Electrophoretic deposition of Ba(Ti0.85Zr0.15)O3 nanoparticles to fabrication of laser sintered ferroelectrics thick films

Author(s)

Eduardo Antonelli

• Document type: Doctoral Thesis
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Instituto de Física de São Carlos (IFSC/BT)
• Defense date: 2008-11-28

Examining board members

Antonio Carlos Hernandes; Sandra Helena Messaddeq; Paulo Barbeitas Miranda; Celso Valentim Santilli

• Advisor: Antonio Carlos Hernandes

Abstract

The goals of this work were the implantation and optimization of the technique of sintering by laser scan of thick films, the kinetic study of the process and the evaluation of the physical properties of the laser sintered compound BaTi0.85Zr0.15O3 (BTZ), compared to thick films sintered in conventional furnace. Nanocrystalline powders of BTZ were for the first time, successfully synthesized at low temperatures (600ºC) using the modified polymeric method. Nanometric powders with primaries particles of ~20nm sizes and controlled agglomeration were obtained which was an innovation for BTZ powders prepared by chemical methods. For the films deposition, the suspensions stability was studied and thick films with excellent homogeneity were deposited using the electrophoresis technique (EDP). The developing of the technique allowed the thicknesses control using the deposition parameters. The characteristics of the experimental apparatus were optimized in such a way as to allow the sintering of thick films whose dimensions were up to 70mm in length, 10mm in width and variable thicknesses. The step times in each stage were dependent on the velocity and scan number. The maximum temperature that can be achieved in the thick film, during each scan, and for a fixed rated laser power was correlated with the relative density. The related thermal process during the continuous laser scan acted in a similar way as a two-step sintering. To improve the densification of the films, we started to add the compound Bi4Ti3O12 (BIT) (1 e 2 mol %) to BTZ during the deposition. The utilization of the system developed for the sintering by laser scan alongwith the adding of the BIT resulted in a grain size decrease and a significant decrease in apparent porosity. For the 2mol% additivation we obtained films with excellent density (apparent porosity of ~4%) and reduced grain size (~200nm), which is an unpublished result for thick films. The laser sintering resulted in films with a higher dielectric permittivity in relation to the conventionally sintered film. The reactions between BTZ and BIT were explored using the techniques of impedance spectroscopy, thermal analysis and X-ray diffraction. (AU)