Syntheses, crystal structure and luminescence properties of the novel isostructural KSrR(BO3)2 with RÂ =Â Y, Yb, Tb

Three new rare-earth based orthoborates KSrR(BO3)2, with R = Y, Tb, Yb were synthesized by solid-state reaction method. Single crystals of KSrR(BO3)2 were obtained by spontaneous crystallization using selected flux. Single-crystal X-ray diffraction measurements reveal that KSrY(BO3)2 crystallizes in monoclinic space group P21/m with cell parameters of a = 9.2743(3) Å, b = 5.35919(12) Å, c = 6.5749(2) Å, and β = 117.682(4)°. Distinctive feature of studied borates structure is the close-packed composite of anion-cation (K,Sr)(BO3) layers. The two-layer {Y[KSr(BO3)2]} package is the base building block for this structure, with one package on c-period. The comparison of the structures of Ba2Mg(BO3)2, BaNaY(BO3)2, KBaY(BO3)2 and KSrY(BO3)2 is discussed. The photoluminescence properties of the synthesized borate KSrTb(BO)3 under UV excitation have been investigated in a detail.