Improved photoluminescence and electrical properties of Eu- and Gd-codoped bismuth titanate ferroelectric thin films

Abstract

Eu- and Gd-codoped bismuth titanate [Bi3.15Eu0.425Gd0.425Ti3O12], thin films as well as Bi3.15Eu0.85Ti3O12 (BEuT) and Bi3.15Gd0.85Ti3O12 (BGdT) thin films were prepared on indium-tin-oxide-coated glass substrates by chemical solution deposition and the photoluminescence, ferroelectric, and dielectric properties of the thin films were investigated. All the thin films exhibited a polycrystalline bismuth-layered perovskite structure. Photoluminescence studies showed that the enhancement of emission intensities for two Eu3+ emission transitions of D05→F17 (594nm) and D05→F27 (617nm) was observed for the BEGT thin films as compared to BEuT thin films. This photoluminescence improvement can be attributed to Eu content of BEGT thin films close to quenching concentration of BEuT thin films and local distortion of crystal field surrounding the Eu3+ activator induced by different ionic radii of Eu3+ and Gd3+ ions. Electrical measurements indicated that BEGT thin films had larger remanent polarization and higher dielectric constant than BGdT and BEuT thin films prepared under the same experimental conditions. These results suggest that codoping of rare earth ions such as Eu and Gd in bismuth titanate thin films is an effective way to improve photoluminescence and electrical properties of the thin films.