Nonlinear electrical properties of grain boundaries in BaZrO3

M. Shirpour, C. T. Lin, R. Merkle, and J. Maier

Max Planck Institute for Solid State Research, Stuttgart, Germany

•• Large Large grainedgrained samplesample: Infrared Image Furnace (~2600 °C)

Feed rod

Seed rod

Molten Zone

Crystal

Quartz tube

Ellipsoidal mirror

Lamp

•• GB GB electricalelectrical propertiesproperties underunder DC DC biasbias::

•• MicrocontactMicrocontact impedanceimpedance spectraspectra of of individualindividual GBsGBs::

Microcontact setup Microelectrodes and position of needles

Impedance spectra within one grain / across one GB

Schottky barrier with interface states Schottky barrier without interface states

Thermionic emissionDrift-diffusionElectron tunnelling

Modelling on p-type SrTiO3

decrease of RGB and CGB underDC bias supports space charge model

Continuous GB secondary phase as reason for blocking GB:

- could also lead to RGB decreasing with bias(BV-analogous increase of electron/proton hopping rate)

- but constant CGB expected

* Rbulk ≈ constant (Cbulk hidden by Cstray)

* RGB decreases with applied bias

* CGB decreases with applied bias

capacitance of space charge zones:

* model with interface states:core charge increases under bias→ depletion zone broadens→ CGB decreases already at moderate bias

* model without interface states:large bias: imcomplete depletion on one side→ depletion zone broadens → CGB ⇓ Holbling, Waser,

J. Appl. Phys. 91 (2002) 3037

Emtage, J. Appl. Phys. 48 (1977) 4372

Riess, Maier, Phys. Rev. Lett. 100 (2009) 205901

Impedance spectra under DC bias: Voltage dependent GB resistance and capacitance:

•• Voltage dependent GB electrical properties explained by differenVoltage dependent GB electrical properties explained by different t models:models: