Evolution of microstructure in BaTiO 3 thin films recrystallised by laser

Abstract

Barium titanate ceramic thin films fabricated by the electrophoretic deposition technique were recrystallised using scanned CO₂ laser irradiation. Conventionally the film is sintered at high temperature (1200°C) to increase adhesive forces between powdered ceramic film and substrate. During this process, however, many micropores and microcracks are produced owing to large shrinkage of fine aggregate grains in the film layer. In order to produce preferred orientation grainswithout these defects, the films were instantaneously melted by laser irradiation and recrystallised. The microstructure of the resulting thin film showed significant growth of platelike crystals and strip grain morphology on the surface. The recrystallised phase of BaTiO₃ was tetragonal. Thus the laser scanning process appears to be suited to generating large grains with preferred orientation. In hysteresis D–E curve measurements, remanent polarisation of 48 mCm ^–2 and coercive field of 320 kVm^–1 were the best dielectric and ferroelectric properties obtained in a film of 4 μm thickness.