MIXED CHROMIUM (II) TITANIUM (III) PHOSPHATES: CRYSTAL GROWTH, STRUCTURES AND ELECTRONIC ABSORPTION SPECTRA
2005 年 19 巻 p. 54-59
詳細
2005 年 19 巻 p. 54-59
The new quaternary phosphates Cr3Ti4(PO4)6 (dark brown, transparent crystals, Fe7(PO4)6 structure type), CrTi2(P2O7)2-black (lavender coloured powder), and CrTi2(P2O7)2-purple (pink powder) have been synthesized and crystallized by means of chemical vapour transport in a temperature gradient. The crystal structure of Cr3Ti4(PO4)6 has been refined from single crystal data (P1 (No.2), Z=1; a=9.4139(13)Å, b=8.1056(9)Å, c=6.3517(8)Å, α=101.25(1)°, β= 107.54(1)°, γ=106.23(1)° (from Guinier-photographs); conventional residual R1=0.0312 for 2810 F0 > 4σ(F0), 170 parameters; 19 atoms in the asymmetric unit). A preliminary refinement shows CrTi2(P2O7)2-black (P63/m (No.176), Z=3, a=8.9855Å, c=12.3183Å, R1=0.0884 for 1013 F0 > 4σ(F0), 51 parameters; 11 atoms in the asymmetric unit) to be structurally related to FeIIFe2III(P2O7)2. The Guinier diffraction pattern of CrTi2(P2O7)2-purple shows strong similarity to that of CuFe2(P2O7)2.
Absorption bands in the electronic spectra of Cr3Ti4(PO4)6, CrTi2(P2O7)2-black, and CrTi2(P2O7)2-purple are in agreement with electrons located on Cr2+ and Ti3+ ions.
