Temperature and pressure dependence of the optical properties of Cr ~(3 +)-doped Gd_3Ga_5O_(12) nanoparticles

摘要

Since the crystal-field strength at the Cr~(3 +) site is very close to the excited-state crossover (ESCO), this work investigates the optical properties of Cr~(3 +)-doped Gd_3Ga_5O_(12) (GGG) nanoparticles as a function of temperature and pressure in order to establish the effect of the ESCO on the optical behaviour of nanocrystalline GGG. Luminescence, time-resolved emission and lifetime measurements have been performed on GGG:0.5%Cr~(3 +) nanoparticles in the 25-300K temperature range, as well as under hydrostatic pressure up to 20GPa. We show how low temperature and high pressure progressively transforms broadband emission into a ruby-like luminescence. This behaviour together with the lifetime dependence on pressure and temperature are explained on the basis of the spin-orbit interaction between the ~4T_2 and ~2E states of Cr~(3 +).