Preparation of binary single-phase line compounds via diffusion couples: The subnitride phases [eta]-Hf[sub 3]N[sub 2[minus]]x and [zeta]-Hf[sub 4]N[sub 3[minus]]x

Journal Article · Tue Nov 30 23:00:00 EST 1993 · Acta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-7151(93)90230-P· OSTI ID:5960955

Lengauer, W; Rafaja, D; Taeubler, R; Kral, C; Ettmayer, P ^[1]

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1. Vienna Univ. of Technology, Getreidemarkt (Austria). Inst. for Chemical Technology of Inorganic Materials

It is shown that diffusion couples allow the preparation of pure line compounds, i.e. compounds with a very narrow homogeneity region, which are otherwise difficult or even impossible to prepare in single-phase form. With appropriate reaction conditions even a line compound forms a relatively large core in a symmetric diffusion couple of finite plane-sheet diffusion geometry due to the formation of a flat diffusion profile in the centered phase. The core of such a diffusion couple can then be isolated to obtain single-phase (and compact) material. This was shown for the phases [eta]-Hf[sub 3]N[sub 2[minus]x] and [zeta]-Hf[sub 4]N[sub 3[minus]x], which have a homogeneity region of only 2.5 at.% and <1 at.%N, respectively, in the temperature range of 1,200-1,700 C. The diffusion process was characterized by computational simulation, metallography, EPMA and XRD. By means of powder XRD and chemical nitrogen analysis it was possible to obtain more precise data on the two subnitride phases. [eta]-Hf[sub 3]N[sub 2[minus]x] has hexagonal lattice parameters of a=0.32124(1) and c=2.32790(10)nm for [N]/([Hf] + [Zr]) = 0.58(1) and 2.5 wt%Zr, and [zeta]-Hf[sub 4]N[sub 3[minus]x] has hexagonal lattice parameters of a=0.32084(1) and c=3.10800(9)nm for [N]/([Hf] + [Zr]) = 0.62(1) and 3.1 wt%Zr. By this technique of a single-phase sample of a [zeta]-phase, [zeta]-Hf[sub 4]N[sub 3[minus]x], could be prepared for the first time.

• OSTI ID: 5960955
• Journal Information: Acta Metallurgica et Materialia; (United States), Journal Name: Acta Metallurgica et Materialia; (United States) Vol. 41:12; ISSN 0956-7151; ISSN AMATEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
&amp; Refractories-- Preparation &amp; Fabrication
360202 -- Ceramics
Cermets
&amp; Refractories-- Structure &amp; Phase Studies
ALLOYS
DIFFUSION
FABRICATION
HAFNIUM COMPOUNDS
HAFNIUM NITRIDES
LATTICE PARAMETERS
MICROSTRUCTURE
NITRIDES
NITROGEN COMPOUNDS
PHASE STUDIES
PNICTIDES
REFRACTORY METAL COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM ADDITIONS
ZIRCONIUM ALLOYS