SEARCH

SEARCH BY CITATION

Keywords:

  • crystal growth;
  • kinetics;
  • polyoxovanadates;
  • solvothermal synthesis;
  • X-ray diffraction

Abstract

The formation of the antimonato polyoxovanadates [V14Sb8(C6H15N3)4O42(H2O)]4H2O (1), (C6H17N3)2[V15Sb6(C6H15N3)2O42(H2O)] 2.5H2O (2), {C6H15N3}4[V16Sb4O42] 2H2O (3) (C6H15N3=1-(2-aminoethyl)piperazine, AEP) has been studied under solvothermal conditions by using in situ energy dispersive X-ray diffraction (EDRXD). The syntheses were performed with an identical ratio for Sb2O3 and NH4VO3. If the reactions slurries are not stirred during the solvothermal reaction and by applying 70–75 % amine concentration, the products contain all three compounds, whereas 3 is observed at 80 %. Under stirring conditions, variation of the concentration of AEP led to crystallization of the three different compounds at distinct concentrations, that is, 1 is formed at 75 %, 1 and 2 between 75 and 80 % and 3 at 80 %. At an amine concentration of 77.5 %, first reflections of 2 occurred and at later stages, compound 1 started to crystallize. The sample with the lowest number of VIV species was formed at the lowest amine concentration, whereas crystallization of 3 required the highest concentration. The formation of the compounds occurred without crystalline intermediates and/or precursors. With increasing reaction temperature, the incubation time was significantly reduced.