The effects of temperature and impurity phases on the luminescent properties of Ce3+-doped Ca3Sc2Si3O12 garnet

The luminescent properties of Ce3+ ions in Ca3Sc2Si3O12 were studied in the temperature range of 77-800 K. It was found, for the first time, that at 77 K zero-phonon lines of 5d↔4f transitions and vibronic structure are distinctly observed in the Ce3+ emission and excitation spectra. The decay time of the Ce3+ emission in Ca3Sc2Si3O12 was found to be nearly constant (~ 71 ns) up to 700 K. This indicates that the thermal quenching of the Ce3+ emission in Ca3Sc2Si3O12 starts at high temperatures (≥ 750 K). The decrease of the Ce3+ integrated emission intensity (upon direct excitation of the lowest-energy Ce3+ 5d1 state) with increasing temperature in the range of 350-700 K, often attributed to the thermal quenching, probably arises from temperature changes of 4f→5d1 transition absorption strength. It was shown that typical impurity phases (β-Ca2SiO4, CaSiO3, CeO2) can cause competing "parasitic" absorption in the 250-380 nm range and they are expected to be responsible for variations in the luminescence excitation and diffuse-reflection spectra reported in the literature for Ce3+-doped Ca3Sc2Si3O12. A comparison with literature data on Ce3+-doped aluminum garnets (Y3Al5O12 and Lu3Al5O12) is also made.