Effects of chemically induced cationic disturbance on Mn4+ luminescence in double perovskites - temperature and pressure experimental and computational studies

We show the opportunity for tuning of the spectral position of the Mn4+ red emission in the series of double perovskites, Ba2LaNbO6:Mn4+, Ba2La(Nb0.8,Zr0.1,W0.1)O6:Mn4+, and Ba2La(Zr0.5,W0.5)O6:Mn4+ with increasing chemically induced symmetry disturbance. Such a disorder appeared attractive to engineering phosphors for pressure sensors or horticultural applications, for instance. The goal of the present research, not yet systematically addressed in the literature, was to unveil the correlation between chemically induced controlled crystal lattice distortion and the luminescence of Mn4+. For this purpose, the luminescence of these phosphors was methodically investigated at different pressures and temperatures. A pressure-induced redshift of photoluminescent lines with the rate of − 4 cm−1/kbar was found within the 0–230 kbar range, and the emission peak moved from 685 to 740 nm then. Furthermore, the cationic disorder allowed tuning of the Mn4+ luminescence making it useful for horticultural applications with a better fit between the emission wavelength and the strong chlorophyll absorption in the deep red part of the spectrum. The Mn4+ energy levels were computationally determined using the exchange charge model of the crystal-field theory which allowed for a deeper understanding of the experimental results. We found a correlation between the introduced disorder of the cationic subsystem and the energy of the Mn4+ emitting 2Eg level (R-line) as well as its intensity. This research brought a deeper understanding of the Mn4+-activated phosphors and, in turn, provides tips for a prudent search of materials for advanced practical uses.