Phonon characteristics and intrinsic properties of phase-pure CaMoO4 microwave dielectric ceramic

Microstructural and electrical changes in Ca0.9R0.1CeNbMoO8 (R = Y, Sm, Nd, La) ceramics induced by rare‐earth ion doping

“…CaMoO 4 is a scheelite structure belonging to the tetragonal I4 1 /a ( a = b = 5.222 Å, c = 11.425 Å and α = β = γ = 90°) space group 23 . The weak binding between Ca 2+ ions and [MoO 4 ] tetrahedral units in CaMoO 4 structure provides conditions for the substitution of Ce ions for Ca 2+ 20 . At high‐temperatures (≥1073 K), both CaMoO 4 and CeNbO 4 have a tetragonal structure.…”

“…the other six belong to internal modes. 19,20 The vibrational external mode is related to the lattice phonon, which corresponds to the motion of [CaO 8 ] clusters and rigid [MoO 4 ] clusters unit. The mode corresponds to the vibration in the [MoO 4 ] cluster unit.…”

“…23 The weak binding between Ca 2+ ions and [MoO 4 ] tetrahedral units in CaMoO 4 structure provides conditions for the substitution of Ce ions for Ca 2+ . 20 ] clusters coordinated with it, thus inhibiting the transformation of CeNbO 4 from tetragonal to monoclinic during cooling, which is why CaCeNbMoO 8 ceramics only show substitutional solid solution having scheelite structure. By measuring the density of ceramics under the same preparation conditions, it is found that ρ (CaMoO4) < ρ (CaCeNbMoO8) < ρ (CeNbO4) (ρ (CaMoO4) = 4.11 g/cm 3 , ρ (CaCeNbMoO8) = 4.83 g/cm 3 , ρ (CeNbO4) = 5.69 g/cm 3 ).…”

Synthesis, characterization, and photocatalytic CO2 reduction evaluation of the CaWxMo1−xO4 (x = 0–1) solid solution

“…53 Finally, the signatures of calcium molybdate are at 792, 844, and 876 cm À1 , which are associated with symmetric stretching Mo-O and bending Mo-O modes. 52 However, in bare CaWO 4 (spectrum g), only 7 active vibration modes were identified. In this context, the internal vibration modes of CaWO 4 are associated with [WO 4 ] 2À cluster vibrations in the lattice.…”

“…In bare CaMoO 4 (spectrum a), 8 vibration modes were observed in the analyzed interval assigned to active A g , B g , and E g signals. According to some reports, 51,52 all of them are assorted into internal and external modes of vibrations. The internal vibrations correspond to the oscillations inside [MoO 4 ] 2À units, while the external vibrations agree with the motion of Ca 2+ in the rigid molecular unit.…”