Synthesis and structural characterisation of new ettringite and thaumasite type phases: Ca6[Ga(OH)6•12H2O]2(SO4)3•2H2O and Ca6[M(OH)6•12H2O]2(SO4)2(CO3)2, M = Mn, Sn
journal contributionposted on 30.07.2014, 09:45 authored by Rachel L. Norman, Sandie DannSandie Dann, Simon HoggSimon Hogg, Caroline Kirk
Investigations into the formation of new ettringite-type phases with a range of trivalent and tetravalent cations were carried out to further study the potential this structure type has to incorporate cations covering a range of ionic radii (0.53–0.69 Å). We report the synthesis and structural characterisation of a new ettringite-type phase, Ca6[Ga(OH)6•12H2O]2(SO4)3•2H2O, which was indexed in space group P31c with the unit cell parameters a = 11.202(2) Å, c = 21.797(3) Å and two new thaumasite-type phases Ca6[M(OH)6•12H2O]2(SO4)2(CO3)2, M = Mn, Sn which were indexed in space group P63 with the unit cell parameters a = 11.071(5) Å, c = 21.156(8) Å and a = 11.066(1) Å, c = 22.420(1) Å respectively. These new phases show the versatility of the ettringite family of structures to tolerate a large range of cation sizes on the octahedral M site and highlights the preference of tetravalent cations to crystallise with the thaumasite structure over the ettringite structure.
CK would like to acknowledge financial support from The Natural History Museum and WestChem.