Ammonothermal Synthesis of Novel Nitrides: Case Study on CaGaSiN₃

Abstract

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.

Ammonothermal Synthesis of the Mixed‐Valence Nitrogen‐Rich Europium Tantalum Ruddlesden‐Popper Phase EuIIEuIII2Ta2N4O3

“…Eu II Eu III 2 Ta 2 N 4 O 3 was synthesized by an ammonothermal approach using custom‐built high‐temperature autoclaves made of nickel‐based superalloy , . Metallic Ta and Eu were used as powders.…”

“…Subsequently, the autoclave was heated to the respective reaction temperature within 6 h and kept at this temperature for 110 h. The pressure slowly decreased over time because of hydrogen loss of the autoclave. Further details of the used autoclaves can be found in literature , , , …”

“…Recently, the ammonothermal approach has again been utilized for explorative synthetic solid‐state chemistry of novel complex nitrides, e.g. CaGaSiN 3 , ZnSiN 2 , ZnGeN 2 , Zn 2 PN 3 as well as nitride oxide perovskites such as Ln TaN 2 O with Ln = La, Ce, Pr, Nd, Sm and Gd and EAM NO 2 with EA = Sr, Ba and M = Nb, Ta , . Novel materials with mixed anions such as nitride oxides came into research focus in the last decade.…”

Crystalline Nitridophosphates by Ammonothermal Synthesis

“…[1][2][3][4][5] The ammonothermal technique gainedf undamentali nterest in materials science as it facilitates the growth of high-quality GaN single crystalsu pt o 50 mm in diameter with growth rates of several hundred mm per day. [10][11][12][13][14][15] Applyingt he ammonothermal technique, even the challenging preparation of afew nitridophosphates has been accomplished successfully as reportedf or K 3 P 6 N 11 andt he double nitrides Mg 2 PN 3 and Zn 2 PN 3 . [10][11][12][13][14][15] Applyingt he ammonothermal technique, even the challenging preparation of afew nitridophosphates has been accomplished successfully as reportedf or K 3 P 6 N 11 andt he double nitrides Mg 2 PN 3 and Zn 2 PN 3 .…”

Ammonothermal Synthesis of Ba2PO3N – An Oxonitridophosphate with Non‐Condensed PO3N Tetrahedra

“…InN, II‐IV‐N 2 (II = Mg, Mn, Zn; IV = Si, Ge), CaGaSiN 3 or Ca 1– x Li x Al 1– x Ge 1+ x N 3 ( x ≈ 0.2)] and oxide nitride perovskites [e.g. EAM O 2 N ( EA = Sr, Ba; M = Nb, Ta)] as well . Most recently, the syntheses of numerous nitridophosphates with different degrees of condensations κ (i.e.…”