Luminescence of Bi3+ in the orthorhombic perovskites CaB4+O3 (B4+=Zr, sn): Crossover from localized to D-state emission

The optical properties of Bi3+ in the orthorhombic perovskites CaZrO3 and CaSnO3 are investigated. The Stokes shift of Bi3+ emission in CaZrO3 is small (∼0.80 eV) with the peak wavelength of the emission band occurring in the ultraviolet. This emission is attributed to the localized 3P0,1 → 1S0 optical transition. In contrast, the Stokes shift of the Bi3+ emission in CaSnO3 is large (>1 eV) with the emission band peaking in the visible. The emission band is also considerably broadened in CaSnO3. It is claimed that Bi3+ luminescence in CaSnO3 corresponds with the Bi3+ (6s2) -Sn4+ (5s°) charge transfer emission (D-state emission). The energy of the 1S0→3P1 (A-band) excitation band in both perovskites are very nearly the same. Physical reasoning is advanced for the occurrence and lack thereof of the D-state emission in these perovskites.