A 2 BiI 5 O 15 (A = K + or Rb + ): two new promising nonlinear optical materials containing [I 3 O 9 ] 3− bridging anionic groups

K 2 BiI 5 O 15 and Rb 2 BiI 5 O 15 are synthesized and contain a unique [I 3 O 9 ] 3− bridging anionic group. Their powders show phase-matchable SHG effects 3 times that of KDP and the laser damage thresholds of 84 and 72 MW cm −2 , plus wide transparent range and good thermal stability.