tarjeibo

• Bondevik, Tarjei; Bjørheim, Tor Svendsen & Norby, Truls Eivind (2020). Assessing common approximations in space charge modelling to estimate the proton resistance across grain boundaries in Y-doped BaZrO3. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 22(21), s. 11891–11902. doi: 10.1039/c9cp06625j. Fulltekst i vitenarkiv
• Bondevik, Tarjei; Polfus, Jonathan Marc & Norby, Truls Eivind (2020). Disagreements between space charge models and grain boundary impedance data in yttrium-substituted barium zirconate. Solid State Ionics. ISSN 0167-2738. 353. doi: 10.1016/j.ssi.2020.115369. Fulltekst i vitenarkiv Vis sammendrag

  Although the space charge model is commonly used to explain the high grain boundary resistance in proton conducting yttrium-substituted BaZrO3, it fails in its simplest forms with factors 10–40 to fit experimental data with respect to the characteristic frequency of the grain boundary impedance. We suggest modifications to the model, somewhat improving its fit. Including trapping effects of protons near yttrium substituents reduces the error only by factors less than 1.6. Increasing the width of the grain boundary core reduces the error with factors of 1.5–3. Discretizing the space charge layer, such that protons can only reside on specific, discrete sites, reduces the error with another factor of around 2. Considering reduced proton mobility in the GB by reducing its effective area may give a reduction in the fitting error of a factor of 2. Varying the dielectric constant in the GB does not affect the error considerably. Neither each single modification, nor their combined effect, can, however, account for the majority of the discrepancy between the space charge model and experimental data.

• Bondevik, Tarjei; Kuwabara, Akihide & Løvvik, Ole Martin (2019). Application of machine learning-based selective sampling to determine BaZrO3 grain boundary structures. Computational Materials Science. ISSN 0927-0256. 164, s. 57–65. doi: 10.1016/j.commatsci.2019.03.054. Fulltekst i vitenarkiv Vis sammendrag

  A selective sampling procedure is applied to reduce the number of density functional theory calculations needed to find energetically favorable grain boundary structures. The procedure is based on a machine learning algorithm involving a Gaussian process, and uses statistical modelling to map the energies of the all grain boundaries. Using the procedure, energetically favorable grain boundaries in BaZrO3 are identified with up to 85% lower computational cost than the brute force alternative of calculating all possible structures. Furthermore, our results suggest that using a grid size of 0.3 Å in each dimension is sufficient when creating grain boundary structures using such sampling procedures.

• Bondevik, Tarjei; Ness, Heine Håland; Bazioti, Kalliopi; Norby, Truls Eivind; Løvvik, Ole Martin & Koch, Christoph T. [Vis alle 7 forfattere av denne artikkelen] (2019). Investigation of the electrostatic potential of a grain boundary in Y-substituted BaZrO3 using inline electron holography. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 21(32), s. 17662–17672. doi: 10.1039/c9cp02676b. Fulltekst i vitenarkiv Vis sammendrag

  We apply inline electron holography to investigate the electrostatic potential across an individual BaZr0.9Y0.1O3 grain boundary. With holography, we measure a grain boundary potential of −1.3 V. Electron energy loss spectroscopy analyses indicate that barium vacancies at the grain boundary are the main contributors to the potential well in this sample. Furthermore, geometric phase analysis and density functional theory calculations suggest that reduced atomic density at the grain boundary also contributes to the experimentally measured potential well.

• Dirdal, Christopher Andrew; Bondevik, Tarjei & Skaar, Johannes (2015). Relaxed dispersion constraints and metamaterial effective parameters with physical meaning for all frequencies. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. 91(13). doi: 10.1103/PhysRevB.91.134102. Fulltekst i vitenarkiv

Se alle arbeider i NVA

• Bondevik, Tarjei; Prytz, Øystein & Norby, Truls Eivind (2019). Investigation of the electrostatic potential of a grain boundary in Y-substituted BaZrO3 using inline electron holography. Fulltekst i vitenarkiv
• Bondevik, Tarjei; Norby, Truls Eivind & Bjørheim, Tor Svendsen (2018). Validating approximations commonly used in space charge modelling. Fulltekst i vitenarkiv
• Bondevik, Tarjei & Løvvik, Ole Martin (2018). Applying Machine Learning-based Selective Sampling to determine Grain Boundary Structures. Fulltekst i vitenarkiv
• Ness, Heine Håland; Bondevik, Tarjei & Prytz, Øystein (2018). Basic principle of electron holography. Fulltekst i vitenarkiv
• Norby, Truls Eivind; Min, Chen & Bondevik, Tarjei (2018). Space-charge and its effects on solid-oxide electrode kinetics. Fulltekst i vitenarkiv
• Norby, Truls Eivind; Min, Chen; Bondevik, Tarjei & Polfus, Jonathan M. (2018). Space Charge Layers and Their Role for Properties of Interfaces in Solid State Ionics. Fulltekst i vitenarkiv
• Bondevik, Tarjei (2017). Space charge layers around barium zirconate grain boundaries. Fulltekst i vitenarkiv
• Bondevik, Tarjei (2017). Space charge layers around BZY grain boundaries. Fulltekst i vitenarkiv
• Bondevik, Tarjei (2017). Investigating BaZr0.85Y0.15O3 space charge layers with density functional theory. Fulltekst i vitenarkiv
• Bondevik, Tarjei (2017). Charge separation in ceramics investigated by electron holography. Fulltekst i vitenarkiv
• Olsen, Claude R.; Bredesen, Rune; Bernuy-Lopez, Carlos; Bondevik, Tarjei & Chen, Min (2016). New generation of researchers making their mark. Fulltekst i vitenarkiv
• Bondevik, Tarjei (2019). Grain boundaries in a BaZrO3-based proton conductor: A theoretical and experimental study on atomic scale. Universitetet i Oslo. Fulltekst i vitenarkiv
• Ness, Heine Håland; Prytz, Øystein & Bondevik, Tarjei (2018). Inline Electron Holography - Theoretical and Experimental Aspects. Universitetet i Oslo. Fulltekst i vitenarkiv Vis sammendrag

  In this thesis we study a state of the art inline electron holography technique, titled Full Resolution Wave Reconstruction (FRWR). A rewiev of the reconstruction algorithm is given. We have tested the FRWR capabilities to recover the mean inner potential of Cu2O, and the potential profile across a Cu2O/CuO/ZnO heterojunction.In addition the effects of experimental setup such as objective aperture and energy filtering have been investigated. In addition, theoretical values of the mean inner potential have been calculated from following two different models, a non-binding atom model and an ionized atom model.

Se alle arbeider i NVA