Synthesis of system CaSnO<sub>3</sub> : Yb<sup>3+</sup>,Er<sup>3+</sup>,Но<sup>3+ </sup>system and IR-excitation study of its luminescence
Features of solid-phase synthesis and a research technique of the perovskit structure of calcium stannat activated by three ions of the rare-earth elements Yb<sup>3+</sup>, Er<sup>3+</sup>, Ho<sup>3+</sup> are described. It is established that for the formation of luminescent structure of CaSnO<sub>3</sub> : Yb<sup>3+</sup>, Er<sup>3+</sup>, to Ho<sup>3+</sup> the following conditions of synthesis are required: calcination temperature 1250 °C and duration at least 18 h. the luminescent properties of the samples for excitation were probed by a semiconductor laser diode with a 960 nm wavelength. Luminescence emission bands in the visible and IR-regions were recorded. We show that Yb<sup>3+</sup> ions preferentially act as sensitizers and are capable to transfer part of the absorbed energy to Er<sup>3+</sup> ions and Ho<sup>3+</sup>, causing a luminescence gain in the bands corresponding to them. Er<sup>3+</sup> ions also transfer part of the absorbed energy to Ho<sup>3+</sup> ions, and therefore an intensity gain of IR luminescence in the bands at 1194 and 1950 nm is observed. The diagram of energetic transitions is provided for the CaSnO<sub>3</sub> : Yb<sup>3+</sup>, Er<sup>3+</sup>, Ho<sup>3+</sup> system for excitation by a laser with a 960 nm wavelength, and the mechanism of energy transmission between ions of Yb<sup>3+</sup>, Er<sup>3+</sup>, Ho<sup>3+</sup> is explicitly described. The dependence of the luminescence intensity of the studied phosphor in the area 994, 1194, 1550, 1950 nm on the concentration of Ho<sup>3+</sup> ions is studied. The intensity maxima for the emission bands at 1194 and 1950 nm are observed for Ho<sup>3+</sup> ion concentration of 0.007 atomic shares. It is suggested to use the CaSnO<sub>3</sub> : Yb<sup>3+</sup>, Er<sup>3+</sup>, Ho<sup>3+</sup> luminescent structure as the source of radiation capable to transform IR radiation in the 960 nm region to IR radiation with a wavelength of about 2000 nm.