Experiment and First-Principles Calculations of A₂Mg₂TeB₂O₁₀ (A = Pb, Ba): Influences of the Cosubstitution on the Structure Transformation and Optical Properties

Abstract

Two new A2Mg2TeB2O10 (A = Pb, Ba) compounds have been synthesized by the high temperature solution method. A2Mg2­TeB2O10 (A = Pb, Ba) crystallize in the same space group Cmca and feature a 3D [B2Te­Mg2O10]4– framework structure. A2Mg2­TeB2O10 (A = Pb, Ba) can be regarded as the cosubstitution of Na2RE2­TeB2­O10 (RE = Y, Dy–Lu), which crystallize in a different space group, P21/c. The discussion on the structure transformation from A2Mg2­TeB2­O10 (A = Pb, Ba) to Na2RE2­TeB2O10 (RE = Y, Dy–Lu) indicates that the cosubstitution of two cations with different valence states can change the dimension of cation groups in the crystal structure, which can further alter the arrangements of the anion groups. Furthermore, the band gap and birefringence have been changed after the cosubstitution. The influences of the cosubstitution on the band gap and birefringence have been discussed through first-principles calculations and structure comparison. In addition, the IR spectra and TG-DSC curves of title compounds were studied.

Centrosymmetric Rb[Te2O4(OH)5] and noncentrosymmetric K2[Te3O8(OH)4]: metal tellurates with corner and edge-sharing (Te4O18)12− anion groups

“…The observed interference colours are respectively two-order pink and two-order blue for RTOH and KTOH , which the corresponding retardation values are 1100 nm and 550 nm based on the Michal–Levy chart, and measured the crystal thicknesses are about 21.9 μm and 12.3 μm. As a consequence, the measured birefringence can be 0.050 and 0.045, respectively, comparable with that of other tellurate compounds such as Li 2 ZrTeO 6 (Δ n cal = 0.0638 at 1064 nm), 19 Ba 2 Mg 2 TeB 2 O 10 (Δ n cal = 0.046 at 1064 nm), 49 and larger than PbTeGeO 6 (Δ n cal = 0.032 at 1064 nm) 17 and Na 2 Y 2 TeB 2 O 10 (Δ n cal = 0.021 at 1064 nm), 49 indicating their potential application combined with the NLO phase-matching behaviour. The above method of measuring birefringence only is the in-plane value of the measured crystals, suggesting RTOH and KTOH single crystals may have the potential of larger birefringence values.…”

“…The characteristic peaks around 3200 cm −1 are denoted as the asymmetric and symmetric stretching of –OH units; the peaks at 1250 cm −1 and 1000 cm −1 are assigned to be the Te–O–H bending modes of vibration; the peaks in the region from 740 cm −1 to 415 cm −1 are regarded as the Te–O asymmetric, symmetric, and bending vibrations of TeO 6 6− octahedra, which the descriptions are consistent with those reported in the literature. 26,49 In the Raman spectra (Fig. S8†), the peaks from 800 cm −1 and 540 cm −1 are assigned to the stretching mode of the octahedral Te–O group, and the peaks below 500 cm −1 are attributable to bending modes of the Te–O group, corresponding to the infrared spectra.…”

Hg2(SeO3)(SO4): the first sulfate selenite with large birefringence explored from d10transition metal compounds

“…It has been reported that cations with stereochemically active lone-pair electrons, such as Sn 2+ , Pb 2+ , Se 4+ and Te 4+ , can play positive roles in the birefringence properties due to their strong anisotropy. 9–15 For example, an excellent birefringent crystal, α-SnF 2 , which exhibits a large birefringence (0.177 at 546 nm), a short UV cut-off edge and easy crystal growth at ambient temperature, was reported in 2020 by Pan's group. 16 Recently, our group reported a series of inorganic oxides with large birefringence and wide band gaps via the combination of tellurite groups and sulfate tetrahedra, 17 i.e.…”

CsY(SO4)2·4H2O: A Deep-Ultraviolet Birefringent Crystal Induced by an Edge-Sharing Connection

“…In addition, the birefringence of 1 is even comparable to those of borates containing π-conjugated anionic groups, such as Ba 2 Mg 2 TeB 2 O 10 (0.046@1064 nm) and Na 2 Y 2 TeB 2 O 10 (0.021@1064 nm) . The large birefringence of 1 may originate from the unique layered structure induced by the edge-sharing connection mode between SO 4 and YO 8 groups.…”