Synthesis, Crystal Structure and Photoluminescent Properties of Red-Emitting CaAl4O7:Cr3+ Nanocrystalline Phosphor

Calcium dialuminate, CaAl4O7, nanopowders with a grossite-type structure, doped with chromium ions, were synthesized via the combined sol-gel solution combustion method. The evolution of phase composition, crystal structure, and microstructural parameters of the nanocrystalline materials depending on the temperature of the thermal treatment was investigated via X-ray powder diffraction and applying the Rietveld refinement technique. The photoluminescent properties of CaAl4O7 nanophosphors activated with Cr3+ ions were studied over the temperature range of 4.5-325 K. The samples show deep red and near-infrared luminescence due to the E-2 ? (4)A(2) and T-4(2) ? (4)A(2) energy level transitions of Cr3+ ions under excitation in the two broad emission bands in the visible spectral region. The R lines emission reveals a strong temperature dependence. The feasibility of the material for non-contact luminescence sensing is investigated, and good sensitivity is obtained based on the (R2/R1) luminescence intensity ratio and the lifetime of the emission.

Automated summary

Calcium dialuminate, CaAl4O7, nanopowders doped with chromium ions were synthesized via sol-gel solution combustion method. The effects of thermal treatment temperature on the phase composition, crystal structure, and microstructure of the nanocrystalline materials were investigated. The photoluminescent properties of the CaAl4O7 nanophosphors activated with Cr3+ ions were studied, showing deep red and near-infrared luminescence.