Synthesis and crystal structure of three silver indium double phosphates

Three new silver indium double phosphates Ag3In(PO4)2 (I), β-(II) and α-Ag3In2(PO4)3 (III) were synthesized by solid state method (I and II—700 °C, III—900 °C). Compounds I and II crystallize into a monoclinic system (I—sp. gr. C2/m  , Z=2Z=2, a=8.7037(1)Åa=8.7037(1)Å, b=5.4884(1)Åb=5.4884(1)Å, c=7.3404(1)Åc=7.3404(1)Å, β=93.897(1)°β=93.897(1)°; II—sp. gr. C2/c  , Z=4Z=4, a=12.6305(1)Åa=12.6305(1)Å, b=12.8549(1)Åb=12.8549(1)Å, c=6.5989(1)Åc=6.5989(1)Å, β=113.842(1)°β=113.842(1)°), and compound III crystallize into a hexagonal system (sp. gr. R-3c  , Z=6Z=6, a=8.9943(1)Åa=8.9943(1)Å, c=22.7134(1)Åc=22.7134(1)Å). Their crystal structures were determined by the Rietveld analysis (I—Rp=6.47Rp=6.47, Rwp=8.54Rwp=8.54; II—Rp=5.67Rp=5.67, Rwp=6.40Rwp=6.40; III—Rp=7.30Rp=7.30, Rwp=9.91Rwp=9.91). Structure of Ag3In(PO4)2 is related to the sodium chromate structure type and is isotypic to α-Na3In(PO4)2. The polymorphous modifications of β- and α-Ag3In2(PO4)3 are isostructural to sodium analogs (β- and α-Na3In2(PO4)3) and are related to alluaudite (II) and NASICON (III) structure types. Compounds I and II are not stable at temperature above 850 °C. Ag3In(PO4)2 is decomposed providing silver orthophosphate Ag3PO4 and α-Ag3In2(PO4)2. β-Ag3In2(PO4)3 is transformed to α-Ag3In2(PO4)3.

Graphical abstractThe dimer block In2O10 with PO4-tetrahedra in α-Ag3In2 (PO4)3.Figure optionsDownload full-size imageDownload as PowerPoint slide