Probing of elastic straining effect on oxygen vacancies dissociation and oxy-ion conduction mechanisms in multiple doped ceria: as electrolyte for IT-SOFCs

Please consider  the  manuscript  “Probing of elastic straining effect on oxygen vacancies dissociation and oxy-ion conduction mechanisms in multiple doped ceria: as electrolyte for IT-SOFCs” for publication in Inorganics as an original article. This manuscript or any part of it has not been published or submitted elsewhere.

Elastic strain engineering offers a new route to develop high-performance electrolytes for electrochemical energy conversion devices. In general, elastic strain in bulk materials is introduced by doping effect; size-valence mismatch of dopant incorporate the local elastic strain. Dopant induced straining effect alter energy landscape near the local strained region and create un-equilibrium site for ion diffusion. In general, functional oxides based electrolytes are more versatile systems used for electrochemical energy conversions devices like solid oxide fuel cell (SOFCs) and solid oxide electrolytes cell (SOECs).  The oxy-ion conductivity of electrolyte decides the performance of SOFCs and SOECs. In oxides, dopant induced elastic straining effect alter the diffusion kinetics by modifying the oxygen defect formation enthalpy, migration energy barrier, adsorption energy, dissociation barrier, and charge transfer barrier and thus oxy-ion conductivity. In the present attempt, we consider multiple-dopant effect in ceria systems to incorporate strain. Multiple dopant effect will give various choices for size-charge mismatch in ceria lattice. Local straining effect is monitored by EXAFS probe, multiple valence dopants effect on the variation of local surrounding in terms of coordination number and interatomic spacing at NN and NNN-site are observed. The multiple valence (trivalent-divalent) dopants i.e. CSDC, SSRDC, SNCDC and SNSRDC exhibit comparatively lower CNs and higher interatomic spacing R_Ce-O at NN than NNN-site indicate lower trapping energy of oxygen vacancies from dimer than trimer defect clustering, respectively. The trapping energy is closely related with dissociation energy of oxygen vacancies, thus activation energy of ionic conductivity. XANES spectral analysis reveal, content of Ce³⁺ over Ce⁴⁺ in doped ceria system is also function of dopant and highly suppresses for multiple doped system. Oxygen vacancies dissociation mechanism demonstrated by using Raman spectroscopy, indicate defect associated Raman modes in multiple doped ceria system is comparatively more prominent signifies aliovalence effect of multiple dopants introduced more defects in ceria lattice. Dopant induced strain-charge effect on oxygen association-dissociation mechanism and thus ionic conductivity is experimentally demonstrated by using spectroscopic tools. Conductivity of multiple doped ceria systems are found to be increased by one order as compared to singly doped ceria system. Multivalent doped ceria system has proved its ability to modulate ionic conductivity at intermediate to low temperature range.

The major trust of present study is to probe elastic straining effect due to multiple dopant in ceria lattice. There are various choices for size-valence mismatch in case of multiple dopant; which induce local strain and bond length anomalies. These results are analogous to elastic strain. The lattice site un-equilibrium surrounding to elastic strain region in ceria lattice, create low energy path for oxygen-ion hopping. Multiple doping effect lead to fine tuning of local strain and bond length anomalies in ceria lattice and thus modifies oxy-ion hopping path. Spectroscopic tools like EXAFS, XANES and Raman Spectroscopy helpful to monitor the local strain modifications. High temperature study of EXAFS, XANES and Raman Spectroscopy will monitor the local structural changes during oxygen ion hopping. Study will demonstrate size-valence influence of dopant on hopping path of oxygen ions through ceria lattice.

We  think  that  our  paper  can  appeal  to  a  broad  readership  that  are  interested  in  the  general  areas  of ionic conductivity, defect clustering, in electrochemical devices and electrolysis system. Therefore will make a very important contribution to the Inorganics.

Your’s sincerely

Smita Acharya