Mapping grain boundary heterogeneity at the nanoscale in a positive temperature coefficient of resistivity ceramic

Kristina M. Holsgrove, Demie M. Kepaptsoglou, Alan M. Douglas, Quentin M. Ramasse, Eric Prestat, Sarah J. Haigh, Michael B. Ward, Amit Kumar, J Marty Gregg, Miryam Arredondo-Arechavala

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)
227 Downloads (Pure)

Abstract

Despite being of wide commercial use in devices, the orders of magnitude increase in resistance that can be seen in some semiconducting BaTiO3-based ceramics, on heating through the Curie temperature (TC), is far from well understood. Current understanding of the behavior hinges on the role of grain boundary resistance that can be modified by polarization discontinuities which develop in the ferroelectric state. However, direct nanoscale resistance mapping to verify this model has rarely been attempted, and the potential approach to engineer polarization states at the grain boundaries, that could lead to optimized positive temperature coefficient (PTC) behavior, is strongly underdeveloped. Here we present direct visualization and nanoscale mapping in a commercially optimized BaTiO3 –PbTiO3 –CaTiO3 PTC ceramic using Kelvin probe force microscopy, which shows that, even in the low resistance ferroelectric state, the potential drop at grain boundaries is significantly greater than in grain interiors. Aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy reveal new evidence of Pb-rich grain boundaries symptomatic of a higher net polarization normal to the grain boundaries compared to the purer grain interiors. These results validate the critical link between optimized PTC performance and higher local polarization at grain boundaries in this specific ceramic system and suggest a novel route towards engineering devices where an interface layer of higher spontaneous polarization could lead to enhanced PTC functionality.
Original languageEnglish
Article number066105
Number of pages10
JournalAPL Materials
Volume5
Issue number6
DOIs
Publication statusPublished - 21 Jun 2017

Fingerprint Dive into the research topics of 'Mapping grain boundary heterogeneity at the nanoscale in a positive temperature coefficient of resistivity ceramic'. Together they form a unique fingerprint.

Cite this