Synthesis, crystal structure of LiCaRE 5(BO3)6 (RE = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) and Eu3+ luminescence in LiCaRE 5(BO3)6 (RE = Gd, Y, Lu)

Highlights: • LiCaRE₅(BO₃)₆ were synthesized by high temperature solid state reactions. • High quality powder XRD data confirm the phase purity. • Structure details were obtained by careful Rietveld refinements. • Ca²⁺ co-occupy with the rare earth cations at M1 and M3 sites. • LiCa(RE_0.95Eu_0.05)₅(BO₃)₆ (RE=Gd, Y, Lu) gives a bright red-orange emission. A series of rare earth polyborate with the general formula LiCaRE₅(BO₃)₆ (RE=Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) were synthesized by high temperature solid state reactions. In literature, the Cd-analogues and LiCaTb₅(BO₃)₆ were reported, here Rietveld refinements were performed on high quality powder X-ray diffraction data and the crystallographic parameters were obtained for the title compounds. Eu³⁺-luminescence in LiCaRE₅(BO₃)₆ (RE=Gd, Y, Lu) were characterized. Eu³⁺ activators were doped into both the close-to-centrosymmetric and strongly-distorted coordination environments. Overall, bright orange-red emission can be observed with a slight increase of the red-to-orange (R/O) ratio with RE³⁺ ionic radius increases.