Fluorescence of Pr3+-ions in La1−xPrxP5O14

The fluorescence spectrum of La_1?xPr_xP₅O₁₄ was investigated for the range of 0.001 ? x ? 1. For small Pr³⁺-concentration the fluorescence starts almost completely from the ¹D₂ level, whereas in pure PrUP the total fluorescence arises from the energetically higher ³P₀ level. This is contrary to the usually observed concentration quenching. In the intermediate concentration range fluorescence lines from both levels are observed independent of the excitation.