Preparation of micro-spherical ZrO2: Pr3+ phosphors by ultrasonic assisted CVS

Polycrystalline micro-spheres of undoped (ZO) and praseodymium-doped zirconia (PrZO) were obtained for different reactor temperatures (Tr) by the ultrasonic assisted chemical vapor synthesis process. SEM micrographs for Tr C 400 C show that (a) the materials were synthesized in a powder form in the presence of particles spherical in shape with an average size of 3 lm and a narrow size distribution, and (b) the production of spherical particles had a remarkable increase on rate production and no considerable changes on their average size as Tr rises. EDS studies show an atomic percent composition of O-67.5, Zr-30.0, Pr-0.3, and Cl-2.2 for PrZO micro-spheres obtained at 500 C, which is in good agreement with zirconium oxide stoichiometry. XRD patterns of ZO and PrZO micro-spheres for Tr C 400 C show a polycrystalline tetragonal I structure with crystallite size values remaining below 20 nm. The photoluminescence emission spectrum of PrZO micro-spheres shows peaks overlapping the intrinsic emission of zirconia, attributed to inter-level transitions in Pr3+ ions: 490 and 505 nm: 3P0 - 3H4, 565 nm: 3P1 + 1I6 - 3H5, 615 nm: 1D2 - 3H4 and 645 nm: 3P0 - 3H6. The excitation spectrum for the main emission peak (615 nm) shows that Pr3+ ions in PrZO show a preferred excitation through its 4f5d absorption band.