Infrared spectroscopy and the structure of rare-earth chromium borates RCr3(BO3)4 (R = La-Er)

Structural, Electronic and Vibrational Properties of YAl3(BO3)4

“…The typical Infrared spectra of huntite-like ReM 3 (BO 3 ) 4 (Re = Y, rare-earth element, M = Al, Ga, Fe, Cr) compounds with noncentrosymmetric trigonal structure (R32 space group) should contain an empty gap in the range 1050-1200 cm −1 [62][63][64]. However, as discussed earlier [65][66][67], the borates with large rare-earth elements can form not only trigonal but also monoclinic structures depending on the growth conditions. Some extra bands (in comparison with trigonal structure) were observed in the range of 1050-1200 cm −1 and these bands assigned to ν 3 vibrations of BO 3 3− ions [67,68].…”

Crystallochemical Design of Huntite-Family Compounds

“…In the overwhelming number of cases, the crystal structures (first of all, coordinates of atoms) of the samples were refined by the full-profile Rietveld method on polycrystalline samples obtained by the solid-state reaction (LnFe 3 (BO 3 ) 4 with the Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, (Y), Ho; LnGa 3 (BO 3 ) 4 with the Ln = Sm, Gd, Y, Ho, Er) [34,53] or on single crystals synthesized by the flux method and ground to a powder (LnAl 3 (BO 3 ) 4 with the Ln = Nd, Sm, Eu, Gd, Tb, Dy, (Y), Ho, Er, Yb; LnFe 3 (BO 3 ) 4 with the Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, (Y), Ho; LnGa 3 (BO 3 ) 4 with the Ln = Gd) [1,54,56,59,61,66,68]. Assignment of a series of rare-earth orthoborates (LnAl 3 (BO 3 ) 4 with the Ln = Nd, Eu, Gd, Tb, Dy, (Y), Ho, Er, Tm, Yb; LnFe 3 (BO 3 ) 4 with the Ln = Eu, Gd, Y; LnCr 3 (BO 3 ) 4 with the Ln = Sm, Eu, Gd, Tb, Dy; LnGa 3 (BO 3 ) 4 with the Ln = Nd, Eu, Gd, (Y), Ho) to the space group R32 is performed on powdered single crystals obtained by the flux method using IR spectroscopy coupled with the group-theoretical analysis [26,42,45,51,70,71,73], temperature-dependent high-resolution optical absorption Fourier spectroscopy and Raman spectroscopy (LnFe 3 (BO 3 ) 4 with the Ln = Pr, Nd) [57,58,60].…”

“…IR/S, T s = 143 K [65] R32: D/P [1], D/? [27], IR/S (50:50, 900-950 • C; 70:30, 1040-1050 • C) [70], IR/S (1:1; 1.5:1; 2.3:1) [71], IR/S [26,45] R32: D/? [27], D/P [34,54], IR/P [45] R32: ?…”

“…The space group C2/c is known for the LnAl 3 (BO 3 ) 4 with the Ln = Pr, Nd, Sm, Eu, Tb, Ho (the structure is refined, for example, in [97]); LnFe 3 (BO 3 ) 4 with the Ln = Nd; LnCr 3 (BO 3 ) 4 with the Ln = La, Pr, Nd, Sm, Tb, Dy, Ho; LnSc 3 (BO 3 ) 4 with the Ln = La, Ce, Pr ( Table 1). The centrosymmetry was determined by spectroscopic studies using a factor-group analysis of vibrations (for the LnAl 3 (BO 3 ) 4 with the Ln = Pr [42], Nd [42,45]; LnFe 3 (BO 3 ) 4 with the Ln = Nd [45]; LnCr 3 (BO 3 ) 4 with the Ln = La (Figure 10), Pr, Tb, Dy, Ho [70,71], Nd [26,45,70,71], Sm [70,72]). The LnSc 3 (BO 3 ) 4 crystals with the Ln = La, Ce, obtained by the Czochralski method, crystallize in the centrosymmetric space group C2/c), according to a study of their nonlinear optical properties [35].…”

Structural and optical properties of NdxGd1−xCr3(BO3)4solid solutions

“…The analysis of thermal, magnetic, and optical properties of NdCr3(BO3)4 has shown that the compound orders antiferromagnetically into an easy-plane magnetic structure at the temperature TN=8 K [1]. The RE chromium borates have polytypic nature and, depending on growth conditions, crystallize in two modifications, namely, a non-centrosymmetric rhombohedral one with the space group R32 and a centrosymmetric monoclinic one with the space group C2/с [4,5]. Coexistence of differently ordered fragments in a single crystal is a characteristic feature of these compounds.…”