From BPS4 to AB3P2S10 (A = Na, K): cations inducing dimension reduction and bandgap enlargement

Regulating the crystal structure by cations is one of the most effective methods to adjust the performances of optical materials and enrich the structural chemistry of solid-state inorganic crystals. In this work, only boron-thiophosphate BPS4 (BPS) was used as the template. By introducing alkali metal ions, Na+ and K+, the synthesis, structural revolution, and bandgap adjustment were studied. Namely, the first quaternary boron-thiophosphates, AB(3)P(2)S(10) (A = Na, K) (ABPS) were obtained, whose anion skeleton decreased to zero dimension from one dimension (1D) in BPS. In addition, the bandgap showed obvious improvement from 3.30 (BPS) to 3.42 and 3.49 eV (ABPS). Structural studies and theoretical analyses indicated that the insert of cations separates the infinite chains to [B3P2S10] clusters, localizes the electrons around the S2- in [BS4] and [PS4] groups, and widens the bandgaps. This work could enrich the structural chemistry of boron-thiophosphates and reveal that ionic bonds can modulate the covalent skeleton and show the effect on the optical properties.

Automated summary

Regulating the performances of optical materials and enriching the structural chemistry of solid-state inorganic crystals can be achieved by controlling the crystal structure using cations. In this work, the synthesis, structural revolution, and bandgap adjustment of boron-thiophosphate BPS4 (BPS) were studied by introducing Na+ and K+ ions. The obtained quaternary boron-thiophosphates, AB(3)P(2)S(10) (A = Na, K) (ABPS), showed a decreased anion skeleton dimension and improved bandgap compared to BPS. Structural studies and theoretical analyses revealed that the introduction of cations separated the infinite chains, localized the electrons, and widened the bandgaps. This work enriches the structural chemistry of boron-thiophosphates and demonstrates the effect of ionic bonds on the optical properties.