# Synthesis of γ-Sn3N4 from the elements in a laser-heated DAC and its thermal shock resistance estimated from the high-pressure Raman spectroscopic data

Andreas Zerr, Gerhard Miehe

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Andreas Zerr, Gerhard Miehe. Synthesis of γ-Sn3N4 from the elements in a laser-heated DAC and its thermal shock resistance estimated from the high-pressure Raman spectroscopic data. 61st European High Pressure Research Group (EHPRG) Meeting), Aristotle University of Thessaloniki, Sep 2024, Thessaloniki, Greece. pp.87. hal-05377316

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https://hal.science/hal-05377316v1

Submitted on 21 Nov 2025

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# Synthesis of γ-Sn₃N₄ from the elements in a laser-heated DAC and its thermal shock resistance estimated from the high-pressure Raman spectroscopic data

A. Zerr*¹, G. Miehe²

¹Laboratoire des Sciences des Procédés et des Matériaux, CNRS, Villetaneuse, France

²FB Material- und Geowissenschaften, Technische Universität Darmstadt, Darmstadt, Germany

Tin(IV) nitride having spinel structure, γ-Sn₃N₄, is a narrow-band-gap semiconductor with a direct band gap of E_g = 1.6(2) eV and strong exciton binding energy of ~69 meV¹, suitable for the fabrication IR-LEDs exhibiting a high energy-conversion efficiency. Also, γ-Sn₃N₄ appears to be one of very few materials combining a direct band gap of E_g < 2 eV with the alignment of its conduction and valence bands with the water redox potentials, needed for an efficient photo-electrochemical splitting of water². The above properties and the possibility to deposit γ-Sn₃N₄ as thin films via economic magnetron sputtering²⁻⁴ make γ-Sn₃N₄ an attractive candidate for the industrial production of green hydrogen.

Here, we synthesized γ-Sn₃N₄ from the elements, Sn and N₂, at pressures between 16-20 GPa and temperatures around 2000 °C using a laser heated diamond anvil cell. In order to avoid the contamination with carbon⁵⁻⁷, the samples were separated from the diamond anvils by the disks of dried NaCl of ~10 µm in thickness. Contamination with oxygen was excluded via the condensation of high-purity nitrogen in the sample volume using a gas. Presently, this is the most reliable way to obtain high-pressure nitrides with negligible oxygen- and carbon contaminations. Brownish color of our products confirmed that γ-Sn₃N₄ is a narrow-band-gap semiconductor. We collected Raman spectra of the products after the synthesis and upon pressure decrease. Also, we examined the recovered product using powder XRD and refined the spinel structure of γ-Sn₃N₄. From the measured pressure dependences of the observed Raman-band frequencies, we derived the average mode Grüneisen parameter of γ-Sn₃N₄ to be 〈γ〉=0.95. We showed that the knowledge of Grüneisen parameters allows a comparison of thermal shock resistances of rigid solids if their hardness or yield stress is known. In particular, this material property is proportional to the ratio of yield strength to Grüneisen parameter: σ_y/γ. Because σ_y is proportional to hardness, H, the ratio H/γ<sub>th</sub> can equally well be used for the comparison of thermal shock resistances of hard ceramic materials. Applying this approach, we have found that thermal shock resistance of γ-Sn₃N₄ is moderate when compared with that of γ-Si₃N₄, another member of the spinel-nitrides family, and β-Si₃N₄ known to be highly thermal-shock resistant. However, the thermal shock resistance of γ-Sn₃N₄ is better than that of GaAs presently used for the fabrication of high-flux-density IR-LEDs operating in pulsed modes in optical fiber communications.

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<footnote>*Corresponding author: zerr@univ-paris13.fr</footnote>

<footnote>Keywords: HP-HT synthesis; spinel nitride; structure refinement; thermal shock resistance</footnote>