SYNTHESIS AND PROPERTIES OF A NEW BETA-POLYMORPH OF LI3CRO4

Beta-Li3CrO4, isostructural with beta-Li3PO4, has been synthesized by two routes. Reaction of Li2CO3 and Cr2O3 in a 5:1 mole ratio in flowing Ar at 800-degrees-C yields beta-Li3CrO4 with a small amount of Li2O. The Li2CO3 seems to have two functions. It is an essential reactant and acts as a novel oxidant, promoting conversion of Cr(III) to Cr(V). Reaction of Li2CO3 and CrO3 in a 3:1 mole ratio in flowing Ar also gives phase-pure beta-Li3CrO4. Magnetic measurements show Curie-Weiss behaviour in the range 20-300 K with a magnetic moment of 1.70 mu(B) consistent with Cr(V) in tetrahedral coordination. Conductivity measurements show a modest level of electronic conduction.