Brillouin scattering of urea-doped thiourea

Urea (CO(NH2)(2))-doped thiourea (CS(NH2)(2)) crystals were grown by the evaporation method. The values for the x concentration for [CS(NH2)(2)](100-x)[CO(NH2)(2)](x) crystals were determined by a chemical analysis of oxygen and sulfur and checked far complementarity with dielectric constants and Brillouin shifts. The x less than or equal to 1 mol% was found for any ratio of mixed reagents. The temperature dependence of Brillouin shifts of the longitudinal acoustic phonon (C-33) in the x approximate to 1.1 crystal was similar to that of pure thiourea. However, the sudden jump in the incommensurate phase may indicate the escape of CO(NH2)(2) as an impurity due to loose coupling.