PHASE RELATIONS IN THE K_3Ln(PO_4)_2-K_3Ln(VO_4)_2(Ln=la,Gd) SYSTEMS

摘要

Phase relations in the K_3Ln(PO_4)_2-K_3Ln(VO_4)_2(Ln=La,Gd) systems at 770℃ were studied by x-ray diffraction analysis .single-phase K_3Ln(PO_4)x(VO_4)_2-x(x=0-0.2) materials were prepared by solid-state reactions between Ln_2O_3,K_2CO_3,KH_2PO_4,and NH_4VO_3 in the course of steplide heating from 70 to 770℃. Both systems were shown to contain a continuous series of solid solutions with the arcanite structure. The unit-cell parameters and volume of the solid solutions were determined. The materials were found to pick up water vapor and CO_2 in amounts dependent on their composition.