The unstable thermoelectric effect in non-stoichiometric Cu2Se during the non-equilibrium phase transition

Abstract

The superionic α ↔ β phase transition in Cu1.96Se thermoelectric material is investigated by means of thermal analysis (DSC) and measurements of Seebeck coefficient and electrical conductivity. Results of the DSC measurements with 1–10 K/min heating and cooling rates show that the material is close to the equilibrium phase composition during the transformation. However, the kinetic limitation of the process exists, which is indicated by supercooling. At the beginning of the β → α transition, the most significant kinetic delay was attributed to the nucleation of the α phase. During the phase transformation, the Seebeck coefficient was lower than in a stabilised material (measured with 0.1 K/min heating/cooling rate). During cooling, a decrease from 130 μV/K (in a stabilised measurement) to 7 μV/K (5 K/min cooling rate) was observed. The deviation from the expected values of the Seebeck coefficient was correlated with the difference between the actual and equilibrium phase compositions. Graphical abstract

Compressibility Studies of Copper Selenides Obtained by Cation Exchange Reaction Revealing the New CsCl Phase

“…The extent of the CER as well as the resulting structures depends , on the chemical nature of the guest cation, their ionic radii and oxidation states, and the choice of ligands and solvation environments . CERs in CdSe NCs , with zinc-blende and wurtzite structures were used to synthesize zinc-blende Cu 2– x Se NCs that can reveal superionic properties meaning desirable thermoelectric properties quantified by a high Seebeck coefficient − and low thermal conductivity as well as other interesting optoelectronic properties. Copper selenides can exist in a variety of compositions, each with their unique crystal structure, optoelectronic signals, plasmonic resonance features, ,, and other emergent properties. , …”

Compressibility Studies of Copper Selenides Obtained by Cation Exchange Reaction Revealing the New CsCl Phase

“…The extent of the CER as well as the resulting structures depend 31,32 on the chemical nature of the guest cation, their ionic radii and oxidation states and the choice of ligands and solvation environments 33 . CERs in CdSe NCs 20,21 with zinc blende and wurtzite structures were used to synthesize zinc blende Cu2-xSe NCs that can reveal superionic properties meaning desirable thermoelectric properties quantified by high Seebeck coefficient [28][29][30][31] and low thermal conductivity 32 as well as other interesting optoelectronic 21 properties. Copper selenides can exist in a variety of compositions, each with their unique crystal structure 33 , optoelectronic signals 34 , plasmonic resonance features 21,35,36 and other emergent properties 37,38 .…”