Isomorphous substitution in non-linear optical KTiOPO4. Time-of-flight neutron powder diffraction study of K0.5Rb0.5TiOPO4

Abstract

Rubidium is ion-exchanged into non-linear KTiOPO₄ in the preparation of optical waveguide devices. The structure of K_0.5Rb_0.5TiOPO₄ has been determined by Rietveld analysis of time-of-flight neutron powder diffraction data: Pn2₁a, a= 12.8961(10)Å, b= 10.5929(8)Å, c= 6.4299(5)Å; R_P= 3.45%, wR_P= 5.50%. It is found that substitution of K by Rb takes place preferentially at the K(2) site, which contains 71% Rb, rather than the K(1) site, which contains only 29%.