SYNTHESIS OF ULTRA-FINE CRYSTALLINE ZRXTI1-XO4 POWDER BY POLYMERIC PRECURSOR METHOD

Reactive ZrxTi1-xO4 (x=0.65, 0.50 and 0.35) powder was prepared by the polymeric precursor method. Studies by X-ray diffraction (XRD), nitrogen adsorption/desorption, and thermogravimetric analysis (TG) showed that powders with high crystallinity (>90%) and high surface areas (>40 m(2)/g) are obtained after calcination at 700 degrees C for 3 h. Infrared spectroscopy and XRD results showed that these titanates nucleate from the amorphous phase with no intermediate phases, at low temperature (450 degrees C).

Microstructure and dielectric properties of (Ba,Sr)TiO3 thin film produced by the polymeric precursor method

BaxSr1-xTiO3 (x = 0.6) (BST) thin films were successfully prepared on a Pt(111)/TiO2/SiO2/Si(100) substrate by spin coating, using the polymeric precursor method. BST films with a perovskite single phase were obtained after heat treatment at 700 degrees C. The multilayer BST thin films had a granular structure will a grain size of approximately 60 nm. A 480-nm-thick film was obtained by carrying out five cycles of the spin-coating/heating process. Scanning electron microscopy and atomic force microscopy analyses showed that the thin films had a smooth, dense, crack-free surface with low surface roughness (3.6 nm). At room temperature and at a frequency of 100 kHz, the dielectric constant and the dissipation factor were, respectively, 748 and 0.042. The high dielectric constant value was due to the high microstructural quality and chemical homogeneity of the thin films obtained by the polymeric precursor method.

Preparation and properties of ferroelectric Pb1-xCaxTiO3 thin films produced by the polymeric precursor method

Pb1- xCaxTiO3 thin films with x = 0.24 composition were prepared by the polymeric precursor method on Pt/Ti/SiO2/Si substrates. The surface morphology and crystal structure, and the ferroelectric and dielectric properties of the films were investigated. X-ray diffraction patterns of the films revealed their polycrystalline nature. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses showed the surface of these thin films to be smooth, dense and crack-free with low surface roughness. The multilayer Pb1-xCaxTO3 thin films were granular in structure with a grain size of approximately 60-70 nm. The dielectric constant and dissipation factor were, respectively, 174 and 0.04 at a 1 kHz frequency. The 600-nm thick film showed a current density leakage in the order of 10(-7) A/cm(2) in an electric field of about 51 kV/cm. The C-V characteristics of perovskite thin films showed normal ferroelectric behavior. The remanent polarization and coercive field for the deposited films were 15 muC/cm(2) and 150 kV/cm, respectively. (C) 2001 Kluwer Academic Publishers.

Synthesis and characterization of Li2ZnTi3O8 spinel using the modified polymeric precursor method

In this work we report the synthesis procedure, crystallographic, structural and magnetic properties of the Li2ZnTi3O8 spinel obtained using a modified polymeric precursor method. This synthesis method generates very reactive and property-controlled nanoparticles. The samples were characterized using X-ray powder diffraction (XRD) associated to the Rietveld refinement method, thermogravimetric analysis (TG), specific surface area, scanning electron microscopy (SEM) and magnetic susceptibility measurements.The phase formation temperature of the lithium zinc titanate spinel was observed to decrease due to the homogeneity and highly controlled nanometric particle size. (C) 2003 Elsevier B.V. All rights reserved.

Optical properties of potassium niobate thin films prepared by the polymeric precursor method

Thin films of potassium niobate were deposited on MgO (100) substrates by the polymeric precursor method and annealing in static air at 600 degreesC for 20 h. The obtained films were characterized by X-ray diffraction, atomic force microscopy (AFM) and the prism coupling method. The phi-scan diffraction evidenced the growth of the films with fourfold symmetry. AFM study shows that the films are homogeneous, dense and present a smooth surface. The refractive index and optical losses were strongly influenced by the degree of crystallinity. (C) 2004 Elsevier B.V. All rights reserved.

Influence of the solution pH on the morphological, structural and electrical properties of Bi3.50La0.50Ti3O12 thin films obtained by the polymeric precursor method

Lanthanum-doped Bi4Ti3O12 thin films (BLT) were deposited on Pt/Ti/SiO2/Si substrates using a polymeric precursor solution. The spin-coated films were specular, crack-free and crystalline after annealing at 700 degrees C for 2 h. Crystallinity and morphological evaluation were examined by X ray diffraction (YRD) and atomic force microscopy (AFM). The stability of the formed complex is of extreme importance for the formation of the perovskite phase. Films obtained from acid pH solution present elongated grains around 200 ran in size, whereas films obtained from basic solution present a dense microstructure with spherical grains (100 nm). The dielectric and ferroelectric properties of the BLT films are strongly affected by the solution pH. The hysteresis loops are fully saturated with a remnant polarization and coercive voltage of P-r=20.2 mu C/cm(2) and V-c = 1.35 V and P-r= 15 mu C/cm(2) and V-c = 1.69 V for the films obtained from basic and acid solutions, respectively. (C) 2005 Elsevier B.V. All rights reserved.

Oriented growth of Bi3.25La0.75Ti3O12 thin films on RuO2/SiO2/Si substrates by using the polymeric precursor method: Structural, microstructural and electrical properties

c-axis oriented Bi3.25La0.75Ti3O12 (BLT) thin films were grown on a RuO2 top electrode deposited on a (100) SiO2/Si substrate by the polymeric precursor method. X-ray diffraction and atomic force microscope investigations indicate that the films exhibit a dense, well crystallized microstructure having random orientations with a rather smooth surface morphology. The electrical properties of preferred oriented Bi3.25La0.75Ti3O12 (BLT) thin films deposited on RuO2 bottom electrode leaded to a large remnant polarization (P-r ) of 17.2 mu C/cm(2) and (V-c ) of 1.8 V, fatigue free characteristics up to 10(10) switching cycles and a current density of 2.2 mu A/cm(2) at 5 V. We found that the polarization loss is insignificant with nine write/read voltages at a waiting time of 10,000 s. Independently of the applied electric field the retained switchable polarization approached a nearly steady-state value after a retention time of 10 s.

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.

Ferroelectric and dielectric properties of lanthanum-modified bismuth titanate thin films obtained by the polymeric precursor method

Lanthanum-modified bismuth titanate, Bi4-xLaxTi3O12 (BLT), thin films with a La concentration of 0.75 was grown on Pt/Ti/SiO2/Si substrates by using the polymeric precursor solution and spin-coating method. The scanning electron microscopy (SEM) showed rounded grains, which is not typical for these system. The BLT films showed well-saturated polarization-electric field curve which 2P(r) = 41.4 muC/cm(2) and V-c = 0.99 V. The capacitance dependence on the voltage is strongly nonlinear, confirming the ferroelectric properties of the film resulting from the domains switching. These properties make BLT a promising material for FERAM applications.

Electrical characterization of lanthanum-modified bismuth titanate thin films obtained by the polymeric precursor method

Lanthanum-modified bismuth titanate, Bi4-xLaxTi3O12 (BLT), thin films with a La concentration ranging from 0 to 0.75 were grown on Pt/Ti/SiO2/Si substrates using a polymeric precursor solution and spin-coating method. The scanning electron microscopy shows a change of morphology with increasing the lanthanum concentration. The BLT films show well-saturated polarization-electric field curves whit remnant polarizations of 14.7, 20.5, 21.5, and 20.4 muC/cm(2) for x = 0, 0.25, 0.50 and 0.75, respectively. The dielectric constant of BLT (x = 0.75 mol% La) is equal to 158 while dielectric loss remain low (tandelta = 0.0018).

The effect of microwave annealing on the electrical characteristics of lanthanum doped bismuth titanate films obtained by the polymeric precursor method

Lanthanum doped bismuth titanate thin films (Bi3.25La0.75Ti3O12-BLT) were produced by the polymeric precursor method and crystallized in a domestic microwave oven and in conventional furnace. Using platinum coated silicon substrates configuration, ferroelectric properties of the films were determined with remanent polarization P-r and a coercive field E-c of 3.9 mu C/cm(2) and 70 kV/cm for the film annealed in the microwave oven and 20 mu C/cm(2) and 52 kV/cm for the film annealed in conventional furnace, respectively. The films annealed in conventional furnace exhibited excellent retention-free characteristics at low infant periods indicating that BLT thin films can be a promise material for use in nonvolatile memories. on the other hand, the pinning of domains wall causes a strong decay at low infant periods for the films annealed in the microwave furnace which makes undesireable the application for future FeRAMS memories. (c) 2005 Elsevier B.V. All rights reserved.

Synthesis by the polymeric precursor method and characterization of undoped and Sn, Cr and V-doped ZrTiO4

In this work, zirconium titanate doped with 0. 1, 0.2, and 0.4 mole% of tin, chromium and vanadium was synthesized by the polymeric precursors method and characterized by thermal analysis (TG/DTA), X-ray diffraction (XRD), nitrogen adsorption and scanning electronic microscopy (SEM). The powder presented two mass losses attributed to the exit of water and to the pyrolysis of the organic material. The surface area reduction observed from 500 degrees C indicates the beginning of the sintering process. All the dopants led to changes in the lattice parameters and to the decrease of both crystallite size and particle size. (c) 2005 Elsevier B.V. All rights reserved.

Effect of thermal treatment temperature on the crystallinity and morphology of LiTaO3 thin films prepared from polymeric precursor method

Lithium tantalate thin films (LiTaO3) with (50:50) stoichiometry were prepared by spin coating method using a polymeric organic solution. The films were deposited on silicon (100) substrates with 4 layers. The substrates were previously cleaned and then the solution of lithium tantalate was deposited by adjusting the speed at 5000 rpm. The thin films deposited were thermally treated from 350 to 600degreesC for 3 hours in order to study the influence of the thermal treatment temperature on the crystallinity, microstructure, grain size and roughness of the final film. X-ray diffraction (XRD) results showed that the films are polycrystalline and secondary phases free. The thickness of films was observed by scanning electron microscopy (SEM). The atomic force microscopy (AFM) studies showed that the grain size and roughness are strongly influenced by thermal treatment.

Fatigue-free behavior of Bi3.25La0.75Ti3O12 thin films grown on several bottom eletrodes by the polymeric precursor method

Fatigue-free Bi3.25La0.75Ti3O12 (BLT) thin films were grown on LaNiO3,RuO2, and La0.5Sr0.5CoO3 bottom electrodes in a microwave furnace at 700 degreesC for 10 min. The remanent polarization (P-r) and the drive voltage (V-c) were in the range of 11-23 muC/cm(2) and 0.86-1.56 V, respectively, and are better than the values found in the literature. The BLT capacitors did not show any significant fatigue up to 10(10) read/write switching cycles. (C) 2004 American Institute of Physics.

Microwave synthesis of calcium bismuth niobate thin films obtained by the polymeric precursor method

The crystal structure, surface morphology and electrical properties of layered perovskite calcium bismuth niobate thin films (CaBi2Nb2O9-CBN) deposited on platinum coated silicon substrates by the polymeric precursor method have been investigated. The films were crystallized in a domestic microwave and in a conventional furnace. X-ray diffraction and atomic force microscopy analysis confirms that the crystallinity and morphology of the films are affected by the different annealing routes. Ferroelectric properties of the films were determined with remanent polarization P-r and a drive voltage V-c of 4.2 mu C/cm(2) and 1.7 V for the film annealed in the conventional furnace and 1.0 mu C/cm(2) and 4.0 V for the film annealed in microwave furnace, respectively. A slight decay after 10(8) polarization cycles was observed for the films annealed in the microwave furnace indicating a reduction of the domain wall mobility after interaction of the microwave energy with the bottom electrode. (C) 2006 Elsevier Ltd. All rights reserved.