Crystal structure and Eu3+/Tb3+ doped luminescent properties of a new borate Ba3BiB9O18

Undoped and doped either by Eu3+ or Tb3+ bismuth borate Ba3BiB9O18 was structurally characterized and analyzed by fluorescence spectroscopy. Belonging to synthetic borate member of the family Ba3XB9O18, layers of planar triangular B3O6 groups connecting with deformed BaO6 hexagons are interleaved by 9-coordinate Ba atoms, and 6-coordinate Bi atoms. Its crystal structure was determined and refined from powder X-ray diffraction data by the Rietveld method and the results showed that Ba3BiB9O18 belongs to space group P63/m with unit cell dimensions of a = 7.1999(2) Å, c = 17.3567(6) Å, and z = 2. Curves of differential thermal analysis and thermogravimetric analysis showed that Ba3BiB9O18 is a congruent melting compound and chemically stable above 728 °C. Ba3Bi1−xEuxB9O18 and Ba3Bi1−xTbxB9O18 form a continuous solid solution from x = 0.01 to x = 0.9. The ultraviolet excited photoluminescence intensity increased with both Eu3+ and Tb3+ concentration in the matrix of Ba3BiB9O18. There may be an interesting correlation between spectroscopic properties and lattice structural features of doped Ba3BiB9O18.