Plate Morphology. -Ellipsoid-like two-dimensional plates of the title compound are hydrothermally synthesized from EtOH solutions of Ca(NO 3 ) 2 and NbCl 5 (pH 11 adjusted with NH 4 OH, autoclave, 200°C, 24 h). The samples are characterized by powder XRD, SEM, TEM, fluorescence spectroscopy, and UV/VIS diffuse reflectance spectroscopy. Compared with CaNb 2 O 6 prepared by solid state reaction, the two-dimensional plates exhibit a much lower room temperature luminescence intensity and higher photocatalytic activity for the degradation of Rhodamine B dye solution under UV light irradiation. -(CHO, I.-S.; KIM, D. W.; CHO, C. M.; AN, J.-S.; ROH, H.-S.; HONG*, K. S.; Solid State Sci. 12 (2010) 6, 982-988,