Luminescence, electronic absorption and vibrational IR and Raman studies of binary and ternary cerium ortho-, pyro- and meta-phosphates doped with Pr3+ ions

The broad class of polycrystalline ortho-[Ba3Ce(PO4)3, Ca3Ce(PO4)3, Ba6Ce(PO4)5, K3Ce(PO4)2. Na3Ce(PO4)2, Na3−xKxCe(PO4)2 (x = 0.5, 1.5 and 2.5)], pyro-[NaCeP2O7] and meta-[NaCe(PO3)4, KCe(PO3)4, K2Ce(PO3)5] phosphates was prepared in the solid state reaction. The Pr3+ ions have been used as active probe for studies of the spectroscopic properties of these materials. Optical absorption, emission as well as infrared and Raman spectroscopic methods have been applied to characterise the properties and structure of the compounds studied. Their electronic spectra were discussed in terms of the Ce3+ ion spectroscopic characteristics. The 2F5/2 → 2F7/2 transition appears in the typical for this ion region, i.e., at about 2000 cm−1. The absorption bands in the range 25,000–50,000 cm−1 have been assigned to the 4f1 → 5d1 transitions of the cerium ion. The role of these transitions in the radiative and radiation-less energy transfer mechanism was discussed. This paper discusses also the emission of Ce3+ and Pr3+ and Stokes shift.