Premium
Phase Segregation of Polymorphic Solid Ion Conducting Cu 7 PSe 6 during Thermoelectric Experiments
Author(s) -
Baumer Franziska,
Nilges Tom
Publication year - 2018
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201800108
Subject(s) - seebeck coefficient , thermoelectric effect , thermoelectric materials , materials science , ion , phase transition , electrical resistivity and conductivity , conductivity , semiconductor , phase (matter) , condensed matter physics , chemical physics , electrical conductor , conductor , optoelectronics , thermodynamics , chemistry , physics , composite material , organic chemistry , quantum mechanics
Solid ion conductors are moved into the focus of energy‐related science as thermoelectric materials due to their high ion mobility and their ability to scatter phonons. A second interesting phenomenon of some solid ion (and electron) conductors is the possibility to perform a pnp switch of their semiconductor mechanism during a structural phase transition. During our search for new pnp switching systems we examined trimorphic, argyrodite‐type Cu 7 PSe 6 as a potential candidate. Recently, this phase was reported to be a reasonable thermoelectric material, which combines to the statements given above. The ion mobility in a solid can be a beauty or a beast concerning the stability of the compound during thermoelectric operation. In this article we report on the electric conductivity and thermopower evolution of Cu 7 PSe 6 , a trimorphic, mixed ion and electron conductor. Slightly above room temperature this compound undergoes an order‐disorder phase transition where Cu tends to become almost liquid in the framework of the anions. Intending to verify the possibility of a pnp switch during this order‐disorder transition we started a systematic evaluation of the (thermo)electrochemical behavior of this phase. Unfortunately, this material does not perform a pnp switch but it also shows a well‐defined decomposition behavior upon thermoelectric cycling. In this contribution we report on the change and evolution of properties during the characterization process, which manifests in a continuous variation of the total electric conductivity and thermopower upon thermoelectric cycling. This study reflects the importance and need of stability studies of solid ion conductors in the entire range of thermoelectric application especially if order‐disorder phase transitions and high ion mobilities are present which can cause significant mass transport and phase separation within the sample.