba(Zr_0.2Ti_0.8)O₃–(Ba_0.7Ca_0.3)TiO₃(abbr. BZCT) ceramics, BZCT-BBT ceramics show obvious relaxor characteristics which are evidenced by the degree of diffuseness γ calculated using the modified Curie–Weiss law. Meanwhile, the addition of BBT decreases T_m, which results from the decrease of grain size. The reduction of ε_m is mainly caused by phase structure deviation from the coexisting rhombohedral and tetragonal structure to single tetragonal.     

Ba(Zr0.3Ti0.7)O3 doping to enhance the dielectric and energy discharging performances of a 0.65Bi0.5Na0.5TiO3–0.35Sr0.7Bi0.2TiO3 lead-free ceramic

Journal of Materials Science: Materials in Electronics - A group of lead-free (1 ? x)(0.65Bi0.5Na0.5TiO3–0.35Sr0.7Bi0.2TiO3)–x[Ba(Zr0.3Ti0.7) O3]...     

Damping properties of epoxy-based composite embedded with sol–gel-derived Pb(Zr 0.53 Ti 0.47 )O 3 thin film with different thicknesses

Pb(Zr $_{\mathbf{0\boldsymbol{\cdot}53}}$ Ti $_{\mathbf{0\boldsymbol{\cdot}47}})$ O ₃ (PZT) thin films were prepared on Pt/Ti/SiO ₂ /Si substrate by sol?Cgel method. The effect of film thickness on microstructure, ferroelectric and dielectric properties was investigated. The single-phase PZT films were obtained with different thicknesses. PZT films with a thickness of 190?C440?nm had better dielectric and ferroelectric properties. The epoxy/PZT film/epoxy sandwiched composites were prepared. The thickness of PZT films influenced their damping properties of the composites, and the epoxy-based composites embedded with 310?nm-thick PZT films had the largest damping loss factor of 0 $\boldsymbol{\cdot} $ 915.     

Low temperature synthesis of Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 nanopowders by solution based auto combustion method

Ba(Zr_0.2Ti_0.8)O₃–0.5(Ba_0.7Ca_0.3)TiO₃ (BZT–BCT) nanopowders were synthesized by citrate–nitrate auto combustion method using TiO₂ as a source of titanium. The formation mechanism, phase evolution and particle size were investigated using thermal analysis, Fourier transform infra-red spectroscopy, X-ray diffraction, Raman spectroscopy and transmission electron microscope. The molar ratio of metal, citric acid and ethylene diamine tetraacetic acid was kept at 1:1.5:0.1 and pH ~ 9, to get a uniform and complete combustion. Perovskite BZT–BCT was formed in the as-burnt state (280 °C), though calcination at 700 °C is required to remove a small amount of impurities, which is significantly lower than the solid state reaction method. The particle size of BZT–BCT powder was in the range of 40–70 nm.     

Structural and dielectric relaxor properties of A-site deficient samarium-doped (Ba1−x Sm2x/3)(Zr0.3Ti0.7O3) ceramics

Rare earth samarium (Sm)-doped barium zirconate titanate (Ba_1?x Sm_2x/3)(Zr_0.3Ti_0.7)O₃ (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10) ceramics were prepared using solid state reaction (SSR) route. The structural and microstructural characterizations of the materials were done by using X-ray diffraction and SEM analysis, respectively. Rietveld refinement technique employed to investigate the details of crystal structure revealed single-phase cubic perovskite structure belonging to space group Pm-3m. Microstructure of the doped ceramics were found to be porous and of irregular shape and size along with aggregative characteristic. FTIR technique was employed to study the influence of additives in ceramics compositions and to investigate the displacement of M–O bonds. Raman spectroscopic study revealed that the substitution of Ba²⁺ ions by Sm³⁺ ions shifted the Raman-active modes toward higher energy, which indicated that these materials undergo an increase in average cubicity with increase in Sm³⁺ ion concentration. The temperature dependence of dielectric properties was investigated in the frequency range from 1 kHz to 1 MHz. The dielectric measurement indicated a diffuse type of phase transition (DPT). The broadening in the dielectric permittivity and frequency dependence behavior with increase in frequency indicated a relaxor behavior of these materials. The relaxation strength of these materials was well adjusted by using the Vogel–Fulcher relation.     

Structural properties of Pb(Zr0.53Ti0.47)O3/YBa2Cu3O7-δ heterostructures on SrTiO3 substrates

The structures of ferroelectric Pb(Zr0.53Ti0.47)O3 and high-Tc YBa2Cu3O7– superconductor integrated films on (0 0 1) SrTiO3 substrate prepared by the r.f./d.c. magnetron sputtering method have been studied by X-ray grazing incidence reflectivity, diffuse scattering and high-resolution X-ray diffraction methods combined with atomic force microscopy (AFM) and SEM techniques. The results of high-resolution X-ray diffraction show that the quality of Pb(Zr0.53Ti0.47)O3 improved as the thickness increased. On the other hand, the crystalline quality of YBa2Cu3O7– deteriorated and the superconducting transition temperature, Tc, decreased as the thickness of Pb(Zr0.53Ti0.47)O3 increased. The strain state was similar for different thickness samples and the lattice mismatch strain in the Pb(Zr0.53Ti0.47)O3 layer was almost totally relaxed. The root mean square (r.m.s.) roughness at Pb(Zr0.53Ti0.47) O3/YBa2Cu3O7– interface was determined to be about 1.7±0.3 nm by X-ray specular reflectivity. The r.m.s. roughness at the surface of Pb(Zr0.53Ti0.47)O3/YBa2Cu3O7– bilayer samples was about 1.5 to 2.0±0.3 nm which was larger than that of YBa2Cu3O7– single-layer sample measured by both X-ray specular reflectivity and AFM methods. The results from AFM and SEM show that the morphological characteristics of the Pb(Zr0.53Ti0.47)O3 layer surface were large grains covering about 10% in area distributed on a fine-grained matrix. © 1998 Chapman & Hall     

Dielectric properties of Fe-doped TiO2 nanoparticles synthesised by sol–gel route

Fe-doped nanocrystalline samples of titanium oxide have been synthesised by sol–gel route and conventional sintering process at 450°C under atmospheric conditions. These samples are characterised by X-ray diffraction (XRD), X-ray photoelectron spectroscopy, transmission electron microscopy (TEM) and dielectric property measurement. Samples with Fe content more than 4?mole% crystallises in rutile phase and those with less than 4?mole% crystallises in anatase phase. Nanocrystallite size has been controlled by Fe doping. Crystallite size was found to decrease with Fe concentration in the anatase phase samples whereas reverse happens in rutile phase samples of titanium oxide. There is a slight variation in numerical values of crystallite sizes measured by the two techniques: TEM and XRD peak broadening. The highest crystallite size was 86?nm in 10?mole% Fe-doped samples and the lowest 20?nm in 4?mole% Fe-doped sample. Large dispersions and anomalous values of the dielectric constant, εr were observed at low frequency in anatase phase samples. Rutile phase samples exhibit little dispersion over the measurement frequency range of 20?Hz to 10?MHz. The dielectric constant value of all the samples stabilises to a constant value at higher frequencies. This value is dependent on the final crystalline phase but independent of the crystallite size. The anomalous dielectric behaviour of anatase samples at low frequencies is assigned to the adsorbed –OH ions on the sample surface.     

Fabrication,characterization and sensing properties of Cu(II) ion imprinted sol–gel thin film on QCM

Cu(II)-molecularly imprinted sol–gel films (Cu(II)-MISGF), coated on a quartz crystal microbalance (QCM) chip, were fabricated using a sol–gel procedure. Co-hydrolysis and co-condensation of Cu(II) (templates), 3-aminopropyltrimethoxysilane (APTS, functional monomer) and tetraethoxysilane (TEOS, cross-linking agent) were performed with acid and base catalysis. The properties of the Cu(II)-MISGF were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and the electrochemical methods of cyclic voltammetry (CV). Microstructural observations revealed that the acid-catalyzed system yielded more mechanically stable thin films. A combined Cu(II)-MISGF-QCM with flow injection analysis (FIA) method was utilized to investigate the sensing performance of the Cu(II)-MISGF, with special emphasis on the most important properties of sensitivity, selectivity and response time. The Cu(II)-MISGF-QCM sensor, at a TEOS/APTS molar ratio of 10, exhibited excellent selectivity and rapidly responded to Cu(II) ions.     

Dielectric enhancement of BaTiO3/BaSrTiO3/SrTiO3 multilayer thin films deposited on Pt/Ti/SiO2/Si substrates by sol–gel method

Polycrystalline BaTiO₃/Ba_0.6Sr_0.4TiO₃/SrTiO₃ (BT/BST/ST) multilayer thin films with different periodicities have been deposited on Pt/Ti/SiO₂/Si substrates by using a sol–gel method. The multilayer thin films were crack free, compact and crystallized in a perovskite structure. The dielectric constant of the multilayer thin films was significantly increased and the dielectric loss was almost the same as those of uniform BT, ST and BST thin films. The dielectric constant increased with increasing stacking periodicity as the thickness of each individual layer decreased. The multilayer thin films showed excellent dielectric properties and can be promisingly used for the dielectric layer of silicon-based embedded capacitors in package substrate.     

The preparation and properties of CeO2–TiO2 film by sol–gel spin-coating process

Ultraviolet absorbing CeO₂–TiO₂ coatings were prepared by the sol–gel spin-coating process heat treated at 500 °C. The films obtained were brilliant yellow, adherent and had some pattern on the soda-lime glass substrate. The optical transmittance, thickness and hardness of the films as a function of the number of coatings, aging time (0, 24, 48, 96 h) or aging temperature (28, 35, 40, 50 °C) were determined, and surface microstructure of the films was observed by SEM. We found some pattern on the surface of films. This pattern was similar to that of the stage for fixing the substrate. The pattern on the surface of films would be caused by the difference of thermal conductivity to slide glass in the part of metal of the stage and hollow part of the stage.     

Dielectric properties of La/Zr codoped Ba0.67Sr0.33TiO3 ceramics prepared from citrate–nitrate combustion derived powders

La/Zr codoped Ba_0.67Sr_0.33TiO₃ (BST) ceramics were fabricated via citrate–nitrate combustion derived powders, and the microstructure and dielectric properties of BST ceramics were investigated. All ceramic samples show a pure perovskite structure. The dielectric constant and loss decrease with increasing Zr content. The additions effectively suppress the grain growth of BST ceramics. It is found that the temperature-permittivity characteristics for codoped BST ceramics could be controlled using various doping content.     

Thickness-dependent electrical properties of sol–gel derived Pb(Zr0.52Ti0.48)O3 thick films using PbTiO3 buffer layers

Pb(Zr_0.52Ti_0.48)O₃ (PZT) thick films, with thickness up to 4 μm, using PbTiO₃ (PT) buffer layers were successfully prepared on silicon-based substrates by a sol–gel method. Thermal analysis (thermogravimetric–differential thermal analysis) of PT and PZT sols were used to determine the pyrolysis and annealing temperatures. X-ray diffraction results show that the PZT/PT composite thick films possess perovskite structure and the dominant crystalline orientation changes from (100) to (110) with increasing the film thickness. Furthermore, the composite thick films exhibit thickness-dependent ferroelectric and dielectric properties, i.e., the coercive field decreases while dielectric constant increases as the thickness increases. Theoretical analysis shows that the thickness-dependent electrical properties are mainly attributed to the low dielectric constant of PT buffer layer and the relaxation of internal stress in PZT films.