METATHETICAL SYNTHESIS OF BINARY AND TERNARY ANTIFERROMAGNETIC GADOLINIUM PNICTIDES (P, AS, AND SB)

Polycrystalline powders of new ternary phases and well-known binary '' III-V'' type antiferromagnetic gadolinium pnictides have beep prepared in seconds by rapid solid-state metathesis (exchange) reactions: GdI3 + Na(3)Pn --> GdPn + 3NaI (where Pn = pnictogen = P, As, Sb, or PxAs1 -x). Following thorough mixing of the precursors, the reactions are in itiated by local heating with a hot filament and the products are easi ly isolated by washing with methanol and water. The effectiveness of t he solid-state metathesis (SSM) process is shown by comparing the prec ursor reaction products-to these generated by the direct combination o f the elements at elevated temperatures (1000 degrees C for 100 h). Ch aracterization techniques include powder X-ray diffraction (XRD), magn etic susceptibility, scanning electron microscopy, and energy dispersi ve X-ray analysis (EDX). The rapidly generated SSM products are single -phase, antiferromagnetic, XRD- and EDX-pure powders, comparable to th e compounds prepared by heating the elements together for several days . Slight traces of ferromagnetic gadolinium, as revealed by field-depe ndent magnetization, are removed and the average particle size is incr eased by a 12 h anneal at 1000 degrees C. The new gadolinium phosphide -arsenide solid solutions display magnetic constants (T-N and Theta(p) ) intermediate between those of their binary progenitors.