Sol-gel synthesis of tetragonal BaTiO₃ thin films under fast heating

BaTiO₃ thin films with a thickness of 400 nm were prepared by spin coating onto a quartz plate and subsequently calcined at 700 °C. The effect of fast (540 K min⁻¹) and slow (10 K min⁻¹) heating on morphology, unit cell parameter and dielectric constant was studied. Fast heating yields tetragonal BaTiO₃ films with a semiconductor band gap of 3.54 eV, dielectric constant of 685 and a surface roughness of 12 nm. In contrast, slow heating produces tetragonal BaTiO₃ films with a larger band gap of 3.78 eV, a dielectric constant of 219 and a surface roughness of 35 nm. A kinetic constant of 0.0061 min⁻¹ was obtained in the decomposition of methylene blue with UV light over BTO films at 20 °C.