Nanocomposites and nanomaterials

Luminescent properties of amorphous glass-like compounds based on alkaline earth metal oxides
S. V. Vasylyuk1,2,3, S. V. Simchenko2
1. Faculty of Physics, Taras Shevchenko National University of Kyiv, 64/13, Volodymyrska Street, 01601, Kyiv, Ukraine
2. State University of Telecommunications, 7, Solomenska street, 03110, Kyiv, Ukraine
3. International European University, 42/ V, Academician Glushkov Avenue,  03187, Kyiv, Ukraine 
•	*Corresponding author: svitlanafvasylyuk@gmail.com

In recent years, there has been scientific and practical interest in studying the luminescent properties of oxides based on alkaline earth metals. This interest is driven by their potential for creating high-performance phosphors and solid-state lasers with lamp pumping [1]. Calcium oxide (CaO), barium oxide (BaO), and potassium oxide (K2O) are widely used in optical devices and light-emitting devices operating in the visible spectrum and exhibiting luminescent properties. To obtain samples of (CaO)x(P2O5)y, (BaO)x(P2O5)y, and (K2O)x(P2O5)y, the method of vacuum melting of high-purity substances was used. Manganese was added step by step during the melting process to achieve better homogeneity of the melt with parallel stirring. Optimal melting conditions and melt stirring were chosen based on existing experimental data.The samples were polished plates measuring 50x15x15 mm. Manganese was added for doping in various percentage ratios. In this work, the influence of manganese concentration (Mn) on the luminescence intensity of these glass-like compounds was investigated.
For excitation of luminescence, a nitrogen laser LGN-10 with a wavelength of 337 nm was used. Luminescent characteristic studies were carried out at room temperature (20°C) under constant voltage and with the signal amplification coefficient from the photomultiplier tube (PMT). Luminescence spectra were examined using the spectral complex KSVU-12 in automatic mode. The photocurrent signal from the PMT was amplified by an original design instrumental amplifier [2] and recorded using a high-speed analog-to-digital converter (ADC). The measurement results were simultaneously displayed in real-time on a computer screen and recorded in a data file on a hard disk. Figure 1 shows the photoluminescence spectra of the investigated samples activated with manganese (a-b-c) with manganese content ranging from 1% to 10%. The dependence of luminescence intensity on the amount of activating impurity is also shown (g).

Figure 1. Photoluminescence spectra of oxide compounds based on: (a) (BaO)x(P2O5)y, (b) (K2O)x(P2O5)y, (c) (CaO)x(P2O5)y, doped with manganese (1-10%) and the dependence of emission intensity on the concentration of the doping impurity (g). 1 - (BaO)x(P2O5)y, 2 - (K2O)x(P2O5)y, 3 - (CaO)x(P2O5)y.
From the graphs, it can be observed that the introduction of manganese doping leads to the emergence of a single emission band (with a wavelength of approximately 672 nm), indicating the activating property of manganese. The spectral peaks are relatively narrow, indicating the elemental nature of the emitting centers. This suggests that the observed emission band is caused by centers of the same type. It can be hypothesized that the main luminescence band is due to the formation of paired and triple associates of Mn2+ ions in the investigated compounds.A comparative analysis of the position of the spectral peaks and the emission intensity showed that the percentage ratio of manganese practically does not affect the emission wavelength, while the luminescence intensity varies proportionally to the percentage content of manganese in the sample.