FABRICATION OF HIGH-DENSITY QUARTZ CERAMICS:
RESEARCH AND PRACTICAL ASPECTS.
PART 3. SINTERING OF QUARTZ CERAMICS
E. I. Suzdal’tsev
Translated from Novye Ogneupory, No. 10, pp. 60 – 67, October, 2005.
Original article submitted April 25, 2005.
Results of a study of the sintering of quartz ceramics are presented and problems inherent in the production of
densely sintered minimally crystallized materials are outlined. The effective energy of activation of ceramic
sintering is closely controlled by the quality parameters of raw materials and process parameters. The activa
tion of sintering process is discussed and agents aiding in the preparation of densely sintered quartz ceramics
Sintering, as a major technological stage in the produc-
tion of ceramic materials, is a time-consuming process that
requires high temperatures for its implementation. During
sintering, the free space (voids and pores) become eliminated
owing to the intervention of the system’s components capa-
ble of developing a high mobility at elevated temperatures.
The free surface energy of the system tends to decrease ow
ing to the contraction of pore volume and phase boundaries.
In the course of the sintering process, grains of the initially
powder-like system cluster together to form compact aggre
In ceramics composed of quartz glass, the sintering be
comes complicated by cristobalitization, a process preferably
avoided, since the temperatures of sintering and intense ce
ramic crystallization lie close to each other. A certain amount
of crystalline phase formed in the quartz ceramic may lead to
a deterioration of its heat-resistant properties and eventually
to a complete loss of strength . Therefore it is important to
establish optimum process parameters and heat-treatment re
gimes that would allow one to obtain components of suffi
ciently high density (low porosity) with a minimum amount
A theory for sintering of amorphous powders was pro
posed by Frenkel  and later was confirmed in the litera
ture. Thus, in , the rates of contact formation between a
glass sphere and a substrate and between two glass spheres
were measured and the rate of contact area was shown to be a
linear function of time, in agreement with Frenkel’s formula
for the initial stage of sintering,
where Y is the contact area radius, s is the surface tension,
t is the time, h is the viscosity, and r
is the original radius of
a glass sphere.
For the final sintering stage, Frenkel’ proposed an equa
tion which was derived from a model for a single spherical
pore placed in a viscous infinite medium:
where a is the pore radius at the instant of time t and b is a
coefficient which is 3/4 for a spherical pore and 1 for a cy
The validity of this formula was likewise verified. In ,
the rate of change of the diameter of a capillary heated to the
softening temperature was considered and shown to be a li
near function of time.
Based on Frenkel’s sintering theory, MacKenzie and
Shuttleworth  proposed a model involving multiple, rather
Refractories and Industrial Ceramics Vol. 46, No. 6, 2005
1083-4877/05/4606-0384 © 2005 Springer Science+Business Media, Inc.
Tekhnologiya Research and Production Enterprise, Obninsk,
Kaluga Region, Russia.