Developing Intense Blue and Magenta Colors in α‐LiZnBO₃: The Role of 3d‐Metal Substitution and Coordination

Abstract

We describe the synthesis, crystal structures, and optical absorption spectra/colors of 3d-transition-metal-substituted α-LiZnBO derivatives: α-LiZn M BO (M =Co (0<x<0.50), Ni (0<x≤0.05), Cu (0<x≤0.10)) and α-Li Zn M BO (M =Mn (0<x≤0.10), Fe (0<x≤0.25)). The crystal structure of the host α-LiZnBO , which is both disordered and distorted with respect to Li and Zn occupancies and coordination geometries, is largely retained in the derivatives, which gives rise to unique colors (blue for Co , magenta for Ni , violet for Cu ) that could be of significance for the development of new, inexpensive, and environmentally friendly pigment materials, particularly in the case of the blue pigments. Accordingly, this work identifies distorted tetrahedral MO (M=Co, Ni, Cu) structural units, with a long M-O bond that results in trigonal bipyramidal geometry, as new chromophores for blue, magenta, and violet colors in a α-LiZnBO host. From the L*a*b* color coordinates, we found that Co-substituted compounds have an intense blue color that is stronger than that of CoAl O and YIn Mn O . The near-infrared (NIR) reflectance spectral studies indicate that these compounds exhibit a moderate IR reflectivity that could be significant for applications as "cool pigments".

Color Tuning in Garnet Oxides: The Role of Tetrahedral Coordination Geometry for 3 d Metal Ions and Ligand–Metal Charge Transfer (Band‐Gap Manipulation)

“…4 T 1 (G)/ 4 T 2 (G) transitions within the tetrahedral symmetry,s imilart ot he assignmentsf or Fe 3 + :LiAlO 2 , [32] Fe 3 + :SiO 2 , [33] and Fe 3 + in LiZnBO 3 . [9] Ca 3 Sb 2 Fe 2 Zn 1À Àx M II [8,[21][22][23] for tetrahedral Co 2 + ,s imilar to that observed for the Ca 3 Sb 2 Ga 2 Zn 1Àx Co x O 12 (0 < x 1.0) members. Interestingly,w e observe an enormous redshift in the E g edge as the value of x increases in Ca 3 Sb 2 Fe 2 Zn 1Àx Co x O 12 (0 < x 1.0).…”

“…[8,26] It may be noted that stabilizing Ni 2 + in the tetrahedral coordination is not common. On the other hand, cobalt (Co 2 + )i n tetrahedral coordination is known (e.g.,s pinel CoAl 2 O 4 , [27] willemite Co x Zn 2Àx SiO 4 , [28] and a-LiZn 0.5 Co 0.5 BO 3 [9] ). All the compoundse xhibit intense blue color.N ickel (Ni 2 + )i nt etrahedral coordination is limited to af ew examples:N i-doped a-LiZnBO 3 , [9] Ni-doped gahnite, [25] and Ni-doped hibonite (CaAl 12 O 19 ).…”

“…On the other hand, cobalt (Co 2 + )i n tetrahedral coordination is known (e.g.,s pinel CoAl 2 O 4 , [27] willemite Co x Zn 2Àx SiO 4 , [28] and a-LiZn 0.5 Co 0.5 BO 3 [9] ). All the compoundse xhibit intense blue color.N ickel (Ni 2 + )i nt etrahedral coordination is limited to af ew examples:N i-doped a-LiZnBO 3 , [9] Ni-doped gahnite, [25] and Ni-doped hibonite (CaAl 12 O 19 ). [26] These compounds exhibit magenta, blue, and turquoise colors,r espectively.I nt he presents tudy,t he garnet host stabilizes Ni 2 + in the tetrahedral site with as ky blue color, which is unique and significant.…”

“…In the recent past, we explored distorted coordination geometries of the transition elements in many hosts and produced uniquelyc olored solids. [9][10][11] Many minerals have been known to form with bright colors, [1] and this is due to doping of transition elements of varying concentrations.O ft he many minerals, Garnet is important, forms in ac ubic symmetry (space group: Ia3 d), and has the general formula [A 3 ][B 2 ][C 3 ]O 12 ,i nw hich the A, B, andC cations are 8-(dodecahedron), 6-(octahedron), and 4-(tetrahedron) coordinate, respectively.W ell-known garnets include Y 3 Al 5 O 12 (YAG), Y 3 In 5 O 12 (YIG), and Y 3 Ga 5 O 12 (YGG), and they have been investigated as laser hosts over the years. [12] The coordination variability of the cations in the garnets tructure has been gainfully exploited by producing many interesting compounds.…”

Exploring the Corundum Structure as a Host for Colored Compounds – Synthesis, Structures, and Optical Studies of (MM′)3TeO6 (M = Mg, Mn, Co, Ni, Zn; M′ = Mg, Mn, Co, Ni, Cu)

“…Of the many studies, the observations of the blue color in Mn 3+ ‐substituted YInO 3 and Co 2+ ‐substituted ZnMoO 4 as well as the different colors in copper‐substituted apatites and transition‐metal‐substituted MgTi 2 O 5 have shown much promise. Recently, we explored the distorted coordination geometries of transition elements in different hosts, which resulted in uniquely colored compounds . Continuing our efforts in this direction, we have now investigated the corundum‐related structure of the general formula (MM′) 3 TeO 6 (M = Mg, Mn, Co, Ni, Zn; M′ = Mg, Mn, Co, Ni, Cu).…”