Synthesis and crystal structures of new phases in the system Hf–Ta–O–N

Titelangaben

Hund, Sophie ; Bubnov, Nikita ; Lüdtke, Tobias ; Duarte-Correa, Liseth ; Pöttker-Menke, Jonathan ; Selve, Sören ; Wurl, Stefan ; Lunkenbein, Thomas ; Mei, Bastian ; Lerch, Martin:
Synthesis and crystal structures of new phases in the system Hf–Ta–O–N.
In: Zeitschrift für Naturforschung B. Bd. 80 (2025) Heft 6-7 . - S. 285-294.
ISSN 1865-7117
DOI: https://doi.org/10.1515/znb-2025-0025

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Abstract

New phases in the system Hf–Ta–O–N have been synthesized and characterized by means of SEM/STEM-EDX, hot gas extraction analysis, and pXRD including Rietveld refinement. Bixbyite-type phases crystallizing in the cubic space group Ia¯3 have been prepared with three different cation ratios: Hf0.67Ta1.33N3.11 (a = 9.890(2) Å), HfTaN3 (a = 9.919(2) Å), and Hf1.33Ta0.67O0.33N2.67 (a = 9.960(3) Å). In contrast to the corresponding Zr/Ta-containing phases, the lattice parameters are almost independent from the overall nitrogen/oxygen contents. This may be explained by the presence of crystallites with narrow phase widths partly covered by oxidic surface layers of variable thickness (detectable by STEM-EDX). Furthermore, a baddeleyite-type phase HfTaO3N (monoclinic space group P21/c, a = 5.043(2) Å, b = 5.101(5) Å, c = 5.243(2) Å, β = 99.465(9)°) has been synthesized as pale-yellow powder. No significant activity for OER was detectable.