The preparation and properties of cobalt(II) tellurates

Cobalt(II) tellurates with the composition CoTeO 4 , CoTeO 4 .1/2 H 2 O and Co 3 TeO 6 were prepared. The first two are cubic with octahedral coordination around the cobalt atom and with TeO 6 octahedra joined at the edges. In Co 3 TeO 6 , which is isostructural with Ni 3 TeO 6 , the TeO 6 octahedra are isolated. At least one cobalt atom is tetrahedrally coordinated by oxygen atoms. The high values of the temperature independent paramagnetism, 11 m 3 kg -1 , and the Weiss constant, Θ = -64 K, indicate marked magnetic exchange interaction. The thermal decomposition of all three tellurates leads to formation of cobalt tellurates and finally to CoO and TeO 2 . At laboratory temperature all three substances are paramagnetic with μ eff values corresponding to divalent cobalt.