Missing Member in the M II M IIISi4N7 Compound Class: Carbothermal Reduction and Nitridation Synthesis Reveal Substitution of Nitrogen by Carbon and Oxygen in CaLu[Si4N7–2x C x O x ]:Eu2+/Ce3+ (x≈0.3)

• Published in: Chemistry : a European journal Vol. 28; no. 4
• Main Authors: Gamperl, Lisa, Zeman, Otto E. O., Strobel, Philipp, Schmidt, Peter J., Schnick, Wolfgang
• Format: Journal Article
• Language: English
• Published: Hoboken John Wiley and Sons Inc 08-12-2021
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202104007

The nitridosilicate CaLu[Si
4
N
7–2
x
C
x
O
x
] (
x
≈0.3) was synthesized by carbothermal reduction and nitridation starting from CaH
2
, Lu
2
O
3
, graphite and amorphous Si
3
N
4
at 1550 °C in a radiofrequency furnace. CaLu[Si
4
N
7–2
x
C
x
O
x
] (
x
≈0.3) crystallizes isotypically to many previously known
M
II
M
III
Si
4
N
7
compounds in the space group
P
6
3
mc
, 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
13
C and
29
Si MAS NMR spectroscopy. For the first time in the
M
II
M
III
Si
4
N
7
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[Si
4
N
7–2
x
C
x
O
x
] (
x
≈0.3). When excited with UV‐to‐blue light, CaLu[Si
4
N
7–2
x
C
x
O
x
] (
x
≈0.3) shows an emission maximum in the blue spectral region (
λ
em
=484 nm; fwhm=4531 cm
−1
) upon doping with Ce
3+
, whereas Eu
2+
‐doped CaLu[Si
4
N
7–2
x
C
x
O
x
] (
x
≈0.3) exhibits a yellow‐green emission (
λ
em
=546 nm; fwhm=3999 cm
−1
).
Carbon copy
: The oxonitridocarbidosilicate CaLu[Si
4
N
7–2
x
C
x
O
x
] (
x
≈0.3) has been synthesized by carbothermal reduction and nitridation. Incorporation of carbon was confirmed by
13
C and
29
Si MAS NMR spectroscopy. Complementary EDX measurements suggest that simultaneous incorporation of oxygen compensates for the negative charge excess induced by carbon. Eu
2+
‐ and Ce
3‐
doped CaLu[Si
4
N
7–2
x
C
x
O
x
] (
x
≈0.3) exhibit yellow‐green and blue emission, respectively.