Fig. 2a shows the SEM micrograph on the SrMnO3 powder after
heat treatment at 1000 C for 10 h. Generally, the sample is characterized
by a fine granulation and a porous structure. The particles
clustering into mini- or macro-agglomerations with irregular
shapes and sizes is evident. The SrMnO3 particles being small, a
tendency towards agglomerations can be noticed. The average
grain size is above 100 nm. One can also remark the presence of
the grain shape going from hexagonal faceted to rounded crystallites,
and of large pores distributed along the grain agglomerations.
The crystallinity of the powder heat treated at 1000 C for 10 h
was confirmed by the energy dispersive X-ray spectra (EDX). The
obtained chemical elemental composition is typical for this perovskite
(any foreign element is absent). Fig. 2b presents the EDX
spectrum for this powder. Moreover, the composition of the sample
is similar to the nominal one, ABO3, i.e. the A/(A + B) or B/
(A + B) ratio is close to 0.5 (where A is Sr at.%, and B is Mn at.%).
The microstructure plays a predominant role in the catalytic
process. The method we have used offers the advantage of producing
nanosized and homogeneous particles with precise stoichiometry.
The achievement of perovskites with high specific surface
areas (2.20 m2/g) and nanosized particles (88.9 nm) is a priority
in the performance of a ceramic catalyst. In general, high surface
areas imply small particle sizes. The smaller the particle size, the