High pressure studies of Eu²⁺ and Mn²⁺ doped NaScSi₂O₆ clinopyroxenes

High pressure luminescence studies of NaScSi₂O₆ clinopyroxene (jervisite) doped with Eu²⁺ and Mn²⁺ are reported. The efficiency of the energy transfer between Eu²⁺ and Mn²⁺ is examined. It is shown that the efficiency of the energy transfer process is weakly dependent on pressure, although a small increase of the probability of nonradiative energy transfer with increase of pressure is observed. In contrast to that the energy transfer efficiency at ambient pressure is independent of temperature between 10 K and 400 K. The Raman spectra under pressure shows fingerprints of the reversible phase transitions at pressures of about 100-120 kbar at room temperature. The occurrence of the phase transition drastically reduces the efficiency of energy transfer, which is restored at higher pressures. The Mn²⁺ luminescence is quenched at about 200 kbar due to the crossing between the ⁴T_1g and ²T_2g excited states occurring at this pressure. The ²T_2g state becomes the first excited level at this pressure and due to much stronger coupling with the host the Mn²⁺ luminescence is quenched. This is the first observation of such behaviour for Mn²⁺ ions. Pressure dependence of CIE color coordinates is established for this phosphor.