Thermal behaviour and kinetics of formation reaction of the synthetic analogue of pääkkonenite, Sb2AsS2
Bernardini, Gian Piero; Borrini, Daniele; Corsini, Fernando; Danti, Cοstanza; Guarini, Giulio G.T.; Mazzetti, Giuseppe; Rosso, Fabio
European Journal of Mineralogy Volume 8 Number 3 (1996), p. 639 - 648
published: Jun 17, 1996
manuscript accepted: Jan 15, 1996
manuscript received: Aug 13, 1995
ArtNo. ESP147050803014, Price: 29.00 €
Abstract The thermal behaviour and kinetics of formation reaction of the synthetic analogue of pääkkonenite (SB2ASS2), has been investigated by means of D.T.A. and D.T.P. procedures. Whereas a new, redefined X-ray diffraction pattern is given, all other optical and chemical characteristics of the synthetic compound match perfectly those of the natural Sb2AsS2. The Sb2AsS2 compound, which melts incongruently at 530°C to give stibarsen and a stibnite-like melt, may be easily synthesised either through a completely controlled solid-state reaction or through a combination of solid-state and solid-melt reactions (as a function of the scan rate of the D.T.P. experiments). The experimental data obtained from the exothermic features of the D.T.P. thermograms fit kinetic equations for a diffusion-controlled process; the activation energy, evaluated using an Arrhenius formalism, agrees with that reported for diffusion processes in other minerals. The detailed mechanism of the solid-state reaction has not been deciphered, but the similarity of Sb2AsS2 structure with that of stibnite explains the small amount of energy required for its formation.