Ammonothermal Synthesis of Earth‐Abundant Nitride Semiconductors ZnSiN₂ and ZnGeN₂ and Dissolution Monitoring by In Situ X‐ray Imaging

Abstract

In this contribution, first synthesis of semiconducting ZnSiN 2 and ZnGeN 2 from solution is reported with supercritical ammonia as solvent and KNH 2 as ammonobasic mineralizer.T he reactions were conducted in custom-built highpressure autoclaves made of nickel-based superalloy.T he nitrides were characterized by powder X-ray diffractiona nd their crystal structures were refinedb yt he Rietveld method. ZnSiN 2 (a = 5.24637(4), b = 6.28025(5), c = 5.02228(4) , Z = 4, R wp = 0.0556) and isotypic ZnGeN 2 (a = 5.46677(10), b = 6.44640(12), c = 5.19080(10) , Z = 4, R wp = 0.0494) crystallize in the orthorhombic space group Pna2 1 (no. 33). The morphology and elemental composition of the nitrides were examined by electron microscopy and energy-dispersive X-ray spectroscopy (EDX). Well-definedsingle crystalswith adiameter up to 7 mmw ere grownb ya mmonothermal synthesis at temperatures between 870 and 1070 Ka nd pressures up to 230 MPa. Optical properties have been analyzed with diffuse reflectance measurements. The band gaps of ZnSiN 2 and ZnGeN 2 were determined to be 3.7 and 3.2 eV at room temperature, respectively.I ns itu X-ray measurements were performed to exemplarily investigate the crystallization mechanism of ZnGeN 2 .D issolution in ammonobasic supercritical ammonia between 570 and6 70 Kw as observed which is quite promising for the crystal growth of ternary nitrides under ammonothermalconditions.

Ammonothermal Synthesis and Optical Properties of Ternary Nitride Semiconductors Mg‐IV‐N2, Mn‐IV‐N2 and Li‐IV2‐N3 (IV=Si, Ge)

“…The alkali metal amides were obtainedi ns itu startingf rom the azides because of the available purity and chemical stabilityo ft he latter.I na nalogyt o the synthesis of Zn-IV-nitrides, [21] KNH 2 was preferred for syntheses of MgSiN 2 and MnSiN 2 ,w hilep hase-pure samples of MgGeN 2 and MnGeN 2 were only obtained with NaNH 2 as the mineralizer.M g/Mn were used in 20 %e xcess and Li in 50 % excess to facilitate complete conversion of the intermediates to the nitrides( see Experimental Section). Ammonobasic mineralizers MNH 2 (M=Li, Na, K) were added to increase solubility of the starting materials.…”

“…[15,[17][18][19] In this contribution, we presenta na mmonothermal approach forb ulk synthesis of thesec ompounds using highly pressurized ammonia as the reactionm edium. [21] In the present study,w e report on synthesis and opticalc haracterization of the ternary nitride semiconductors MgSiN 2 ,M gGeN 2 ,M nSiN 2 ,M nGeN 2 , LiSi 2 N 3 and LiGe 2 N 3 .T he products werea nalyzedb yp owderXray diffraction, bandgaps were evaluated using diffuse reflectance spectroscopy and electronic structure wasd etermined by DFT calculations based on the Korringa-Kohn-Rostoker (KKR) Green's function method. [21] In the present study,w e report on synthesis and opticalc haracterization of the ternary nitride semiconductors MgSiN 2 ,M gGeN 2 ,M nSiN 2 ,M nGeN 2 , LiSi 2 N 3 and LiGe 2 N 3 .T he products werea nalyzedb yp owderXray diffraction, bandgaps were evaluated using diffuse reflectance spectroscopy and electronic structure wasd etermined by DFT calculations based on the Korringa-Kohn-Rostoker (KKR) Green's function method.…”

Nitridophosphates: A Success Story of Nitride Synthesis

“…[33] Thesynthesis routes carried out at medium pressure encompass the condensation of molecular precursors and ammonothermal syntheses. We chose this lower limit to separate pressure ampoules,w hich are used for syntheses in which additional gas is released during the reaction, from regular solid-solid reactions in ampoules.The upper limit of 1GPa was chosen as it is above the safely attainable pressure of modern autoclave systems (p max = 3 10 8 Pa) but below the usually used pressures of large-volume presses.…”

“…[48] Moreover,i na utoclaves large quantities can be prepared at once,w hich is relevant for industrial upscaling.I n1 997, Jacobs and co-workers prepared HPN 2 / DPN 2 by ammonolysis of P 3 N 5 at 550 8 8Ca nd 600 MPa, and K 3 P 6 N 11 from P 3 N 5 and KNH 2 at 500 8 8Ca nd 600 MPa. [33,50] With these autoclaves,Z n 2 PN 3 and Mg 2 PN 3 have recently been prepared from P 3 N 5 and metal amides,the latter in the form of single crystals of up to 30 mmi nlength (Figure 8). 600 8 8C, 0.3 GPa) and Haynes 282 (max.…”

Nitridophosphate – eine Erfolgsgeschichte der Nitridsynthese

“…[33] Die verwendeten Syntheserouten im mittleren Druckbereich sind die Kondensationsreaktionen molekularer Vorläuferverbindungen und Ammonothermalsynthesen. Das untere Limit wählten wir, um Druckampullen, also Reaktionen, bei denen zusätzlich Gas freigesetzt wird, von regulären Fest-Fest-Reaktionen abzugrenzen.…”