Influence of the Calcination Temperature on the Structure and Optical Properties of Bi3.25La0.75CoTi2O12 Powders

Abstract

The wide band gap of complex oxides is one of the major obstacles limiting their use in optoelectronic devices. To control the band gap of wide complex oxides, cobalt-doped lanthanum-modified bismuth titanates powders (Co-BLT) were synthesized using a solid-state reaction at various calcination temperatures. The structural and optical properties were analyzed by X-ray diffraction (XRD) and ultraviolet-visible (UV-vis) absorption spectroscopy. XRD confirmed that the samples calcined at 700 degrees C crystallized in an orthorhombic structure without breaking symmetry, while the samples calcined under 600 degrees C formed the alpha-Bi2O3 phase and the samples calcined at high temperatures (800, 900 degrees C) formed a Bi-based secondary phase. UV-vis absorption spectroscopy showed that the optical band gap decreased gradually from 2.82 eV to 1.56 eV with increasing calcination temperature from 300 to 900 degrees C. The optimal calcination temperature to reduce the optical band gap was 700 degrees C. Tuning of the band gap using different calcination temperatures might be applicable to other complex oxides materials for use in emerging oxide optoelectronic devices.