Missing Member in the MIIMIIISi4N7 Compound Class: Carbothermal Reduction and Nitridation Synthesis Reveal Substitution of Nitrogen by Carbon and Oxygen in CaLu[Si4N7–2xCxOx]:Eu2+/Ce3+ (x≈0.3)

January 5, 2022

Title

Missing Member in the MIIMIIISi4N7 Compound Class: Carbothermal Reduction and Nitridation Synthesis Reveal Substitution of Nitrogen by Carbon and Oxygen in CaLu[Si4N7–2xCxOx]:Eu2+/Ce3+ (x≈0.3)

Author

Lisa Gamperl, Otto E. O. Zeman, Philipp Stobel, Peter J. Schmidt, Wolfgang Schnick

Year

2021

Journal

Chemistry A European Journal

Abstract

The nitridosilicate CaLu[Si4N7–2xCxOx] (x≈0.3) was synthesized by carbothermal reduction and nitridation starting from CaH2, Lu2O3, graphite and amorphous Si3N4 at 1550 °C in a radiofrequency furnace. CaLu[Si4N7–2xCxOx] (x≈0.3) crystallizes isotypically to many previously known MIIMIIISi4N7 compounds in the space group P63mc, as was confirmed by Rietveld refinement based on powder X-ray diffraction data. Incorporation of carbon into the crystal structure as a result of the carbothermal synthesis route was confirmed by 13C and 29Si MAS NMR spectroscopy. For the first time in the MIIMIIISi4N7 compound class, complementary EDX measurements suggest that simultaneous incorporation of oxygen compensates for the negative charge excess induced by carbon, resulting in an adjusted sum formula, CaLu[Si4N7–2xCxOx] (x≈0.3). When excited with UV-to-blue light, CaLu[Si4N7–2xCxOx] (x≈0.3) shows an emission maximum in the blue spectral region (λem=484 nm; fwhm=4531 cm−1) upon doping with Ce3+, whereas Eu2+-doped CaLu[Si4N7–2xCxOx] (x≈0.3) exhibits a yellow-green emission (λem=546 nm; fwhm=3999 cm−1).

Instrument

V-650

Keywords

nitridosilicate, carbothermal,