B.D. Stojanović

Secondary phases in Nb-doped BaTiO3 ceramics

Univ Mar del Plata, CONICET, INTEMA, Inst Invest Ciencia & Tecnol Mat, RA-7600 Mar Del Plata, Argentina

Influence of oxygen atmosphere on crystallization and properties of LiNbO3 thin films

Thin films of lithium niobate were deposited on the Pt/Ti/SiO2 (111) substrates by spin coating from the polymeric precursor method (Pechini process). Annealing in static air and oxygen atmosphere was performed at 500 � C for 3 h. The films obtained were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The dielectric constant and dissipation factor were measured in frequency region from 10 Hz to 10 MHz. Electrical characterization of the films pointed to ferroelectricity via hysteresis loop. The influence of oxygen atmosphere on crystallization, morphology and properties of LiNbO3 thin films is discussed. # 2003 Elsevier Ltd. All rights reserved.

LiNbO3 thin films prepared through polymeric precursor method

Thin films of lithium niobate were deposited on (100) silicon by the polymeric precursor method (Pechini method). Annealing in static air was performed at 500 °C for 3 h. The films obtained were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Electrical characterization of the films pointed to ferroelectricity via hysteresis loop. The dielectric constant, dissipation factor and resistance were measured in the frequency region from 10 Hz to 10 MHz. At 1 MHz, the dielectric constant was 46 and the dissipation factor was 0.043.

Ferroelectric properties of mechanically synthesized nanosized barium titanate

Barium titanate ceramics were prepared through mechanochemical synthesis starting from fresh prepared barium oxide and titanium oxide in rutile form. Mixture of oxides was milled in zirconia oxide jar in the planetary ball-mill during 30, 60, 120 and 240 min. Extended time of milling directed to formation of higher amount of barium titanate perovskite phase. Barium titanate with good crystallinity was formed after 240 min. Sintering without pre-calcinations step was performed at 1330°C for 2 hours with heating rate of 10°C/min. The XRD, DSC, IR and TEM analyses were performed. Electric and ferroelectric properties were studied. Very well defined hysteresis loop was obtained.

Synthesis and deposition of ZnO based particles by aerosol spray pyrolysis

Abstract Spray pyrolysis was used for the deposition of well defined submicronic to nanosize particles based on ZnO. The influence of the temperature in the range from 345 to 1165 K, solution concentration (0.004 and 1.5 mol dm−3) and the residence time on the particle morphology is discussed. X-ray diffraction, differential scanning calorimetry and scanning electron microscopy were used in particle characterization. With the presumption that certain particle morphology is formed during the evaporation/drying stage of spray pyrolysis, the corresponding mathematical model for droplets evaporation is developed and correlated with the empirical results.

Effect of Magnesium on the Properties of LiNbO 3 Thin Films Prepared from Polymeric Precursors

The effect of magnesium addition on the phase formation, microstructure and electric and ferroelectric properties of LiNbO 3 thin films prepared through polymeric precursors was analyzed. By X ray diffraction no secondary phase was observed with the increase of magnesium concentration. Comparing to pure LiNbO 3 , the addition of 0.5 and 1.0 mol% of Mg +2 increased of the dielectric constant, while 2.0 mol% decreased it. It was noticed that the increase in additive concentration decreases the ferroelectric remanent polarization and increases the coercive field.

Influence of thickness on crystallization and properties of LiNbO3 thin films

Thin films of lithium niobate were deposited on Pt/Ti/SiO{sub 2} (111) substrates by spin coating from the polymeric precursor method (Pechini process). Annealing in static air was performed at 500 deg. C for 3 h. The obtained films were characterized by X-ray diffraction and atomic force microscopy. The dielectric constant, dissipation factor and resistance were measured in frequency region from 10 Hz to 10 MHz and the hysteresis loop was obtained. The influence of number of layers on crystallization, morphology and properties of LiNbO{sub 3} thin films is discussed.

Effects of annealing on the crystallization and roughness of PLZT thin films

Abstract Lead lanthanum zirconate titanate (PLZT) thin films with stoichiometry (9/65/35) were prepared by a dip-coating process using a polymeric organic solution. The solution viscosity was adjusted in the range of 15–56 cP. Silicon (100) substrates were previously cleaned and then immersed in the solution. The withdrawal speed of substrate from the solution was adjusted within a range of 5–20 mm/min. The coated substrates were thermally treated in the 450–700°C temperature range. Surface roughness and crystallization of these films are strongly dependent on the annealing conditions. Infrared and X-ray diffraction data for PLZT powders heat-treated at 650°C for 3 h show that the material is free of carbonate phases and crystalline.

Effect of precursor solution on the formation of perovskite phase of Pb(Mg1/3Nb2/3)O3 thin films

Precursor solutions for Pb(Mg Nb )O (PMN) synthesis were obtained by Pechini’s method. The influence of the 1y 32 y 33 concentration of organic materials on the phase formation has been studied. For this purpose, PMN solutions were prepared with different precursors and were characterized by thermogravimetric and differential thermal analysis. The obtained solutions were deposited onto a Si (100) substrate by dip coating and pre-treated in a hot plate at 300 8C for 1 h. The films were annealed at 600, 700, 800 and 900 8C for 1 h and characterized by X-ray diffraction. The perovskite phase was formed after annealing at 600 and 700 8C when the solution of PMN was prepared with a lower amount of organic material and starting with niobium oxide. By increasing the temperature to 800 or 900 8C, only the formation of pyrochlore phase was observed. With the solution prepared from niobium ethoxide, only the presence of pyrochlore phase was observed independently of the annealing temperature. 2002 Elsevier Science B.V. All rights reserved.

Hot-pressed 9.5/65/35 PLZT prepared by the polymeric precursor method

Abstract A 9.5/65/35 PLZT ceramic with a Pb 0.905 La 0.095 (Zr 0.65 Ti 0.35 ) 0.976 O 3 +3.5 w% PbO formula was prepared using the Pechini method for powder preparation and two-step sintering in an oxygen atmosphere. The first step consisted of sintering at 1200°C for 4 h with slow heating and cooling rates. The second step consisted of hot pressing at 1200°C for 4 h, with slow heating and cooling rates and pressing pressures of 20 MPa (initial pressure) and 40 MPa (at sintering temperature). Investigations were made of the powder phase formation and powder morphology, i.e. the structure of sintered and hot-pressed PLZT ceramics. SEM microstructural analyses were carried out on the sintering and hot-pressing processes.