1. Novel multifunctional nitrides for fusion applications Andreas Zerr UPR Laboratoire des Sciences des Procédés et des Matériaux CNRS, Université Paris Nord, Villetaneuse, France

2. Traditional binary nitrides
At P= 1bar: product of the reaction M + x.N2 → MN
M3N4
M3N2 MN
M3N

3. Novel high-pressure binary nitrides with N:M>1
At P > 5 GPa: product of the reaction M + x.N2 →
P3N5
W3N4
W2N3
M(N2)
Novel dense phases of Si3N4, Ge3N4
Novel compound Sn3N4
M3N4, Ta2N3

4. Novel high-pressure binary nitrides with N:M>1
At P > 5 GPa: Our contribution
Novel dense phases of Si3N4, Ge3N4
Novel compound Sn3N4
M3N4, Ta2N3

5. High-pressure synthesis

6. Synthesis of c-Zr3N4 / c-Hf3N4 having cubic Th3P4 structure
LH-DAC
ZrN + N2  c-Zr3N4
Hf + N2  c-Hf3N4
~18 GPa; ~2800 K
Size: up to 100 mm
50 mm
Zerr, Miehe, Riedel, Nature Mater. 2, 185 (2003)
Multianvil
nc-Zr3N4+x  c-Zr3N4
nc-Hf3N4+x  c-Hf3N4
~ 7-12 GPa; ~1600 K
Size: up to 5 mm
Dzivenko et al., Adv. Mater. 19, 1869 (2007)

7. Novel high pressure nitrides with N:M>1
As for any high-pressure products we expected :
Higher density: ρproduct > ρstarting (Le Chatelier’s principal)
Higher elastic moduli
Higher hardness
Possible Bonus(es):
Novel compounds (e.g. M3N4 instead of MN) – novel properties
- Elevated thermal or chemical stability
- Toughness, wear resistance
Optoelectronic applications (electronic structure, band gap)
Resistant to neutron irradiation (?)

8. Radiation tolerant spinel nitride, g-M3N4
“structural vacancies” in spinel structure:
- 7/8 of tetrahedral sites are free “self-healing”
- 1/2 of octahedral sites are free
Spinel-nitrides: Energetic costs of cation antisites formation = 0

9. Radiation tolerant spinel oxide, g-AB2O4 (e.g. MgAl2O4)
“structural vacancies” in spinel structure:
- 7/8 of tetrahedral sites are free “self-healing”
- 1/2 of octahedral sites are free A O B
Spinel-oxides: Energetic costs of cation antisites formation > 0

10. Spinel nitrides of the group 14 elements: g-M3N4 (M = Si, Ge, Sn)

11. Band gaps of g-M3N4 and exciton binding energies
Experiment (SXS):
band gap
Theory (modified Becke-Johnson potential, MBJLDA):
direct transition
Direct or nearly direct band gaps
Large Eexc – high conversion efficiency LEDs
Lighting applications (true visible light?)
g-Sn3N4 ↔ GaAs (LEDs, PV, mobile phones, HF)
Experimentally confirmed for g-Si3N4
Museur, Zerr, Kanaev; Sci. Rep. (2016)
Boyko et al., Phys. Rev. Lett. (2014)

12. Deposition of g-Sn3N4 spinel XRD Maruyama & Morishita (1995):
RF magnetron sputtering 50 W, Sn + N2 substrate - glass, Tsubstrate=60 oC
hexagonal structure
CONFIRMED BY
Caskey et al., J. Mater. Chem. C (2015)
spinel
111
220
311
222
400
422
511
440
531
622
620
533
642
731
XRD

13. END