Metathesis routes to lanthanide pnictides

Abstract

Reaction of Na₃As or Na₃Sb with anhydrous LnCl₃(Ln = Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tb, Yb) at 500–900 °C in sealed Pyrex or quartz ampoules produces crystalline lanthanide arsenides or stibides (LnAs, LnSb, Eu₂Sb₃, Yb₅Sb₄), in good yields (70–90%), via, metathesis reactions. Mixed lanthanide arsenides and stibides, Ln_0.5Ln′_0.5E, (LnLn′= DyEr, NdPr; E = As; LnLn′= LaY, TbHo, TbEr, LaHo and PrHo; E = Sb) are made in a similar fashion by combining mixed lanthanide halide powders with Na₃As or Na₃Sb and initiating the reaction at 800 °C. Solid solutions of LnAs_xP_y and LnSb_xAs_y(Ln = Dy, Sm, Tb; x+y= 1) are made analogously using Na₃As_xP_y and Na₃Sb_xAs_y as starting materials. Lanthanide bismuthides (LnBi), can be made from LnCl₃ and Na₃Bi; however, decomposition to Ln metal and bismuth occurs on trituration with methanol. The lanthanide arsenides, lanthanide stibides, mixed lanthanide arsenides and mixed lanthanide pnictides were characterised by X-ray powder diffraction (XRD), microanalysis, scanning electron microscopy (SEM), energy dispersive X-rays analysis (EDXA), FTIR and magnetic-moment measurements.