A new potassium rare earth oxyborate K2La2(BO3)2O

Abstract A series of potassium rare earth oxyborates, K 2 RE 2 (BO 3 ) 2 O (RE = La, Nd, Sm and Eu), have been synthesized. Single crystal of the first member of the series, K 2 La 2 (BO 3 ) 2 O, has been grown by the flux method. Its structure, determined by single crystal X-ray diffraction, shows that it belongs to the monoclinic system, space group P2 1 /c with unit cell parameters of a  = 11.422(2) A, b  = 6.6803(13) A, c  = 10.813(2) A, β  = 17.23(3)° and Z  = 4. Optical transmission spectrum shows that the K 2 La 2 (BO 3 ) 2 O crystal is highly transparent from 215 nm to 2750 nm.