Sr(Ag_1−xLi_x)₂Se₂ and [Sr₃Se₂][(Ag_1−xLi_x)₂Se₂] Tunable Direct Band Gap Semiconductors

Abstract

Synthesizing solids in molten fluxes enables the rapid diffusion of soluble species at temperatures lower than in solid‐state reactions, leading to crystal formation of kinetically stable compounds. In this study, we demonstrate the effectiveness of mixed hydroxide and halide fluxes in synthesizing complex Sr/Ag/Se in mixed LiOH/LiCl. We have accessed a series of two‐dimensional Sr(Ag1−xLix)2Se2 layered phases. With increased LiOH/LiCl ratio or reaction temperature, Li partially substituted Ag to form solid solutions of Sr(Ag1−xLix)2Se2 with x up to 0.45. In addition, a new type of intergrowth compound [Sr3Se2][(Ag1−xLix)2Se2] was synthesized upon further reaction of Sr(Ag1−xLix)2Se2 with SrSe. Both Sr(Ag1−xLix)2Se2 and [Sr3Se2][(Ag1−xLix)2Se2] exhibit a direct band gap, which increases with increasing Li substitution (x). Therefore, the band gap of Sr(Ag1−xLix)2Se2 can be precisely tuned via fine‐tuning x that is controlled by only the flux ratio and temperature.

Syntheses of a series of BaCu2−xAgxSe2 (x = 0 – 1.0) selenides and evaluation of their thermoelectric properties

“…Examples of such compounds are the BaCu 2 Se 2 , 21 CuAgSe, 22 and AgInSe 2 . 23 Many groups have investigated the structural aspects of the AkM 2 Q 2 (Ak = Sr/Ba; M = Cu/Ag; Q = chalcogen = S, Se, and Te), [24][25][26][27][28][29] along with their transport properties. One of the interesting members of this family is BaCu 2 Se 2 , which crystallizes in two polymorphs: the a-form with an orthorhombic structure and the tetragonal b-form.…”