The Family of Ln2Ti2S2O5 Compounds (Ln=Nd, Sm, Gd, Tb, Dy, Ho, Er, and Y): Optical Properties

Fast lithium-ion conductivity in the ‘empty-perovskite’ n = 2 Ruddlesden–Popper-type oxysulphide Y2Ti2S2O5

“…Both hybrid functionals overestimate the experimentally-reported bandgap of 1.9 eV-2.0 eV. 33,52 PBE nds a bandgap of 1.08 eV, underestimated with respect to experiment. The bandgap calculated with HSE06 is 2.16 eV, close to the value reported from experiment.…”

“…Materials with Wadsley-Roth-type structures typically display an insulator-to-metal transition at low levels of lithiation, due to delocalised electrons in the conduction band, which is composed of relatively diffuse Nb 4d orbitals. 18,29,30,53,70 Y 2 Ti 2 S 2 O 5 is a medium-gap semiconductor 33 with a bandgap of $2 eV, and it has been applied as a photocatalyst for overall water-splitting under visible light. 52 Upon intercalation of Li + ions, Li x Y 2 Ti 2 S 2 O 5 is reported to behave as a semiconductor at x ¼ 0.3, with some degree of Curie contribution to the magnetic susceptibility, indicating the presence of localised S ¼ 1/2 magnetic moments, attributed to localised electrons on Ti 3+ ions.…”

“…1e). [31][32][33] In a conventional R-P phase, with stoichiometry A n+1 B n O 3n+1 (for n $ 2), the corner-sharing framework of octahedra in the 'perovskite' layers would be occupied by 12-coordinate A-site cations. In Y 2 Ti 2 S 2 O 5 , these units are empty, leaving a 2D plane of 'ReO 3 -like' type I Wadsley-Roth cavities into which Li + , Na + and Mg 2+ ions can be intercalated.…”

Crystal structures of two new oxysulfides La5Ti2MS5O7 (M=Cu, Ag): evidence of anionic segregation

“…This is in good agreement with the oxidation state equilibrium reached for La 5 Ti 2 MS 5 O 7 (M=Cu, Ag) by considering La(+III), M(+I) and Ti(+IV) counterbalancing S(ÀII) and O(ÀII). 14 eV with Ln from Nd to Er) [12]. It is worth noting that the Cu compound has a smaller gap than the Ag one, which is the opposite than the one observed for the pristine sulfides Cu 2 S and Ag 2 S 1.10 and 0.92 eV, respectively [13].…”

Opto‐electronic properties and light‐emitting device application of widegap layered oxychalcogenides: LaCuOCh (Ch = chalcogen) and La2CdO2Se2

“…For instance, ultraviolet (UV)-blue photoluminescence (PL) originating from room temperature excitons [43,26,27], which has not been observed for other widegap p-type materials or three-dimensional materials associated with the constituent layers such as Cu 2 Ch reported so far. Thus, this material series can be a promising candidate for an active layer of light-emitting diodes (LEDs) that operate in the UV-blue region as well as transparent p-type conductors, and therefore many oxychalcogenides are extensively studied in various fields such as novel material syntheses [44][45][46][47][48][49][50][51][52][53][54][55], opto-electronic properties [56][57][58][59][60][61][62][63][64][65][66][67], and magnetic properties [68][69][70][71].…”