Temperature dependence of the polarized electronic absorption spectra of olivines. Part II?Cobalt-containing olivines

Effect of sol–gel method on colour properties of the classical cobalt olivine (Co2SiO4) ceramic pigment

“…These assignments are in good agreement with those reported in earlier works [15][16][17]. Furthermore, spin-forbidden d-d transitions to the other excited terms could be contributing to the absorbance at still higher energies (up to 300 nm) in the near-UV region [17]. However, these bands as well as those in NIR region (900-1600 nm) do not contribute to the absorption in the borders of visible zone and thus, they do not have any optical effect.…”

“…For the infrared region, the bands centred at around 1300 (M1 sites) and 1560 nm (M2 sites) correspond to the ν 1 spin-allowed transitions to the excited term 4 T 2 (F). These assignments are in good agreement with those reported in earlier works [15][16][17]. Furthermore, spin-forbidden d-d transitions to the other excited terms could be contributing to the absorbance at still higher energies (up to 300 nm) in the near-UV region [17].…”

Reduced radiative conductivity of low spin FeO6-octahedra in FeCO3 at high pressure and temperature

“…The red-shift is likely due to the thermal expansion as the energy separation between the t 2g and e g orbitals is inversely proportional to the fifth power of the metal-ligand distance (Burns, 1993). Intensity variations of CF bands with temperature reported in the literature show a less regular behavior (Shankland et al, 1979;Fukao et al, 1968;Goncharov et al, 2008;Ullrich et al, 2002Ullrich et al, , 2004Thomas et al, 2012;Taran et al, 1994), but often may be understood in terms of temperature-induced changes in the CF symmetry (Taran and Langer, 2001) lifting the Laporte selection rule, which impedes electron transfer among the same parity states (e.g. d-d transitions).…”

Sol gel synthesis of forsterite, M-doped forsterite (M=Ni, Co) solid solutions and their use as ceramic pigments

“…These assignments were in good agreement with reported earlier works. 32,13,33 Once again, the optical spectra of all Mg 2−x Co x SiO 4 pigments indicate that their violet color is due to the d-d transitions within Co 2+ ions in the forsterite octahedral sites and results from absorption over all visible spectra except the violet region around 400-450 nm. The Co 2+ preference for olivine M1 sites confirmed by several works based on X-ray structure refinement of a synthetic Mg-Co 2+ olivine (see, Ghose and Wan 34 ; Bostrom 35 ), is less evident from crystal field spectra of Mg 2−x Co x SiO 4 .…”