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The evaporative decomposition of solutions method was used to form V 2 O 5 . Spraying above the congruent melting temperature of V 2 O 5 (690°C) resulted in dense spherical particles with a smooth surface. Spraying below the V 2 O 5 melting temperature yielded porous V 2 O 5 powder with a rough surface. Reduction of the V 2 O 5 to V 2 O 3 was done in a H 2 atmosphere. Spherical V 2 O 3 powder was attained when the reduction temperature was low enough to reduce the V 2 O 5 surface before partial sintering (necking) between V 2 O 5 particles occurred. The resulting V 2 O 3 particle size was smaller than the precursor V 2 O 5 powder as expected by the differences in densities between V 2 O 5 ( p = 3.36 g/cm 3 ) and V 2 O 3 ( p = 4.87 g/cm 3 ).
Sullivan et al. (Sat,) studied this question.