ENGINEERING OF THE LUMINESCENT PROPERTIES OF GLASS-CERAMIC NANOCOMPOSITES

Abstract

The “mixture”- like composite materials consist of a matrix and a filler. An interaction between these components, i.e., the matrix and filler particles, can result in formation of the transition layers (interphases). A chemical composition, spatial and energetic structures of these interphase layers differ from those peculiar for initial components. Accordingly, the properties of such transitional layers could be significantly different from those ones for a matrix or a filler. The role of interphase layers increases when particles became nanosized and with their concentration increasing. An influence of the interphase layers on the properties of composite increases at such conditions and even could be determining. The considerations described above are a basement of the proposed method of control (engineering) of the composite materials properties. This paper reports the results of the study of the interphase layers manifestations in luminescence properties of the “glass-ceramics” type of composites, those consist of mK2O-kP2O5-nB2O3:xPb-yEu oxide glass matrix and Eu3+- doped luminescent oxide polycrystalline KCa(BO3)3compound, as a filler. A possibility of tailoring the emission wavelength of the glass-ceramics has been discussed as well. A morphology, structure and optical properties of the prepared glass-ceramics have been studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy, respectively. The SEM images are typical for vitreous materials when some micro/nanocrystallites of KCa(BO3)3 oxide incorporated into matrix can be seen in case of glass-ceramics. XRD patterns reveal wide bands those are peculiar to vitreous materials, while the patterns of glass-ceramics additionally contain the narrow bands related with crystalline filler. Wide-band spectra of own luminescence have been observed under photo-excitation of glassy samples. In contrast, weakening of this PL emission and a domination of a linear emission related with f-f transitions in Eu3+ ions, takes place in the case of glass-ceramics. A detailed analysis of the linear PL has been shown the presence of three types of Eu3+ ions in glass-ceramics: there are ions located in the oxide particles, glass and interphase layer. Spectral characteristics of the PL related with each of these types of ions are significantly different, that provide a possibility to control PL emission spectra by changing contribution of interphase layer to overall spectra of the glass ceramics studied.