Novel Sr3Bi2(BO3)4:Eu3+ red phosphor: Synthesis, crystal structure, luminescent and thermal properties

Abstract

Novel compound, Sr3Bi2(BO3)4, and Sr3Bi2(BO3)4:Eu3+ series were firstly synthesized by crystallization from a melt. The crystal structures of Sr3Bi2(BO3)4 and Sr3Bi1.66Eu0.34(BO3)4 borates were refined from single crystal X-ray diffraction data to R1 = 0.051 and 0.067, respectively. Sr3Bi2(BO3)4 borate crystallizes in the orthorhombic space group Pnma, a = 7.5107 (5), b = 16.2737 (11), c = 8.8163 (5) Å, V = 1077.59 (12) Å3, Z = 4. These compounds are isotypical to those of A3REE2(BO3)4 family, A = Ca, Sr, Ba. Crystal structure consists of isolated BO3 triangles and three independent M1O8, M2O8 and M3O8 polyhedra, which are connected by corners and edges forming the framework. The distribution of Sr and Bi atoms is partially disordered over M1-M3 positions. Thermal transformations of Sr3Bi2(BO3)4:Eu3+ series were studied by DSC and TG, powder HTXRD, thermal expansion of Sr3Bi2(BO3)4 borate was investigated by powder HTXRD. The emission spectra of Sr3Bi2(BO3)4:Eu3+ show characteristic lines attributed to the intra-configurational 4f-4f transitions in Eu3+ ions. Sr3(Bi0.85Eu0.15)2(BO3)4:Eu3+ demonstrates the strongest luminescent intensity among studied in this work borates. It can be concluded that Sr3Bi2(BO3)4:Eu3+ is a promising red phosphor.