THERMODYNAMIC ANALYSIS OF A NEW GAS-PHASE METHOD
OF OBTAINING HIGH-PURITY ALUMINUM NITRIDE
R. A. Shishkin,
A. A. Elagin,
A. R. Beketov,
and M. V. Baranov
Translated from Novye Ogneupory, No. 2, February, 2015.
Original article submitted December 2, 2014.
Ultradispersed high-purity aluminum nitride powder was obtained at the Physico-Technological Institute on a
unique experimental-industrial unit by a gas-phase method. The powder was obtained through the formation
of aluminum monofluoride. However, there has been very little thermodynamic analysis of the interactions of
the materials in the reaction zone and in the charge. This study gives special attention to the selection of
sintering additives and their effect on the removal of undesirable oxygen impurities during the synthesis of
aluminum nitride. The mix that was obtained for sintering can be used for the energy-efficient single-stage
production of aluminum-nitride finished products having excellent thermal conductivity.
Keywords: synthesis, aluminum nitride, thermodynamic analysis.
Aluminum nitride is a ceramic material that is much in
demand for research in electronics, electrical engineering,
heat engineering, machine construction, metallurgy, and nu-
clear energy thanks to such properties as high thermal con-
ductivity and electrical resistivity and a low coefficient of
linear thermal expansion. Its mechanical strength and resis
tance to thermal shock are greater than the corresponding
properties of corundum ceramics [1 – 3].
The properties of aluminum nitride depend to a signifi
cant degree on its purity. The presence of even a small
amount of oxygen in the material significantly reduces its
thermal conductivity (the most important property of alumi
num nitride) due to the formation of oxides and oxynitrides
on the surface of the grains. The articles [4, 5] presented a
detailed survey of the methods used to obtain aluminum
nitride and discussed each method’s positive and negative as
pects. For example, powders obtained by industrial meth
ods — carbothermic reduction and direct nitriding — are not
very pure. These processes require high synthesis tempera
tures, long holding times, and complicated equipment and
must be carried out in multiple stages. Other methods, such
as the production of aluminum nitride from organic com
pounds, high-temperature synthesis in an autoclave, or
self-propagating high-temperature synthesis also do not pro-
duce high-purity aluminum-nitride powder at low cost.
The authors of  have proposed a promising new tech-
nology for obtaining aluminum nitride. The technology is
based on an existing technology that produces high-purity
metallic aluminum powder with the aid of refining. The
study just cited included an explanation of the theoretical
foundation for the new method and a detailed thermody
namic analysis of the behavior of all of the components in
the charge used to synthesize aluminum nitride, the materials
of the furnace, and possible impurities. The authors also
made several recommendations for further development of
the equipment that is used to obtain ultradispersed high-pu
rity aluminum nitride.
Many researchers [7 – 9] have conducted studies focused
on the effect of fluoride additives on the sintering of alumi
num nitride and the effectiveness of replacing them with
commonly used oxides. Thus, it would be helpful to perform
a thermodynamic analysis of the possible introduction of ad
ditives that facilitate sintering during the synthesis stage in
order to keep even the most minute quantities of oxygen
from entering the aluminum nitride during mixing. In this ar
ticle, we examine the thermodynamic conditions in a sin
gle-stage gas-phase technology for synthesizing high-purity
aluminum nitride that is suited for further sintering in order
to obtain finished products.
Refractories and Industrial Ceramics Vol. 56, No. 1, May, 2015
1083-4877/15/05601-0097 © 2015 Springer Science+Business Media New York
Ural Federal University, Ekaterinburg, Russia.