IJS KOLOKVIJ, Četrtek, 12. 01. 2017; ob 13. uri; dr. Tadej Rojac in dr. Goran Dražić

[Tanja Debevec]

Vabimo vas na 11. predavanje iz sklopa "Kolokviji na IJS" v letu 2016/17, ki bo v četrtek, 12. januarja 2017, ob 13. uri v Veliki predavalnici Instituta »Jožef Stefan«  na Jamovi cesti 39 v Ljubljani. Napovednik predavanja najdete tudi na naslovu http://www.ijs.si/ijsw/Koledar_prireditev, posnetke preteklih predavanj pa na http://videolectures.net/kolokviji_ijs. 

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dr. Tadej Rojac in dr. Goran Dražić

Institut Jožef Stefan in Kemijski institut

 

Električna prevodnost domenskih sten bizmutovega ferita

 

Bizmutov ferit (BiFeO3) se intenzivno raziskuje predvsem zaradi možnosti uporabe v visokotemperaturnih piezoelektričnih napravah, vendar pa je njegova uporaba omejena, saj izkazuje visoko električno prevodnost. Pomemben del te prevodnosti  izhaja iz lokalne prevodnosti na domenskih stenah. Predstavili bomo rezultate, ki dokazujejo prisotnost točkastih defektov na stenah. Z raziskavo, pri kateri smo uporabili najmodernejši presevni elektronski mikroskop, smo razložili mehanizem p-tipa električne prevodnosti domenskih sten v BiFeO3 in prispevali manjkajoči člen pri razlagi prevodnosti domenskih sten v feroelektrikih. Z istočasnim razvojem dveh analitskih mikroskopskih metod smo ugotovili, da so ti točkasti naboji dveh vrst in sicer elektronske luknje, povezane s prisotnostjo železovih ionov v 4+ oksidacijskem stanju, in vrzeli na bizmutovih mestih v kristalni rešetki. Nadalje smo pokazali, da je lokalno prevodnost domenskih sten moč prilagajati s spreminjanjem atmosfere med visokotemperaturno pripravo materiala. Raziskava bo omogočila nadaljnji razvoj materialov s kontroliranimi lokalnimi prevodnimi lastnostmi za uporabo v senzorjih, aktuatorjih, ultrazvočnih pretvornikih in tudi v nano-elektroniki prihodnosti.

Predavanje bo v angleščini.

Lepo vabljeni!

 

 

 




We invite you to the11th Institute colloquium in the academic year 2016/17. The colloquium will be held on Thursday, January 12, 2017 at 1 PM in the main Institute lecture hall, Jamova 39, Ljubljana. To read the abstract click  http://www.ijs.si/ijsw/Koledar_prireditev. Past colloquia are posted on  http://videolectures.net/kolokviji_ijs.

 

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dr. Tadej Rojac in dr. Goran Dražić

Jožef Stefan Institute and National Institute of Chemistry

 

Domain wall conduction in bismuth ferrite

 

 

Ferroelectric bismuth ferrite has been extensively studied as a candidate material for high-temperature piezoelectric devices. One of the drawbacks of this material is its high electrical conductivity which mostly stems from the local conduction at the domain walls.  Mobile charged defects, accumulated at the domain walls to screen polarization charges, have been proposed in several ferroelectrics as the origin of this local conduction, however, the presence of defects has not yet been directly confirmed. Using state-of-the-art aberration corrected electron microscopy, we explained the p-type conduction mechanism at the domain walls of bismuth ferrite and thus contributed the missing piece for explaining domain-wall conduction in ferroelectrics. We elaborated two analytical methods allowing chemical analysis at the atomic scale, which lead to identification of iron (IV) ions and bismuth vacancies accumulated at the domain walls. Iron (IV) ions in bismuth ferrite are associated with electron holes, thus leading to p-type hopping conduction at the domain walls. We further showed that the local domain-wall conductivity can be tailored by controlling the atmosphere during high-temperature annealing. The results open up possibilities for engineering local conductivity in ferroelectrics thus advancing the development of ferroelectric materials for sensors, actuators, ultrasound transducers and even nanoelectronics.

 

Cordially invited!

 

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