Find in Library

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 ²E → ⁴A₂ and ⁴T₂ → ⁴A₂ 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.