The crystal structures of Hf{sub 3+}-{sub {delta}}Nb{sub 4+}-{sub {delta}}As{sub 3} and Hf{sub 7.2}Nb{sub 3.8}As{sub 4}: Members of a homologous series combining W-type, Mg-type and AlB{sub 2}-type building blocks

Journal Article · Mon Mar 15 04:00:00 EDT 2010 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.12.028· OSTI ID:21372520

Chumak, Igor; Warczok, Piotr ^[1]

---

1. Department of Inorganic Chemistry/Materials Chemistry, University of Vienna, Waehringerstr. 42, A-1090 Wien (Austria)

Two new partially ordered compounds were synthesized in the system Hf-Nb-As by arc melting and subsequent annealing at 1400 deg. C and they were structurally characterized by means of single crystal X-ray diffraction. The compound Hf{sub 3+}-{sub {delta}}Nb{sub 4+}-{sub {delta}}As{sub 3} is isostructural to Zr{sub 3}Pd{sub 4}P{sub 3} and Hf{sub 3}Pd{sub 4}P{sub 3} (Space group: Pnma, Pearson symbol oP40) and shows a considerable homogeneity range between the limiting compositions Hf{sub 2.4}Nb{sub 4.6}As{sub 3} and Hf{sub 4.1}Nb{sub 2.9}As{sub 3}. Mixed occupation of Hf and Nb were found at all seven independent metal sites, with varying Hf/Nb ratios, so the compound is stabilized by differential fractional site occupation (DFSO). The compound Hf{sub 7.2}Nb{sub 3.8}As{sub 4} is isostructural with Zr{sub 6.45}Nb{sub 4.55}P{sub 4} (Immm, oI30) and was found to be metastable at the temperature of annealing (1400 deg. C). Similar to the type structure, Hf{sub 7.2}Nb{sub 3.8}As{sub 4} is stabilized by (DFSO). Structural relations of the two compounds with Hf{sub 1.5+{delta}}Nb{sub 1.5-{delta}}As (Pnma, oP16) are discussed. All three compounds belong to a homologous series M{sub k+2l+m}X{sub 2m} combining W-type, Mg-type and AlB{sub 2}-type building blocks. - Graphical abstract: Hf{sub 3+}-{sub {delta}}Nb{sub 4+}-{sub {delta}}As{sub 3} (Pnma, new structure type) is stabilized by differential fractional site occupation. Its structural relations within a homologous series based on W-type, Mg-type and Al{sub 2}B-type building blocks are discussed.

• OSTI ID: 21372520
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 3 Vol. 183; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANNEALING
ARSENIC COMPOUNDS
ARSENIDES
COHERENT SCATTERING
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
DIFFRACTION
HAFNIUM COMPOUNDS
HEAT TREATMENTS
MELTING
MONOCRYSTALS
NIOBIUM COMPOUNDS
ORTHORHOMBIC LATTICES
PHASE TRANSFORMATIONS
PNICTIDES
REFRACTORY METAL COMPOUNDS
SCATTERING
SPACE GROUPS
SYMMETRY GROUPS
TETRAGONAL LATTICES
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION