Luminescent P2O5-MoO3-Bi2O3-K2O Glasses and Glass-Ceramics on Their Basis: Insights from Experimental and Computational Studies

This paper presents the results of complementary experimental (electron microscopy, X-ray diffraction, diffuse reflectance, photoluminescence (PL), and FTIR spectroscopy) and computational (molecular dynamics and DFT-based electronic structural) studies of oxide glasses of xP2O5-yMoO3-zBi2O3-(1-x-y-z)K2O systems and glass-ceramics based on these (crystal @glass), where the KBi(MoO4)2 complex oxide is the crystal component (KBi(MoO4)2 @glass). The behavior of the observed PL characteristics is analyzed in synergy with the results of the calculations of their atomic structures and changes in the oxygen environment of bismuth atoms during the transition crystal → interphase → glass. It is shown that the optical absorption and PL characteristics of such systems are largely determined by the content of Bi2O3 and MoO3 oxides in the initial charge and by the content of bismuth ions in different charge states that exist in the produced glass and glass-ceramics. It was found that the blue PL (spectral range 375–550 nm) of both the glasses and the glass-ceramics originated from radiative transitions 3P1 → 1S0 in Bi3+ bismuth ions. The yellow-red PL (range 550–850 nm) was mainly associated with the luminescence of bismuth ions in lower charge states, Bi2+, Bi+, and Bi0. The thickness of the interphase layers of glass-ceramics was estimated to be 1.5–2.0 nm. It was found that the changes in the spectra of optical absorption and the PL/PL excitation of the glass-ceramics occurred due to the decrease in the number of oxygen atoms in the nearest surrounding bismuth ions in the interphase region. These changes can be used for the spectral probing of the formation and presence of interphase layers.