The phosphorus nitrides, Mg PN and Zn PN , are wide band gap semiconductor materials with potential for application in (opto)electronics or photovoltaics. For the first time, both compounds were synthesized ammonothermally in custom-built high-temperature, high-pressure autoclaves starting from P N and the corresponding metals (Mg or Zn). Alkali amides (NaNH , KNH ) were employed as ammonobasic mineralizers to increase solubility of the starting materials in supercritical ammonia through formation of reactive intermediates. Single crystals of Mg PN , with length up to 30 μm, were synthesized at 1070 K and 140 MPa. Zn PN already decomposes at these conditions and was obtained as submicron-sized crystallites at 800 K and 200 MPa. Both compounds crystallize in a wurtzite-type superstructure in orthorhombic space group Cmc2 , which was confirmed by powder X-ray diffraction. In addition, single-crystal X-ray diffraction measurements of Mg PN were carried out for the first time. To our knowledge, this is the first single-crystal X-ray study of ternary nitrides synthesized by the ammonothermal method. The band gaps of both nitrides were estimated to be 5.0 eV for Mg PN and 3.7 eV for Zn PN by diffuse reflectance spectroscopy. DFT calculations were carried out to verify the experimental values. Furthermore, a dissolution experiment was conducted to obtain insights into the crystallization behavior of Mg PN .

The first gallium-containing nitridosilicate CaGaSiN was synthesized in newly developed high-pressure autoclaves using supercritical ammonia as solvent and nitriding agent. The reaction was conducted in an ammonobasic environment starting from intermetallic CaGaSi with NaN as a mineralizer. At 770 K, intermediate compounds were obtained, which were subsequently converted to the crystalline nitride at temperatures up to 1070 K (70-150 MPa). The impact of other mineralizers (e.g., LiN , KN , and CsN ) on the product formation was investigated as well. The crystal structure of CaGaSiN was analyzed by powder X-ray diffraction and refined by the Rietveld method. The structural results were further corroborated by transmission electron microscopy, Si MAS-NMR, and first-principle DFT calculations. CaGaSiN crystallizes in the orthorhombic space group Cmc2 (no. 36) with lattice parameters a=9.8855(11), b=5.6595(1), c=5.0810(1) Å, (Z=4, R =0.0326), and is isostructural with CaAlSiN (CASN). Eu doped samples exhibit red luminescence with an emission maximum of 620 nm and FWHM of 90 nm. Thus, CaGaSiN :Eu also represents an interesting candidate as a red-emitting material in phosphor-converted light-emitting diodes (pc-LEDs). In addition to the already known substitution of alkaline-earth metals in (Ca,Sr)AlSiN :Eu , inclusion of Ga is a further and promising perspective for luminescence tuning of widely used red-emitting CASN type materials.

Nitridophosphates are aw ell-studied class of compounds with high structural diversity.H owever,t heir synthesis is quite challenging, particularly due to the limited thermal stability of starting materials like P 3 N 5 .T ypically,i tr equires even high-pressuret echniques (e.g. multianvil) in most cases.H erein, we establish the ammonothermal method as av ersatile synthetic tool to access nitridophosphates with different degrees of condensation. a-Li 10 P 4 N 10 , b-Li 10 P 4 N 10 ,L i 18 P 6 N 16 ,C a 2 PN 3 ,S rP 8 N 14 ,a nd LiPN 2 were synthe-sized in supercritical NH 3 at temperatures and pressures up to 1070 Ka nd 200 MPa employing ammonobasic conditions. The products were analyzed by powder X-ray diffraction, energy dispersive X-ray spectroscopy,a nd FTIR spectroscopy. Moreover,w ee stablished red phosphorus as as tartingm aterial for nitridophosphate synthesis instead of commonly used and not readily availablep recursors, such as P 3 N 5 .T his opens ap romisingp reparativea ccess to the emerging compound class of nitridophosphates.

Nitridophosphates exhibit an intriguing structural diversity with different structuralm otifs, for example, chains, layers or frameworks. In this contribution the novel nitridophosphate Sr 3 P 3 N 7 with unprecedented dreier double chains is presented. Crystalline powders were synthesized using the ammonothermal method, while single crystals wereo btained by ah igh-pressurem ultianvil technique. The crystal structure of Sr 3 P 3 N 7 was solved and refinedf rom single-crystal X-ray diffraction and confirmed by powderX -ray meth-ods. Sr 3 P 3 N 7 crystallizes in monoclinic space group P2/c. Energy-dispersive X-ray and Fourier-transformed infrared spectroscopy were conducted to confirm the chemical composition, as well as the absence of NH x functionality. Theo ptical band gap was estimated to be 4.4 eV using diffuse re-flectanceU V/Vis spectroscopy.U pon doping with Eu 2 + , Sr 3 P 3 N 7 showsabroad deep-red to infrared emission (l em = 681 nm, fwhm % 3402 cm À1 )w ith an internal quantum efficiencyo f42%.

Grimm–Sommerfeld analogous II‐IV‐N2 nitrides such as ZnSiN2, ZnGeN2, and MgGeN2 are promising semiconductor materials for substitution of commonly used (Al,Ga,In)N. Herein, the ammonothermal synthesis of solid solutions of II‐IV‐N2 compounds (II=Mg, Mn, Zn; IV=Si, Ge) having the general formula (IIa 1−xIIb x)‐IV‐N2 with x≈0.5 and ab initio DFT calculations of their electronic and optical properties are presented. The ammonothermal reactions were conducted in custom‐built, high‐temperature, high‐pressure autoclaves by using the corresponding elements as starting materials. NaNH2 and KNH2 act as ammonobasic mineralizers that increase the solubility of the reactants in supercritical ammonia. Temperatures between 870 and 1070 K and pressures up to 200 MPa were chosen as reaction conditions. All solid solutions crystallize in wurtzite‐type superstructures with space group Pna21 (no. 33), confirmed by powder XRD. The chemical compositions were analyzed by energy‐dispersive X‐ray spectroscopy. Diffuse reflectance spectroscopy was used for estimation of optical bandgaps of all compounds, which ranged from 2.6 to 3.5 eV (Ge compounds) and from 3.6 to 4.4 eV (Si compounds), and thus demonstrated bandgap tunability between the respective boundary phases. Experimental findings were corroborated by DFT calculations of the electronic structure of pseudorelaxed mixed‐occupancy structures by using the KKR+CPA approach.