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1.
Inorg Chem ; 62(31): 12600-12610, 2023 Aug 07.
Article in English | MEDLINE | ID: mdl-37478003

ABSTRACT

Coinage metal chalcogenides offer ideal prerequisites for high thermoelectric performance and sensor applications, with their usually low lattice thermal and high electrical conductivity, as well as small band gaps. In the solid solution Cu1.5SeyTe1-y we synthesized phase pure materials with y = 0.2-0.7 and characterized them concerning selected physical properties. X-ray crystal structure determination was performed for two representatives of the solid solution, Cu1.5Se0.3Te0.7 and Cu1.5Se0.5Te0.5. The entire series crystallizes cubically, in space group Pm3̅n. No structural changes are observed between room temperature and the synthesis temperature of 723 K. The conductivity measurements and Seebeck coefficients of Cu1.5Se0.3Te0.7 and Cu1.5Se0.5Te0.5 indicate that the two representatives are narrow band gap semiconductors (Eg 0.06-0.08 eV). Both compounds show positive Seebeck coefficients and reasonably low thermal conductivities at moderate temperatures. Cu1.5Se0.5Te0.5 is characterized by a bulk modulus of 40.9 GPa.

2.
Adv Mater ; 35(2): e2208698, 2023 Jan.
Article in English | MEDLINE | ID: mdl-36284487

ABSTRACT

A diode requires the combination of p- and n-type semiconductors or at least the defined formation of such areas within a given compound. This is a prerequisite for any IT application, energy conversion technology, and electronic semiconductor devices. Since the discovery of the pnp-switchable compound Ag10 Te4 Br3 in 2009, it is in principle possible to fabricate a diode from a single material without adjusting the semiconduction type by a defined doping level. Often a structural phase transition accompanied by a dynamic change of charge carriers or a charge density wave within certain substructures are responsible for this effect. Unfortunately, the high pnp-switching temperature between 364 and 580 K hinders the application of this phenomenon in convenient devices. This effect is far removed from a suitable operation temperature at ambient conditions. Ag18 Cu3 Te11 Cl3  is a room temperature pnp-switching material and the first single-material position-independent diode. It shows the highest ever reported Seebeck coefficient drop that takes place within a few Kelvin. Combined with its low thermal conductivity, it offers great application potential within an accessible and applicable temperature window. Ag18 Cu3 Te11 Cl3 and pnp-switching materials have the potential for applications and processes where diodes, transistors, or any defined charge separation with junction formation are utilized.

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