Jump to main content
Jump to site search
Access to RSC content Close the message box

Continue to access RSC content when you are not at your institution. Follow our step-by-step guide.



Defect chemistry of donor-doped BaTiO3 with BaO-excess for reduction resistant PTCR thermistor applications – redox-behaviour

Author affiliations

Abstract

The electrical conductivity of donor-doped BaTiO3 thermistor ceramics with excessive BaO revealing a reduction-persistent PTCR effect has been carefully examined depending on materials’ composition and oxygen partial pressure at moderate temperatures between 973 and 1273 K. This thermal regime represents the range which is relevant for the realization of insulating grain boundaries in these electrically inhomogeneous ceramic materials through reoxidation. Based on the experimental results strong evidence for a general correlation between the PTCR characteristics, DC-conductivity and the herewith associated defect chemistry significant to thermistor applications is presented for the system (Ba, La)mTiO3, where m designates the BaO-excess (m ≥ 1). Nominal compositions with a relatively low (Ba + La)/Ti ratio m only show a rather poor PTCR effect and an overall donor-type response in conductivity can be observed at all levels of oxygen partial pressure considered in the present study. With increasing (Ba + La)/Ti ratio m the nonlinear resistivity jump with increasing temperature strongly improves and the acceptor-type behaviour seems to dominate the total conductivity at partial pressures of oxygen above approximately 10−6 MPa. This result for compositions with high BaO-excess can be understood by the local formation of point defect associates in the grain boundary regions that consist of both acceptor-type titanium vacancies and donor-type oxygen vacancies. Their origin is attributed to the preferential local incorporation of excessive BaO into the BaTiO3 lattice at the intergranular interfaces.

Graphical abstract: Defect chemistry of donor-doped BaTiO3 with BaO-excess for reduction resistant PTCR thermistor applications – redox-behaviour

Back to tab navigation

Article information


Submitted
17 Dec 2019
Accepted
06 Mar 2020
First published
06 Mar 2020

Phys. Chem. Chem. Phys., 2020, Advance Article
Article type
Paper

Defect chemistry of donor-doped BaTiO3 with BaO-excess for reduction resistant PTCR thermistor applications – redox-behaviour

C. Pithan, H. Katsu and R. Waser, Phys. Chem. Chem. Phys., 2020, Advance Article , DOI: 10.1039/C9CP06793K

Social activity

Search articles by author

Spotlight

Advertisements