Synthesis, crystal structure and luminescent properties of a quinary borate-phosphate compound CsNa2Dy2(BO3)(PO4)2

Borate-phosphates exhibit a wide range of compositional and structural diversity, making them ideal hosts for luminescent materials. In this work, a new borate-phosphate compound CsNa2Dy2(BO3)(PO4)2 has been prepared under high temperature solution growth method. It crystallizes in an orthorhombic space group Cmcm with the following lattice parameters determined by single-crystal X-ray diffraction: a = 6.9709(5), b = 14.9699(11), c = 10.6480(8) Å, z = 4. Its structure contains isolated BO3 planar triangles and PO4 tetrahedra, which are interconnected by Cs+, Na+ and Dy3+ ions. Solid solutions of CsNa2Y2(1−x)Dy2x (BO3)(PO4)2 (x = 0 − 0.08) are prepared and exhibit a yellow emissive luminescence by near-UV excitation due to the 4F9/2 → 6H(13/2, 15/2) transitions of Dy3+. The optimized concentration of Dy3+ is x = 0.01, and if over this critical value, the luminescent intensity will decrease due to concentration quenching. The Commission International de L’Eclairage (CIE) coordinates for CsNa2Y1.98Dy0.02(BO3)(PO4)2 are (x = 0.377, y = 0.404), corresponding to yellow color. The prepared phosphor may serve as a yellow phosphor for NUV-excited LEDs.