Influence of solvents on the microstructure and dielectric properties of Ba0.5Sr0.5TiO3 thin films prepared by a diol-based sol-gel process


BaxSr1-xTiO3 (BST, x = 0.5) thin films were prepared on Pt/TiO2/SiO2/Si substrates using a diol-based sol-gel method. Two different solvents were employed, ethylene glycol and propylene glycol (1,2-propanediol). The influence of the solvent on the sol structure, microstructure development, and dielectric properties of BST thin films is analyzed and discussed. It is observed that films prepared with ethylene glycol show higher values of the dielectric permittivity (similar to 40% higher) and lower values of dielectric losses when compared with films prepared from propylene glycol precursors. The dielectric permittivitty is 459 and 302 at 1 kHz for films prepared with ethylene glycol and 1,2-propanediol, respectively, and annealed at 800 degrees C. IR Studies revealed that the stabilization of a titanium precursor with propylene glycol is incomplete. During the phase-formation process, a higher content of a second phase is formed for the propylene glycol-delivered films. However, microstructure analyses revealed smaller grain size and surface roughness and higher density for films prepared with ethylene glycol. These differences are attributed to the relative high boiling point and latent heat of vaporization and to the linear molecular structure of ethylene glycol. Ethylene glycol as a solvent allows for the preparation of BST thin films with improved dielectric properties.




Chemistry; Materials Science


Gonzalez, MB; Wu, AY; Vilarinho, PM

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