Some Observations on the Cr3+ Fluorescence in the Huntite Structure

Absorption and emission spectra of Cr3+‐activated huntites of the type Ln3+Me3+3B4O12 (Ln = Y or Eu, Me = Al or Ga) are reported. For the aluminium and gallium compounds the crystal field splitting of the Cr3+ ion is about equal, but the electrostatic interaction parameter B is different. The Cr3+ emission of these compounds, unlike the emission of ruby, consists of lines and bands. In EuAl3B4O12:Cr, nonradiative energy transfer from Eu3+ to Cr3+ is observed; in YGa3B4O12: Cr nonradiative energy transfer occurs from the host lattice (probably GaO6 groups) to Cr3+.