Systematic color variation across the solid solution members, Li2Mn1-xTixO3 (0.0 ≤ x ≤ 1.0)

Abstract This study investigated the formation of a layered rock salt superstructure series for the oxides Li 2 (Mn 1- x Ti x )O 3 (0.0 ≤  x  ≤ 1.0) and the effects of the progressive substitution of Ti 4+ ( d 0 ) for Mn 4+ ( d 3 ) on the structural and optical properties. The members where 0.0  x  ≤ 0.85 adopted the structure of Li 2 MnO 3 (S.G. C2/m ; a  = 4.934 (1); b  = 8.530 (2); c  = 5.021 (1) A; β  = 109.46 (1)°) according to powder X-ray diffraction measurements and the characteristic Raman bands. By contrast, the members corresponding to the range of 0.85  x 2 TiO 3 (S.G. C2/c ; a  = 5.0585 (2); b  = 8.7780 (4); c  = 9.7452 (4) A; β  = 100.183 (3)°). Starting from the brick-red color of Li 2 MnO 3 , the color changed to ochre and then to orange as the concentration of Ti 4+ increased, and finally to colorless for Li 2 TiO 3 . The corresponding photoluminescence spectrum for the lowest (0.05) Mn 4+ substitution in Li 2 TiO 3 confirmed the presence of Mn 4+ ions, where the bands at 684 and 698 nm were due to the transitions: 2 E → 4 A 2 and 2 T 1 → 4 A 2 . The photoluminescence intensities decreased systematically as the Mn 4+ content increased starting from x  = 0.95. The ionic conductivity measurements indicated the temperature dependence of the nominal conductivity values.