Abstract
This work investigates pressure-induced excited-state-crossover phenomena in Cr3+-doped LiCaAlF6 at room temperature. The aim is to find the structural requirements yielding the change in the Cr3+ photoluminescence (PL) behaviour from a single broadband emission, which is located at 1.62 eV (765 nm) at ambient conditions, to a ruby-like narrow-line emission at 1.87 eV (662 nm). For this purpose, emission and excitation spectroscopy as well as lifetime measurements as a function of pressure were performed in the 0–35 GPa range. Interestingly, we have been able to transform the broadband Cr3+ PL at ambient pressure into a ruby-like emission at 28 GPa. This behaviour, together with the variations of the 2E and 4T2 excited-state energies, and the PL lifetime with pressure, can be explained on the basis of the electron–ion coupling associated with the 4T2 and 2E states.
Acknowledgements
Financial support from the MEC (Project Ref. MAT2005-00099) is acknowledged. F.R. and I.H. thank the support from the University of Cantabria through the Research Intensification program I3. M.N.S. thanks the MEC for a FPU grant (Ref. AP-2004-5954).