Ferroelectric and piezoelectric properties of bismuth titanate thin films grown on different bottom electrodes by soft chemical solution and microwave annealing

Bismuth titanate (Bi4Ti3O12, BIT) films were evaluated for use as lead-free piezoelectric thin films in micro-electromechanical systems. The films were grown by the polymeric precursor method on LaNiO3/SiO2/Si (1 0 0) (LNO), RuO2/SiO2/Si (1 0 0) (RuO2) and Pt/Ti/SiO2/Si (1 0 0) (Pt) bottom electrodes in a microwave furnace at 700 degrees C for 10 min. The domain structure was investigated by piezoresponse force microscopy (PFM). Although the converse piezoelectric coefficient, d(33), regardless of bottom electrode is around (similar to 40 pm/V), those over RuO2 and LNO exhibit better ferroelectric properties, higher remanent polarization (15 and 10 mu C/cm(2)), lower drive voltages (2.6 and 1.3 V) and are fatigue-free. The experimental results demonstrated that the combination of the polymeric precursor method assisted with a microwave furnace is a promising technique to obtain films with good qualities for applications in ferroelectric and piezoelectric devices. (c) 2006 Elsevier Ltd. All rights reserved.

Ferroelectric ceramic/polymer composite for measuring X-ray intensity in the ortovoltage range

Pyroelectric sensors work as a thermal transducer converting the non-quantified thermal flux into the output measurable quantity of electrical charge, voltage or current. Ferroelectric ceramics and ferroelectric polymers have been extensively used as thermal detectors. More recently the research in the field of pyroelectricity has been concentrated on discovering materials with higher figures of merit (FOM), which means better sensing materials. Composite materials obtained with ferroelectric ceramics embedded in polymer host have received great attention because of their formability, mechanical resistance and the possibility to change their dielectric property varying the volume fraction of ceramic particles. In this work composite films made of modified lead titanate (PZ34) and poly(ether-ether-ketone) (PEEK) were characterized and used as sensing element to measure X-ray intensity in the ortovoltage range (120 - 300 kVp). The sensor response varies from 2.70 V to 0.80 V in the energy fluency range of 6.30 to 37.20 W/m(2). Furthermore the absorbed energy was analyzed as a function of the ionizing energy. The results indicate that the PZ34/PEEK composite with 60/40 vol.% can be useful to monitor X-ray radiation therapy.

Microstructural and ferroelectric properties of PbZr1-xTi(x)O(3) thin films prepared by the polymeric precursor method

The polymeric precursor method was employed in the preparation of PZT thin films on Pt(111)Ti/SiO2/Si(100) substrates. X-ray diffraction patterns revealed the polycrystalline nature of the PZT (53:47) thin films, which had a granular structure and a grain size of approximately 70 nm. A 350-nm thick film was obtained by running three cycles of the dip-coating/heating process. Atomic force microscopy (AFM) analyses showed the surface of these thin films to be smooth, dense and crack-free with low surface roughness (= 2.0 nm). The PZT (53:47) thin films annealed at 700 degreesC showed a well-saturated hysteresis loop. The C-V curves of perovskite thin film displayed normal ferroelectric behavior, while the remanent polarization (2P(r)) and coercive field (E-e) of the film deposited and measured at room temperature were 40 muC/cm(2) and 110 kV/cm, respectively. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Structural and ferroelectric properties of Pb1-xSrxTiO3 thin films

Strontium-modified lead titanate (PST) thin films with composition Pb1-xSrxTiO3 (0.10 < x &LE; 0.60) were grown on Pt/Ti/SiO2/Si substrates using a soft chemical process. The crystallization of the PST thin films was achieved by heat treatment at 600&DEG;C. The structural and microstructural modifications in the films were studied using X-ray diffraction (XRD) and atomic force microscopy, respectively. The XRD study shows that the lattice parameters of polycrystalline PST thin films calculated from X-ray data indicate a decrease in lattice tetragonality with the increase in strontium content in these films. This indicates a gradual change from tetragonal to cubic structure. By atomic force microscopy analysis, the average grain size of the thin films was systematically reduced with the increase in Sr content. The dielectric property of the thin films was found to be strongly dependent on the Sr concentration. With 60 at.% Sr content, a ferroelectric to paraelectric phase transition was observed at room temperature.

The effect of Nb doping on ferroelectric properties of PZT thin films prepared from polymeric precursors

Pure and Nb doped PbZr0.4Ti0.603 thin films was prepared by the polymeric precursor method and deposited by spin coating on Pt/Ti/SiO2/Si (100) substrates and annealed at 700 degreesC. The films are oriented in (1 1 0) and (1 0 0) direction. The electric properties of PZT thin films show strong dependence of the crystallographic orientation. The P-E hysteresis loops for the thin film with composition PbZr0.39Ti0.6Nb0.103 showed good saturation, with values for coercive field (E-c) equal to 60 KV cm(-1) and for remanent polarization (P-r) equal to 20 muC cm(-2). The measured dielectric constant (epsilon) is 1084 for this film. These results show good potential for application in FERAM. (C) 2004 Elsevier B.V. All rights reserved.

Influence of temperature on the dielectric and ferroelectric properties of bismuth titanate thin films obtained by the polymeric precursor method

The (1 1 7) and (0 0 1 0)-oriented Bi4Ti3O12 thin films were fabricated on Pt/Ti/SiO2/Si substrates by using a polymeric precursor solution under appropriate crystallization conditions. Atomic force microscopy and scanning electron microscopy showed relatively large grains, which is typical for this system. The capacitance dependence on voltage is strongly non-linear, confirming the ferroelectric properties of the films resulting from the domain switching. The (1 1 7)-oriented films exhibited a higher remanent polarization (23.7 μ C cm(-2)) than the (0 0 1 0)-oriented films (11.8 μ C cm(-2)). Fatigue tests revealed that the temperature of thermal treatment and degree of orientation affect the performance of the device. © 2005 Elsevier B.V. All rights reserved.

Synthesis, ferroelectric and optical properties of (Pb,Ca)TiO3 thin films by soft solution processing

Calcium modified lead titanate sol was synthesized using a soft solution processing, the so-called polymeric precursor method. In soft chemistry method, soluble precursors such as lead acetate trihydrate, calcium carbonate and titanium isopropoxide, as starting materials, were mixed in aqueous solution. Pb0.7Ca0.3TiO3 thin films were deposited on platinum-coated silicon and quartz substrates by means of the spinning technique. The surface morphology and crystal structure, dielectric and optical properties of the thin films were investigated. The electrical measurements were conducted on metal-ferroelectric-metal (MFM) capacitors. The typical measured small signal dielectric constant and dissipation factor at a frequency of 100 kHz were 299 and 0.065, respectively, for a thin film with 230 nm thickness annealed at 600degreesC for 2 h. The remanent polarization (2P(r)) and coercive field (E-c) were 32 muC/cm(2) and 100 kV/cm, respectively. Transmission spectra were recorded and from them, refractive index, extinction coefficient, and band gap energy were calculated. Thin films exhibited good optical transmissivity, and had optical direct transitions. The present study confirms the validity of the DiDomenico model for the interband transition, with a single electronic oscillator at 6.858 eV. The optical dispersion behavior of PCT thin film was found to fit well the Sellmeir dispersion equation. The band gap energy of the thin film, annealed at 600degreesC, was 3.56 eV. The results confirmed that soft solution processing provides an inexpensive and environmentally friendly route for the preparation of PCT thin films.

Structure, microstructure, ferroelectric/electromechanical properties and retention characteristics of [Bi1-x Nb (x) ]FeO3 thin films

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Piezoelectric effect in composite polyurethane-ferroelectric ceramics

Flexible and free-standing films of piezoelectric composites made up of lead zirconate titanate (PZT) ceramic powder dispersed in a castor oil-based polyurethane (PU) matrix were obtained by spin coating and characterized as materials for sensor applications. The piezoelectric coefficients d 31 and d 33 were measured with the usual technique. The piezoelectric charge constant d 33 yields values up to ≤24 pC/N, even at lower PZT content (33 vol%). Some desirable properties like piezoelectricity, flexibility and good mechanical resistance show this new material to be a good alternative for use as sensors and actuators.

Temperature and stoichiometry effect on microstructural and ferroelectric properties of Pb(Zr1-xTix)O3 thin films prepared by chemical soulution deposition

Lead zirconate titanate (PZT) solutions were prepared using a polymeric precursor method, Zr n-propoxide and Ti i-propoxide were used as starting materials with ethylene glycol and water as solvents. The PZT solution was spin-coated on Pt/Ti/SiO2/Si substrates, baked on a hot plate, and finally heat-treated in a tube furnace between 400 and 800°C. The surface morphology and grain size of the films were characterized by atomic force microscopy (AFM), using a tapping mode with amplitude modulation. The films, thermal annealed at temperatures higher than 500°C, exhibited a dense microstructure, without noticeable cracks or voids. Electrical properties were investigated as a function of composition and annealing temperature.

Diffuse Effect of the Tungsten Doped Ba(Zr0.10Ti0.90)O3 Ferroelectric Ceramics

Barium zirconate titanate Ba(Ti0.90Zr0.10)O3 ceramics doped with WO3 (BZT:2W) have been prepared by a traditional solid phase reaction. The effect of temperature on the structural and electrical properties was investigated. X ray diffraction data evidenced formation of secondary phases for the samples sintered at 1300oC end 1350oC while the pure phase was attained at 1200oC. A modified Curie-Weiss law was used to describe the diffuseness of a phase transition. As temperature increases, the maximum dielectric permittivity decreased. The fine-grained sample showed a 'diffuse-like' ferroelectric behavior. The dielectric permittivity reaches a maximum value (εm ~6420 at 10 kHz) for the ceramics sintered at 1200oC for 4 hours.

Dielectric and structural characterization of Pb1-xAxZr0.40Ti0.60O3 (A = Sr, Ca) ferroelectric ceramics

This paper reports the influence of Sr- and Ca-substitution on the structural and ferroelectric properties of Pb1-xSrxZr0.40Ti0.60O3 (PSZT) and Pb1-xCaxZr0.40Ti0.60O3 (PCZT) ceramic systems. The dielectric measurements show that these substitutions cause a diffuse behavior in the dielectric permittivity curves for all samples. According to the X-ray absorption near-edge structure (XANES) spectra collected at Ti K- and LIII-edge, when Pb was replaced by Sr or Ca, a decrease in the local distortion around Ti atoms in the TiO6 octahedron could be observed. The O K-edge XANES spectra also revealed that the hybridization between O 2p and Pb 6sp states decreased as the amount of Sr or Ca atoms increased. Based on these results, it was possible to ascertain that the ferroelectric behavior in PSZT and PCZT samples bears a close correlation to the hybridization weakening between O 2p and Pb 6 sp states. © 2013 by American Scientific Publishers.