Photoluminescent emission of Pr3+ ions in different zirconia crystalline forms

Polycrystalline praseodymium doped-zirconia powders were synthesized by crystallization of a saturated solution and annealed in air at Ta = 950 °C. Monoclinic, tetragonal and cubic crystalline phases of zirconia were obtained. EDS studies showed homogeneous chemical composition over all the powders particles and chemical elemental contents in good agreement with the incorporation of Pr3+ ion in Zr4+ sites. XRD patterns showed stabilization of tetragonal and cubic phases at 1.28 and 2.87 at.% of Pr3+ doping concentrations, respectively. Both unit cells expand when Pr3+ content increases. All samples showed a crystallite size lower than 27 nm. Diffuse reflectance studies exhibited the presence of the 4f5d absorption band of Pr3+, and absorption peaks in 440–610 nm region associated with 4f inter-level electronic transitions in Pr3+ ion. Low temperature (20 K) photo-luminescent spectroscopic measurements over excitation of 488 nm for praseodymium doped zirconia, showed multiple emission peaks in the 520–900 nm range of the electromagnetic spectrum, associated with typical 4f inter-level electronic transition in Pr3+. Incorporation of Pr3+ in more than one zirconia crystalline phase and the incorporation in cubic C2 sites, were observed. Zirconia powders presented significant differences in its emission spectra as a function of the type of crystalline phase compounds.