Birefringence Disparity Induced by Synergistic Effects of Stereochemically Active Lone Pairs

Abstract

Birefringent crystals with significant optical anisotropy have played a pivotal role in laser technology and scientific research by modulating and controlling light polarization. In this study, we have successfully synthesized three new birefringent materials with mixed-valence antimony, namely, KSb 3 O 6 , RbSb 3 O 6 , and α-Sb 2 O 4 , through the introduction of Sb 3+ with stereochemically active lone pairs (SCALP) to the total oxygen system using a high-temperature solution method. To the best of our knowledge, K/RbSb 3 O 6 represents the first alkali metal mixedvalence Sb-based oxide. Interestingly, despite their similar sandwich structure, these materials exhibit vastly different levels of birefringence (almost 10 times difference). It is worth noting that α-Sb 2 O 4 demonstrates the largest experimental birefringence (0.201 at 546 nm) among non-π-conjugated Sb-based oxides to date, which can be attributed to the synergistic effect of SCALP group distortion and arrangement. These findings hold valuable implications for guiding future efforts in designing and synthesizing large birefringent materials.

Synergistic engineering of ultraviolet metal-free crystals with exceptional birefringence via pyridine-derived dimers

“…The discrepancy between the calculated and experimental bandgaps (4.12 eV for compound 1 and 4.00 eV for compound 2 ) can be attributed to the discontinuity in the exchange-correlation energy functional when using the GGA-PBE approximation. 46–49 A scissor correction was applied in subsequent analyses.…”

β-LaTeBO5 and RETeBO5 (RE = Y, Gd, Tb): explorations of new optical materials in the RE(iii)–Te(iv)–B–O system

“…4,12,15 In addition, the [TeO 3 ] 2− group is a member of another important class of functional groups, which possess sterically active lone-pair electrons, that have susceptibility to second-order Jahn–Teller distortion and substantial microscopic polarizabilities. 16,17 Compared to other non-π-conjugated systems, such as the [PO 4 ] 3− and [SeO 3 ] 2− groups, the [TeO 3 ] 2− group demonstrates significantly greater anisotropy of polarizability, lower phonon energy, and a broader infrared transmission range. 18,19 In 2024, our research group reported Hg 4 (Te 2 O 5 )(SO 4 ), which features novel [Hg 4 (Te 2 O 5 )] ∞ layers and [Te 2 O 5 ] 2− dimers, as well as a large birefringence of 0.542@546 nm.…”