Electronically Driven Structural Distortions in Lithium Intercalates of then= 2 Ruddlesden−Popper-Type Host Y₂Ti₂O₅S₂:  Synthesis, Structure, and Properties of Li_xY₂Ti₂O₅S₂(0 <x< 2)

Abstract

Lithium intercalation into the oxide slabs of the cation-deficient n = 2 Ruddlesden-Popper oxysulfide Y(2)Ti(2)O(5)S(2) to produce Li(x)Y(2)Ti(2)O(5)S(2) (0 < x < 2) is described. Neutron powder diffraction measurements reveal that at low levels of lithium intercalation into Y(2)Ti(2)O(5)S(2), the tetragonal symmetry of the host is retained: Li(0.30(5))Y(2)Ti(2)O(5)S(2), I4/mmm, a = 3.80002(2) A, c = 22.6396(2) A, Z = 2. The lithium ion occupies a site coordinated by four oxide ions in an approximately square planar geometry in the perovskite-like oxide slabs of the structure. At higher levels of lithium intercalation, the symmetry of the cell is lowered to orthorhombic: Li(0.99(5))Y(2)Ti(2)O(5)S(2), Immm, a = 3.82697(3) A, b = 3.91378(3) A, c = 22.2718(2) A, Z = 2, with ordering of Li(+) ions over two inequivalent sites. At still higher levels of lithium intercalation, tetragonal symmetry is regained: Li(1.52(5))Y(2)Ti(2)O(5)S(2), I4/mmm, a = 3.91443(4) A, c = 22.0669(3) A, Z = 2. A phase gap exists close to the transition from the tetragonal to orthorhombic structures (0.6 < x < 0.8). The changes in symmetry of the system with electron count may be considered analogous to a cooperative electronically driven Jahn-Teller type distortion. Magnetic susceptibility and resistivity measurements are consistent with metallic properties for x > 1, and the two-phase region is identified as coincident with an insulator to metal transition.

Room temperature oxidative intercalation with chalcogen hydrides: Two-step method for the formation of alkali-metal chalcogenide arrays within layered perovskites

“…Many such oxychalcogenides are already known including those that exhibit interesting magnetic and electronic properties [31][32][33][34][35][36][37][38][39][40][41][42]. The series Sr 2 MnO 2 Cu 2mÀd S m+1 (m = 1, 2, and 3), for example, contains copper-sulfide layers of varying thicknesses (m) and is found to exhibit metamagnetic behavior [32].…”

“…A 2 F 2 Fe 2 OCh 2 (A = Sr, Ba; Ch = S, Se) compounds, for instance, display a frustrated antiferromagnetic checkerboard lattice [42]. Other alkali-metal containing oxysulfides have been prepared topochemically; Y 2 Ti 2 O 5 S 2 for example has been reductively intercalated with Li, Na and K [34][35][36][37]. The interlayer coordination geometry for K in KY 2 Ti 2 O 5 S 2 is similar to that seen for Rb in Rb-S (Fig.…”

Y2Ti2O5S2 as a high performance anode material for Li ion batteries

“…While Li + occupies 4 coordinated square sites, Na + is suggested to occupy 12 coordinated sites [5][6][7]. In Li + -intercalated YTOS, Li x Y 2 Ti 2 O 5 S 2 , Li + was accommodated up to at least x = 1.85 [7]. The crystal structure evolves from tetragonal to orthorhombic to tetragonal upon Li doping.…”

“…1a, the crystal structure of YTOS consists of an alternating stacking of Ti 2 O 5 double layer units with corner shared TiO 5 pyramids and Y 2 S 2 layer units [4]. The crystal chemistry and electronic structure of YTOS intercalated with Li + and Na + have been previously studied [5][6][7]. Both Li + ions and Na + ions are located within Ti 2 O 5 layer units.…”

3D Transition Metal Ordering and Rietveld Stacking Fault Quantification in the New Oxychalcogenides La2O2Cu2–4xCd2xSe2

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] These properties are, of course, intimately related to their 3D structure and influenced by the specific architectures enforced or enabled by the simultaneous bonding requirements of different cation/anion combinations. We have previously described how combining rigid-geometry oxide building blocks with more flexible or adaptive chalcogenide layers can lead to infinitely adaptive structures with remarkable structural complexity (though governed by simple rules) in two dimensions.…”