CRYSTALLIZATION OF LNCU(2)O(4) (LN=LA, ND, SM, EU, GD, DY, HO, Y, ER)FROM HYDROXIDE MELTS - SYNTHESIS AND STRUCTURE

The synthesis and structure of LnCu(2)O(4) with Ln = La, Nd, Sm, Eu, G d, Dy, Ho, Y, and Er are reported. These cuprates were synthesized by precipitation from NaOK/KOH at 350-400 degrees C under ambient conditi ons. The effects of changing the relative amounts of NaOH and KOH, the quantities of the starting reagents, the reaction temperature, and th e time at which the reagents were added on the yield, purity, and crys tallinity of LnCu(2)O(4) are described. Generally, the formation of Ln Cu(2)O(4) is favored in dry, highly oxidizing melts with large quantit ies of dissolved reactants. Powder X-ray diffraction data were used to refine the structure of the various analogues using Rietveld profile analysis. The lattice parameters and average Ln-O distances decrease w ith decreasing size of the lanthanide ion. The average Cu-O bond dista nces, on the other hand, do not significantly change with the size of the lanthanide ion.