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Praseodymium-doped ZrO 2 photoluminescent (PL) powders have been prepared by a co-precipitation process. Different doping concentrations in the start mixture and annealing temperatures for the precipitated were studied. It is observed that the crystalline structure and the crystallinity of the powders depend on the annealing temperature. For temperatures higher than 750˚C, the material presents the monoclinic phase with an average crystalline grain size of 100 nm. Measurements on photoluminescence show excitation and emission spectra. For an excitation wavelength of 294 nm, all the PL emission spectra show the peaks located at 490

ZrO2 : Pr films were synthesized by the ultrasonic spray pyrolysis process. X-ray diffraction studies, as a function of the deposition temperature, indicate a tetragonal crystal structure of zirconia as the substrate temperature was increased. Luminescence (photo- and cathodoluminescence) properties of the films were studied as a function of growth parameters such as the substrate temperature and the praseodymium concentration. For an excitation wavelength of 290 nm, all the photoluminescent emission spectra show peaks located at 490, 510, 566, 615, 642, 695, 718, 740 and 833 nm, associated with the electronic transitions 3 P0 → 3H4, 3P0 → 3 H4, 3P1 + 1I6 → 3H5, 1D2 → 3H4, 3 P0 → 3H6, 1D2 → 3 H5, 1D2 → 3H5, 3 P0 → 3F3,4 and 1D2 → 3 F2 of the Pr3+ ion. As the deposition temperature is increased, an increasing intensity of the luminescence emission is observed. Also, quenching of the luminescence, with increasing doping concentration, is observed. The chemical composition of the films as determined by energy dispersive spectroscopy is reported as well. In addition, the surface morphology characteristics of the films, as a function of the deposition temperature, are presented.

Cathodoluminescent (CL) powders of zinc aluminate activated with samarium ions have been prepared by a co‐precipitation chemical process. Different doping concentrations in the start mixture and sintering temperatures for the precipitated powder were studied. It was observed that the crystalline characteristics of the powders depend upon the sintering temperature. For temperatures higher than 450 °C, the powders presented the cubic spinel phase with a lattice parameter value of 8.0756 Å, and grain sizes from 50 to 100 nm with semispherical shape. The CL emission spectra showed broad bands localized at 564, 602, 644, and 703 nm associated with 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, 4G5/2 → 6H9/2, and 4G5/2 → 6H11/2 transitions in the Sm3+ ions, respectively. Concentration quenching of the cathodoluminescence occurred at about 4.26 at% of the activator (Sm) concentration inside the sintered powders. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Praseodymium doped zirconia powder (ZrO 2 : (0.53 at%) Pr 3+ ) was prepared by a co-precipitation technique and annealed in air at a temperature T a = 950 • C. The x-ray diffraction pattern shows a nanocrystalline structure composed of 29.6% monoclinic and 70.4% cubic-tetragonal phases. Medium infrared and Raman analysis confirms the monoclinic/cubic-tetragonal crystalline structure and proves the absence of praseodymium aggregates in the material. Photoluminescent spectroscopy over excitations of 457.9 and 514.9 nm (at 20 K), shows two emission spectra composed of many narrow peaks in the visible-near infrared region (VIS-NIR) of the electromagnetic spectrum, associated with 4f inter-level electronic transitions in praseodymium ions incorporated in the zirconia. Excitation and emission spectra show the different mechanisms of the direct and non-direct excitation of the dopant ion (Pr 3+ ), and the preferential relaxation of the material by charge transfer from the host (zirconia) to the 4f5d band and the 4f inter-level of the dopant ion (Pr 3+ ). No evidence of energy transfer from the host to the dopant was observed.