Blar i Fakultet for naturvitenskap (NV) på forfatter "Walker, Julian"
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Advantages and challenges of hafnia-zirconia based ferroelectric random-access memories
Muszko, Daniel (Bachelor thesis, 2023)Siden oppdategelsen av ferroelektrisitet i fluorittstruktur oksider, slik som hafnia og zirkonia i 2011, har de tiltrukket seg økt interesse. En av de mest lovenede bruksområdene for disse materialene er ikke-flyktige ... -
Cation Disorder in Ferroelectric Ba4M2Nb10O30 (M = Na, K, and Rb)Tetragonal Tungsten Bronzes
Nylund, Inger-Emma; Løndal, Nora Statle; Walker, Julian; Vullum, Per Erik; Einarsrud, Mari-Ann; Grande, Tor (Journal article; Peer reviewed, 2022) -
Centrosymmetric Tetragonal Tungsten Bronzes A4Bi2Nb10O30 (A = 2 Na, K, Rb) with a Bi 6s Lone Pair
Nylund, Inger-Emma; Zeiger, Caren Regine; Peng, Ding; Vullum, Per Erik; Walker, Julian; Einarsrud, Mari-Ann; Grande, Tor (Peer reviewed; Journal article, 2022)A first-principles study of the tetragonal tungsten bronze (TTB) K4Bi2Nb10O30 has suggested that the Bi 6s lone pair causes in-plane polarization (within the a–b plane), corresponding to the one found in Pb5Nb10O30 (PN), ... -
Effects of material structure on the electrical properties of ferroelectric plastic crystal tetramethylammonium bromotrichloroferrate(III)
Løndal, Nora Statle (Master thesis, 2020)Ferroelektriske materialer er foretrukne i en rekke applikasjoner, slik som mobiltelefoner, medisinsk ultralyd og digitalt minne, på grunn av at de har elektrisk polarisasjon som kan endre retning. Metalloksider, som er ... -
Electric field dependent polarization switching of tetramethylammonium bromotrichloroferrite(III) ferroelectric plastic crystals
Walker, Julian; Sherrer, Simon; Løndal, Nora Statle; Grande, Tor; Einarsrud, Mari-Ann (Peer reviewed; Journal article, 2020)Tetramethylammonium bromotrichloroferrate(III) ([N(CH3)4][FeBrCl3]) is a plastic crystal ferroelectric with small dielectric constant <20 and piezoelectric coefficient as high as 110 pC/N. Here, super-coercive hysteresis ... -
Magnetic contributions in multiferroic gadolinium modified bismuth ferrite ceramics
Walker, Julian; Mirjanic, Anja; Sadl, Uros; Condurache, Oana Andreea; Bencan, Andreja; Rojac, Tadej; Grigoras, Marian; Uršič, Hana (Peer reviewed; Journal article, 2020)Bi0.88Gd0.12FeO3 multiferroics are of interest for next-generation electronics and are shown with a remnant magnetization 0.2 emu·g−1, coercive field 8 kOe, Curie temperature 370 °C and magnetization of 0.7 emu·g−1 at ... -
Mesophase Transitions in [(C2H5)4N][FeBrCl3] and [(CH3)4N][FeBrCl3] Ferroic Plastic Crystals
Walker, Julian; Marshall, Kenneth Paul; Beceiro, Jorge Salgado; Williamson, Benjamin; Løndal, Nora Statle; Castro-Garcia, Socorro; Andújar, Manuel Sánchez; Selbach, Sverre Magnus; Chernyshov, Dmitry; Einarsrud, Mari-Ann (Peer reviewed; Journal article, 2022)Plastic crystals are supramolecular materials that possess a unique high entropy mesophase at elevated temperatures, where a long-range structural symmetry coexists with a local molecular orientational disorder. The ... -
Modelling of the vertical deflection of ferroelectric bending tongues loaded at their free end
Cardoletti, Juliette; Radetinac, Aldin; Thiem, Daniel; Walker, Julian; Komissinskiy, Philipp; Xu, Bai-Xiang; Schlaak, Helmut; Trolier-Mckinstry, Susan E; Alff, Lambert (Peer reviewed; Journal article, 2019)In this work, a model to describe the vertical deflection of ferroelectric bending tongues with a load at their free end is proposed. The model is based on the ferroelectric switching criterion developed by Hwang et al. ... -
Poling-induced inverse time-dependent microstrain mechanisms and post-poling relaxation in bismuth ferrite
Liu, Lisha; Rojac, Tadej; Kimpton, Justin; Walker, Julian; Makarovic, Maja; Li, Jing-Feng; Daniels, John E. (Peer reviewed; Journal article, 2020)Domain-wall dynamics under strong, super-coercive electric fields in polycrystalline bismuth ferrite (BiFeO3) are not well established due to the experimental difficulties in processing high phase purity perovskite with ... -
Predicting phase transitions and rotational dynamics in the plastic crystals [(CH3)4N][FeCl4] and [(CH3)4N] [FeBr4] by using ab initio molecular dynamics with machine learned force fields
Meltzer, Sunniva (Master thesis, 2023)Plastiske krystaller er en ny materialklasse med glimrende piezoelektriske og ferroelektriske egenskaper, i tillegg til å være myke og fleksible grunnet rotasjonsfriheten til molekylene. Dette gjør dem til lovende kandidater ... -
Residual Stress and Ferroelastic Domain Reorientation in Declamped {001} Pb(Zr0.3Ti0.7)O3 Films
Denis-Rotella, Lyndsey M.; Esteves, Giovanni; Walker, Julian; Zhou, Hanhan; Jones, Jacob L.; Trolier-Mckinstry, Susan (Peer reviewed; Journal article, 2021)Ferroelectric films are often constrained by their substrates and subject to scaling effects, including suppressed dielectric permittivity. In this work, the thickness dependence of intrinsic and extrinsic contributions ... -
Solid Solution Engineering of Hybrid Supramolecular Tetraethylammonium and Tetrabutylammonium Compounds
Eknes, Elise (Master thesis, 2022)Plastiske krystaller er supramolekylære materialer som gjennomgår en fasetransformasjon til en mesofase ved forhøyede temperaturer. I mesofasen har molekylene eller ionene rotasjonell frihet samtidig som de er begrenset ... -
Solid state phase transition materials for thermal energy storage - A review on the potential and limitations of solid-solid phase change materials for latent thermal energy storage
Haraldsen, Rikke Holte (Bachelor thesis, 2023)Termisk energilagring spiller en viktig rolle i utviklingen av en mer bærekraftig fremtid, og fastfase faseendringsmaterialer for latent termisk energilagring har et stort potensial i denne utviklingen. Latent varmelagring ... -
Solid-solid Phase Change Material Pentaerythritol as a Latent Heat Storage Material in Domestic Cooking Stoves
Ramberg, Magnus Bengt Inge (Master thesis, 2023)Et økende energiforbruk har ført termisk energilagring i rampelyset. Blant ulike tilnærminger i termisk energilagring skiller latent varmelagring seg ut, der varmen lagres ved hjelp av en reversibel faseovergang i et ... -
Structure and phase transitions of A2MBr4 supramolecular crystals where A=[N(CH3)4] and/or [N(C2H5)4] and M= Zn or Mn
Fagerheim, Kristine (Master thesis, 2021)Behovet for mindre, mer bærekraftige og elastiske elektriske innretninger har økt interessen for å finne erstatninger for konvensjonelle ferroelektriske materialene som ofte er sprø og har en lite energieffektiv produksjon. ... -
Super-coercive electric field hysteresis in ferroelectric plastic crystal tetramethylammonium bromotrichloroferrate(III)
Walker, Julian; Miranti, Rany; Skjærvø, Susanne Linn; Rojac, Tadej; Grande, Tor; Einarsrud, Mari-Ann (Peer reviewed; Journal article, 2020)Ionic plastic crystals are part of an emerging class of hybrid organic–inorganic ferroelectrics. The combination of low dielectric constants (<20), strong piezoelectric coefficients (>100 pC N−1) and low temperature synthesis ... -
Synthesis and Characterisation of the Plastic Crystal Solid Solution Systems [(CH3)4N]x[(CH3CH2)4N]1-x[FeBrCl3] (x = 0.7 - 1)
Holck, Ingvild Eng (Master thesis, 2021)Gjennom deres reversible permanente polarisering har ferroelektriske materialer funnet bruksområder innen flere grener av teknologi, som for eksempel digitalt minne, filtre eller sensorer. Dagens konvensjonelle ferroelektriske ... -
Thermal Decomposition Magnetic Nanoparticles for Improvement of Selective Hyperthermia in Cancer Cells
Skjevik, Ulrik Ofstad (Master thesis, 2023)Kreft er en av de ledende dødsårsakene i samfunnet i dag, og som et resultat av dette er kreftbehandling. ment er et stort forskningsfelt. Mange nåværende kreftbehandlinger angriper kreftceller, men er også skadelige for ...