High temperature crystal structure and DSC of Sn2P2S6

Scott, Brian L.; Pressprich, M. R.; Willet, R.D.; Cleary, David

doi:10.1016/s0022-4596(05)80262-2

Cited by 86 publications

(83 citation statements)

References 14 publications

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“…[3] They can exhibit fundamentally and technologically important nonlinear optical [4] and ferroelectric properties, [5] reversible redox chemistry relevant to secondary batteries, [6] photoluminescence, [7] and phasechange properties.[8] However, no metallic selenophosphates have been reported to date. This lack is in striking contrast to the oxophosphate counterparts, which are a well-defined series of unusual metals, such as (PO 2 ) 4 (WO 3 ) 2m , A x (PO 2 ) 4 -(WO 3 ) 2m (A = Na, K), and A x (P 2 O 4 ) 2 (WO 3 ) 2m (A = K, Rb, Tl, Ba).…”

mentioning

confidence: 99%

Rb₄Sn₅P₄Se₂₀: A Semimetallic Selenophosphate

Chung¹,

Biswas²,

Song³

et al. 2011

Angew Chem Int Ed

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Chalcophosphates are ternary (A/P/Q) and quaternary (A/M/ P/Q) compounds with [P y Q z ] nÀ anions in their structure, where M is a metal, A is an alkali metal, and Q is sulfur, [1] selenium, [2] or tellurium. [3] They can exhibit fundamentally and technologically important nonlinear optical [4] and ferroelectric properties, [5] reversible redox chemistry relevant to secondary batteries, [6] photoluminescence, [7] and phasechange properties.[8] However, no metallic selenophosphates have been reported to date. This lack is in striking contrast to the oxophosphate counterparts, which are a well-defined series of unusual metals, such as (PO 2 ) 4 (WO 3 ) 2m , A x (PO 2 ) 4 -(WO 3 ) 2m (A = Na, K), and A x (P 2 O 4 ) 2 (WO 3 ) 2m (A = K, Rb, Tl, Ba).[9] The metallic properties of these phosphates derive from mixed valency of the transition metals. There have been attempts to explore chalcophosphate compounds as thermoelectric materials. For example, in light of the known alkali chalcophosphate compounds, the Tl + analogues Tl 3 Ti 2 P 5 S 18 , Tl 2 CeP 2 S 7 , TlTiPS 5 , and Tl 2 BiP 2 S 7 were investigated.[10] However, they were wide-gap semiconductors and too resistive for such applications. Inclusion of a transition metal gave a better-conducting semiconductor Ni 3 Cr 2 P 2 Q 9 (Q = S, Se).[11]Herein, we report on Rb 4 Sn 5 P 4 Se 20 , the first metallic selenophosphate. Its structure belongs to a class not previously known for this family, namely, a lamellar hybrid of "conducting" with the metallic characteristics. The results of ab initio density functional theory (DFT) calculations using the allelectron full-potential linearized augmented plane wave (FLAPW) method [12] reveal that the metallic behavior originates from the overlap of conduction and valence bands and not any formal mixed valency.Rb 4 Sn 5 P 4 Se 20 was synthesized by the reaction of Sn/Rb 2 Se/ P 2 Se 5 /Se in a 1:1:1:5 molar ratio at 490 8C for four days. However, the complicated Lewis acid-base equilibria in the flux also yielded Rb 3 Sn(PSe 5 )(P 2 Se 6 ) [13] as by-product. On the other hand, the direct combination of the elements and reaction at 515 8C gave SnP 2 Se 6 . [14] We could obtain pure Rb 4 Sn 5 P 4 Se 20 only by direct combination reactions of Sn/ Rb 2 Se/P/Se at 850 8C. According to differential thermal analysis (DTA), Rb 4 Sn 5 P 4 Se 20 melts congruently at 517 8C, and the melt crystallizes at 494 8C. The X-ray powder diffraction patterns before and after melting and recrystallization were identical (Supporting Information Figure S1).Rb 4 Sn 5 P 4 Se 20 crystallizes in the trigonal space group P3 m1.[15] The structure features thick anionic [Sn 5 P 4 Se 20 ] n 4nÀ layers ( Figure 1 and Figure S2 in the Supporting Information). The layer is based on the SnSe 2 structure (CdI 2 type); the latter consists of planes of hexagonally packed Se atoms interleaved with planes of octahedral Sn atoms.[16] The removal of 1

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mentioning

confidence: 99%

Rb₄Sn₅P₄Se₂₀: A Semimetallic Selenophosphate

Chung¹,

Biswas²,

Song³

et al. 2011

Angew Chem Int Ed

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“…These data confirm the speculation about the possible existence of a two-well potential for Sn atoms in the paraelectric phase of the crystals studied. The X-ray structural studies also confirm a substantial increase of the mean-square shifts for Sn atoms at the transition into paraelectric phase, both in Sn 2 P 2 S 6 [16] and Sn 2 P 2 Se 6 [17,18] (figure 8). Figure 8.…”

Section: Introductionmentioning

confidence: 63%

THE PHASE TRANSITIONS CHARACTER AND MICROSCOPIC MODELS FOR Sn_2P_2S(Se)_6 FERROELECTRICS

Vysochanskii¹,

Drobnich²

2002

Condens. Matter Phys.

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The paper considers an example of concrete objects, i.e. ferroelectrics of Sn 2 P 2 S 6 family, for which, according to general estimations, a correlation between the shape of a phase diagram (the presence of a Lifshitz point and of a tricritical point) and a crossover "displacive to order/disorder" is observed. Simulations by means of microscopic models, which most adequately represent a dipole ordering in these crystals, are analyzed. A dimension dependence of a ferroelectric phase transition temperature for microcrystals of Sn 2 P 2 S 6 compound is considered.

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“…They have the form of parallelopipeds with dimensions of about 5x5x5 mm. Since the crystals studied belong to the monoclinic lattice system, we used the socalled pseudorhombohedral setting with monoclinic angle close to 90°(for example, β ≈ 91 15°for Sn 2 P 2 S 6 crystals at T = 383 K) [6]. Measurements were carried out in right angle, backscattering and 90A scattering geometries.…”

Section: Experimental Details and Resultsmentioning

confidence: 99%

“…There are a variety of interesting physical phenomena including structural phase transitions in these materials [1]. Since the acoustic properties of Sn 2 P 2 (Se S 1− ) 6 ferroelectric crystals were studied earlier [1][2][3][4][5] …”

Section: Introductionmentioning

confidence: 99%