SCIENTIFIC RESEARCH AND DEVELOPMENT
NEW PERICLASE-MAGNESIUM ALUMINATE SPINEL REFRACTORIES
FROM SINTERED HIGH-PURITY DEAD BURNED MAGNESITE
AND NEW VARIOUS PRESYNTHESIZED SPINEL-BASED COMPOSITIONS.
II. COMPOSITIONAL VARIATION BETWEEN COEXISTING SPINEL,
PERICLASE, AND Ca-SILICATE AND Ca-ALUMINATE PHASES
IN MAGNESIA SPINEL REFRACTORIES AND IN THEIR
P. G. Lampropoulou,
C. G. Katagas,
and I. Iliopoulos
Translated from Novye Ogneupory, No. 11, pp. 34 – 48, November, 2012.
Original article submitted May 17, 2012
The chemistry and distribution of phases formed in a set of six laboratory-prepared magnesia-magnesium
aluminate spinel ceramics and in three of their precursor spinel-based compositions, sintered at 1600°C and
1760°C respectively, are examined and compared. The evaluation of the results is the basis for the industry de-
sign of magnesia spinel refractories for new advanced applications. In each type of the materials, the spinel
phases formed under their firing temperatures seem to have a strong preference for the normal structure.
Cracked and noncracked domains in periclase crystals from spinel-based compositions is probably facilitated
by differences in the thermal expansion coefficient of periclase crystals having domains differing in their
contents. Periclase and spinel mixtures at lower temperatures (1600°C) involved reactions leading to
the formation of different periclase s.s and spinel s.s, which depart clearly from equilibrium assemblages. Mi
nor amounts of stoichiometric Ca-silicate and Ca-aluminate phases were formed in all materials.
Keywords: spinels, MgO, silicate, phase composition, sintering.
Most of the studies concerned with magnesia-spinel
refractories focus mainly on their physical and technological
properties related to their microstructures. Such studies on
the physical properties of various magnesia-spinel based
compositions and their microstructures in relation to their
densification parameters and refractory resistance, as well as
on different synthesis routes [1 – 7] and on the effects of dif
ferent additives on the development of spinel based composi
tions with improved sintered properties, have been published
by many researchers [e.g., 8 – 12].
It is now well established that magnesia-spinel refracto
ries derived from pure raw materials with a high degree of
direct bonding of MgO-MgO and MgO-spinel grains, and
with low amounts of low-melting silicate phases, exhibit
high hot temperature strength, improved resistance to slag at
tack, and dimensional stability at high temperatures [13, 14].
Nowadays, the need for a detailed study of magne
sia-spinel materials is further underscored in order to pro
mote their uses in many other fields such as in catalysis, opti
cal ceramics, and humidity sensors [15 – 19] under the
framework of “green policies” that are widely sought by or
ganizations and governments. Newly developed magne
sium-aluminate spinel ceramics, for instance, appear to meet
the requirements for geological time-period disposal of
high-level nuclear and hazardous wastes [20, 21]. In a com
panion paper to this study  we report details on the labo
ratory synthesis, mineralogical composition, microstructure,
and property evaluation of a set of six rebonded magne
sia-magnesium aluminate spinel refractories containing vari
Refractories and Industrial Ceramics Vol. 53, No. 6, March, 2013
1083-4877/13/05306-0364 © 2013 Springer Science+Business Media New York
Department of Geology, University of Patras, Patras, Greece.