Structure of two new borates YCa3(AlO)3(BO3)4 and YCa3(GaO)3(BO3)4

By replacing Mn in YCa3(MnO)3(BO3)4 with trivalent Al and Ga, two new borates with the compositions of YCa3(MO)3(BO3)4 (M=Al, Ga) were prepared by solid-state reaction. Structure refinements from X-ray powder diffraction data revealed that both of them are isostructural to gaudefroyite with a hexagonal space group P63/m  . Cell parameters of a=10.38775(13)Åa=10.38775(13)Å, c=5.69198(10)Åc=5.69198(10)Å for the Al-containing compound and a=10.5167(3)Åa=10.5167(3)Å, c=5.8146(2)Åc=5.8146(2)Å for the Ga analog were obtained from the refinements. The structure is constituted of AlO6 or GaO6 octahedral chains interconnected by BO3 groups in the ab plane to form a Kagomé-type lattice, leaving trigonal and apatite-like tunnels. It is found that most rare-earth and Cr, Mn ions can be substituted into the Y3+ and M3+ sites, respectively, and the preference of rare-earth ions to locate in the trigonal tunnel is correlated to the sizes of the M3+ ions.

YCa3(MO)3(BO3)4 structure is constructed by MO6 edge-shared chains interconnected by BO3 groups with Y and Ca atoms occupying the triagonal and apatite-like tunnels.Figure optionsDownload as PowerPoint slide