Yttrium oxide (Y₂O₃) is interesting host material for high power laser applications. Y₂O₃ belongs to group oxides with very high melting point. For yttria this is 2430 ⁰C. At about 2280 ⁰C its structural phase transition is observed. Furthermore its thermal conductivity is higher then well-known yttrium aluminum garnet (YAG) crystals and their thermal expansion coefficient is very similar. Moreover sesquioxide Y₂O₃ can be doped by rare earth ions and it is a good phosphor used in optical displays and light emitting devices.

In this work the nanosized powders of the following systems: Y₂O₃; Y₂O₃:Nd³⁺; Y₂O₃:Yb³⁺; Y₂O₃:Nd³⁺, Yb³⁺ were prepared by sol-gel method using EDTA, 1,2-Ethanediol and citric acid. Finally the one phase compounds of Y₂O₃ doped 0,5 % Nd and 1, 2 or 4 % Yb were obtained.

The influence of thermal treatment on nanopowders properties were investigated. The gels were dried at 120 ^oC for 12 h and then grinded in an agate mortar to obtain fine powder. The xerogel powders were heat treated at various temperatures from 600 to 1200 ^oC in air. The calcining time was changed from 1 to 10 h.

The crystal structures of samples were characterized by X-ray diffraction (XRD) using a Siemens D-500 diffractometer with CuK_α radiation at λ = 1.548 Å. The size and morphology of nanopowders were analyzed by scanning electron microscopy (SEM) and were performed with DSM-950 microscope and high resolution scanning electron microscopy (HRSEM) was performed with LEO GEMINI 1530 microscope. Luminescence spectra were recorded with a Dongwoo Optron Fluorometer system.

Average size of crystallites was evaluated using Scherrer formula and the sizes were increased with the calcining temperature (600 ÷ 1200 ^oC) from 10 to 85 nm. Also morphology of crystallites was changed with the temperature of calcination. The calcining time was changed from 1 to 10 h and it did not influence on the crystallite sizes. There were not (evident) relationships between the crystallite sizes and the time of calcination (1 ÷ 10 h), the concentration of doping elements (Nd, Yb) and the used complexing chemical compounds.

Spectroscopic investigation of nanopowders revealed occurrence of intense emission in near infrared region. Three emission bands characteristic of Nd³⁺ and one emission band characteristic of Yb³⁺ were recorded for Y₂O₃:Nd³⁺ and Y₂O₃:Yb³⁺ samples respectively. For Y₂O₃:Nd³⁺, Yb³⁺ samples the emission consists essentially of one band related to partially overlapping transitions of Yb³⁺ and Nd³⁺. Analysis of luminescence decay curves indicates that metastable states of the two ions are linked by fast nonradiative energy transfer processes.

This work was supported by Ministry of Education and Science under the research project no.3T11B00430.

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