It was found that the non-isothermal devitrification
of glasses of composition CaO–La2O3–SiO2 exhibited peculiar
characteristics [2]. These devitrify through a surface nucleation
mechanism. However,since in the temperature range of efficient
crystal growth,softening and sintering occur,surface nuclei
behave virtually as bulk nuclei [3–4]. From another perspective,
La–Si–O–N [5–6], La–Si–Al–O–N [7] and La–Ca–Si–Al–O–N [8] oxy-
nitride glasses have since been prepared in systems,and some
evidence shows that as the La content in creases,Young's modulus,
hardness, glass transition temperature and viscosity increases
with increase in cationic field strength(CFS).As is known to all,
crystallization heat-treatments on oxynitride glasses can lead to
significant improvements in mechanical properties.However,very
little literature on the crystallization of the La-containing oxyni-
tride glasses has been reported [9]. It is very difficult that the
oxynitride glass crystallize to form N-containing solid solutions
after heat-treatment.Most o fthe content of nitrogen generally
remains in the residual glass.As per our knowledge,thecrystal-
lization of β-Si3N4 from silicate oxynitride glasses at after heat-
treatment has never been reported.Low-temperature sintering
behavior of the Si3N4 ceramics and chemical and thermal properties
of the obtained Si3N4 ceramics are reported in some studies [10–12].