Synthesis and Upconversion Luminescence in LaF₃:Yb³⁺, Ho³⁺, GdF₃: Yb³⁺, Tm³⁺ and YF₃:Yb³⁺, Er³⁺ obtained from Sulfide Precursors

Abstract

Rare earth fluorides are mainly obtained from aqueous solutions of oxygen-containing precursors. Probably, this method is simple and efficient, however, oxygen may partially be retained in the fluoride structure. We offer an alternative method: obtaining fluorides and solid solutions based on them from an oxygen-free precursor. As starting materials, we choose sulfides of rare-earth elements and solid solutions based on them. The fluorination is carried out by exposure to hydrofluoric acid of various concentrations. The transmission electron microscopy images revealed the different morphologies of the products, * I. A. Razumkova Fax: +73452597559 E-Mail: razumkova@list.ru [a]

Europium (II) Sulfate EuSO4: Synthesis Methods, Crystal and Electronic Structure, Luminescence Properties

“…The rate of interaction of sulfides with sulfuric acid is mainly influenced by two factors: -formation in the course of the reaction of a hindering layer of insoluble compound on the surface of the particles -structural difficulty associated with much greater symmetry and density of ball packing in the structure of europium monosulfide, compared, for example, with sesqui-sulfides of rare earth elements, which easily interact with aqueous solutions of acids. [47,48] To reduce these factors, it was decided to carry out the reaction of sulfide powder with a 10 % solution of H 2 SO 4 when exposed to ultrasonic vibrations. Here, a weighted portion of europium monosulfide weighing 0.50 g was placed in a beaker and a small amount of water was added so that it moistened all the monosulfide.…”

The nature of the interaction of RE(NO3)3 (yttrium subgroup) with HF or NH4F

“…The starting oxides RE 2 O 3 (DyÀ Lu, Y) were calcined in air in corundum crucible in a muffle furnace at 900 °C to decompose the hydroxides and carbonates formed during storage. [41][42][43] Nitrate of rare earth elements solution (1 M) were prepared by dissolving appropriate oxides in concentrated HNO 3 . Drop wise RE(NO 3 ) 3 was added to the solution of HF (or NH 4 F) in the stoichiometric amount 1 : 5.…”

Enhancement of Red Upconversion Emission of ZnS: Er3+/Yb3+ Powders Synthesized via Solid Phase Reaction Method by Introducing Metal Fluoride

“…While, many researches have synthesized luminescence materials with strong upconversion emission but with a low doping concentration. [5][6] Encouragingly, it is proved that the upconversion emission intensity of Er 3 + /Yb 3 + codoped luminescent materials is remarkably enhanced by introducing metal ions (Li + , Na + , K + , Zn 2 + , Mg 2 + , Ca 2 + ). [7][8][9][10][11] Such as, both the morphology and luminescence properties of Li (1-x-y) Na x K y YF 4 :Yb 3 + /Er 3 + are greatly affected by the doping ratio of Li, Na and K ions in the matrix, and when the mol ratio of the Li:Na : K was 10 : 6 : 9, the luminous intensity was 20 times higher than that of NaYF 4 :Yb 3 + /Er 3 + prepared under the same condition.…”

“…Regularly, the emission intensity of is too low to apply. While, many researches have synthesized luminescence materials with strong upconversion emission but with a low doping concentration [5–6] …”