Growth of Yb : Na2SO4 crystals and study of their spectral - luminescent characteristics

Ytterbium-doped single crystals of the high-temperature hexagonal sodium sulphate modification are grown by the Czochralski method. It is found by energy dispersive analysis that the crystallisation occurs congruently. The Yb : Na2SO4 crystals have additional (with respect to Yb3+ ions) absorption bands in the regions of 650, 850 and 1150 nm, which obviously belong to colour centres. The luminescence spectrum of the Yb : Na2SO4 single crystal noticeably differs from the luminescence spectrum of Yb : YAG crystals by the presence of a broad band without a prominent peak. The luminescence decay curve for the powder is single-exponential with a time constant of 1175 μs, which is somewhat larger than that for the Yb : YAG crystal. The lifetime of the ytterbium excited state does not change during storage of the samples in air for a week.