Up and down conversion photoluminescence and structural properties from hafnium doped with different lanthanides and lithium

Abstract The structural and photoluminescent results of the lanthanum, erbium, ytterbium and lithium doped hafnium oxide phosphors; are presented. These powders were synthesized by the solvent evaporation technique, different percentages of doping of the lanthanides were carried out, obtaining monoclinic and cubic phases, also a cubic phase is present when doping lanthanides with 28% mol. Up-conversion (UC) and down-conversion (DC) luminescence spectra when excited with a 980 nm laser, three emission regions are presented; two in the visible (up-conversion) and one in the infrared (downshift), are observed. The green emission located at 528 nm, 543 nm and 559 nm; associated whit transitions of erbium ion (2H11/2 + 4S3/2) → 4I15/2 and in the red emission located at 653 nm and 678 nm; associated whit transitions of erbium ion (4F9/2 + 4I9/2) → 4I15/2. In 1532 nm, the infrared down conversion associated electronic transition 4I13/2 → 4I15/2 of erbium ion. The luminescence emission intensity increase in green is 336 times and in red is 105 times when doping with lithium in comparison with samples without lithium co-doped. In the XRD diffractograms shown the monoclinic, cubic and mix of the phases in the phosphors; these are confirmed with the TEM diffraction patterns. The EDS result indicates the presence of HfO2, Er3+ and Yb3+, in the phosphorus; hafnium decreases due to the presence of ions lanthanides. XPS showed changes in energy values due to doping of lanthanides. The CIE diagram indicates that HfO2 doped phosphors have a variety of shades from red to yellow.