Abstract
Single crystals of CaW1−xMoxO4 scheelite-powellite solid solutions (x = 0.0, 0.03, 0.08, 0.2, 0.3, 0.5, 0.8, and 1.0) were synthesized using a melting method. The light emission spectra of the solid solutions were measured using a JASCO FP-8300 fluorescence spectrometer. The maximum fluorescence peak at 419 nm in the CaWO4 scheelite end-member greatly decreases in intensity and shifts its peak position to 451 nm with only 3% Mo substitution. The change in near-ultraviolet light emission intensity at 292 and 301 nm are more moderate than those in the strong peak at 419 nm. The tendency of change in intensity and wavelength shift due to the Mo substitution differs among these fluorescence peaks. Single crystal X-ray diffraction experiments for the CaW1−xMoxO4 solid solutions (x = 0.0, 0.2, 0.3, 0.5, 0.8, and 1.0) were carried out using a Rigaku Super-Nova Single source at offset/far HyPix3000 diffractometer. The R1 index for CaW1−xMoxO4 solid solutions were convergent to 1.22-1.71% using anisotropic temperature factors. The expansion of the c-axis and shrinkage of the unit cell volume were induced with an increase in Mo content. The significant increase in the angle ∡Ocloser-Ca-Ocloser was directly related to the expansion of the c-axis. The Debye temperature ΘD for Ca, W, and O atoms in CaWO4 were 381, 198, and 534 K, respectively. The obtained ΘD for Ca, Mo, and O atoms in CaMoO4 were 363, 257, and 503 K, respectively. The phonon density of states estimated from the lattice dynamics calculations coincided with the observed ΘD values.
