Synthesis, Structural Characterization, and Physical Properties of the New Transition Metal Oxyselenide Ce₂O₂ZnSe₂

The quaternary transition metal oxyselenide Ce2O2ZnSe2 has been shown to adopt a ZrCuSiAs-related structure with Zn(2+) cations in a new ordered arrangement within [ZnSe2](2-) layers. The color of the compound changes as a function of cell volume, which can vary by ∼0.4% under different synthetic conditions. At the highest, intermediate, and lowest cell volumes, the color is yellow-ochre, brown, and black, respectively. The decreased volume is attributed to oxidation of Ce from 3+ to 4+, the extent of which can be controlled by synthetic conditions. Ce2O2ZnSe2 is a semiconductor at all cell volumes with experimental optical band gaps of 2.2, 1.4, and 1.3 eV for high, intermediate, and low cell volume samples, respectively. SQUID measurements show Ce2O2ZnSe2 to be paramagnetic from 2 to 300 K with a negative Weiss temperature of θ = -10 K, suggesting weak antiferromagnetic interactions.