Bismuth germanate films prepared by Pechini method

Bismuth germanate films were prepared by dip coating and spin coating techniques and the dependence of the luminescent properties of the samples on the resin viscosity and deposition technique was investigated. The resin used for the preparation of the films was obtained via Pechini method, employing the precursors Bi2O3 and GeO2. Citric acid and ethylene glycol were used as chelating and cross-linking agents, respectively. Results from X-ray diffraction and Raman spectroscopy indicated that the films sintered at 700 °C for 10 h presented the single crystalline phase Bi4Ge3O12. SEM images of the films have shown that homogeneous flat films can be produced by the two techniques investigated. All the samples presented the typical Bi4Ge3O12 emission band centred at 505 nm. Films with 3.1 μm average thickness presented 80% of the luminescence intensity registered for the single crystal at the maximum wavelength.