BaTi2O5 thin films were prepared on MgO (100) substrates by pulsed laser deposition. The effect of substrate temperature (T-sub) On the structural and optical properties of the films, such as crystal phase, preferred orientation, crystallinity, surface morphology, optical transmittance and bandgap energy, was investigated. The preferred orientation of the films changed form (710) to (02 0) depending on T-sub, and the b-axis oriented BaTi2O5 thin film could be obtained at T-sub = 973-1023 K The surface morphology of the films was different with changing Tub, which showed a dense surface with an elongated granular texture at Tsub = 973-1023 K The crystallinity and surface roughness increased at the elevated substrate temperatures. The as-deposited BaTi2O5 thin films were highly transparent with an optical transmittance of similar to 70%. The bandgap energy was found to decrease with increasing substrate temperature, from 3.76 eV for T-sub = 923 K to 3.56 eV for T-sub = 1023 K. (C) 2008 Elsevier B.V. All rights reserved.