Svein Stølen

• Pishahang, Mehdi; Mohn, Chris Erik & Stølen, Svein (2016). Density functional study on redox energetics of LaMO3-δ(M=Sc-Cu) perovskite-type oxides. Journal of Solid State Chemistry. ISSN 0022-4596. 233, p. 62–66. doi: 10.1016/j.jssc.2015.10.013. Full text in Research Archive Show summary

  This study evaluates the redox energetics of LaMO3−δ (M=Sc–Cu) perovskite-type oxides via generalized gradient approximation (GGA) to DFT. Two different approaches to redox energetics of oxygen deficient perovskites of strongly non-stoichiometric (δ=0.5) and dilute defect limits (δ→0) are studied. In the first approach the enthalpies of oxidation are calculated using the stoichiometric end-compounds of LaMO3 and LaMO2.5. The most common structures for the reduced lanthanides and strontides similar to the ones experimentally reported for SrMnO2.5, SrFeO2.5, and LaNiO2.5 are considered. The second approach to the oxidation enthalpies termed (δ→0) follow the trend observed experimentally. This approach represents the experimental conditions of the measured oxygen enthalpies, and is hampered less by the artificial features due to spurious self-interaction errors in GGA.

• Pishahang, Mehdi; Bakken, Egil; Stølen, Svein; Thomas, Christopher Ian & Dahl, Paul Inge (2013). Oxygen non-stoichiometry, redox thermodynamics, and structure of LaFe1 − x Co x O3 − δ. Ionics (Kiel). ISSN 0947-7047. 19(6), p. 869–878. doi: 10.1007/s11581-012-0811-z. Full text in Research Archive Show summary

  The oxygen non-stoichiometry and redox thermodynamic properties of the LaFe1 − xCoxO3 − δ system (x = 0.25 and 0.75) are studied. At low temperatures, the LaCoO3 and LaFeO3 systems show partial solid solubility. At 1,273 K (in air), both compounds are single phases and are orthorhombic and rhombohedral for x = 0.25 and 0.75, respectively. Thermogravimetry has been used to measure the oxygen non-stoichiometry versus oxygen partial pressure at three temperatures, 1,223, 1,273, and 1,323 K. Redox thermodynamic quantities are extracted directly from the oxygen non-stoichiometry curves. The extracted enthalpies of oxidation do not vary significantly with stoichiometry, and for x = 0.25 and 0.75, they are −640 ± 60 and −440 ± 60 kJ (mol O2)−1, respectively. Ideal solid solution thermodynamic models are used to analyze the redox mechanisms.

• Pishahang, Mehdi; Bakken, Egil; Stølen, Svein; Larring, Yngve & Thomas, Christopher Ian (2013). Oxygen non-stoichiometry and redox thermodynamics of LaMn1−xCoxO3−δ. Solid State Ionics. ISSN 0167-2738. 213, p. 49–57. doi: 10.1016/j.ssi.2012.10.009. Full text in Research Archive Show summary

  An experimental study of the oxygen non-stoichiometry and redox thermodynamics of LaMn1 − xCoxO3 ± δ (x = 0.25 and 0.75) is presented. The system shows partial solid solubility of LaCoO3 in LaMnO3 and vice versa. While both samples consist of two phases at room temperature, quenching experiments show that the x = 0.25 sample is single phase at high temperatures for the whole range of study, 0.6 < − log(pO2/atm) < 14. The x = 0.75 sample consist of two phases even at high temperatures. This does not necessarily represent a problem for applications, and both samples are studied in details. The oxygen non-stoichiometry versus oxygen partial pressure are measured at three temperatures of 1223, 1273, and 1323 K by coulometric titration and thermogravimetry, for x = 0.25 and 0.75, respectively. The extracted enthalpies of oxidation do not vary significantly with stoichiometry, and are − 680 ± 40 and for x = 0.25 and 0.75, respectively. These data and analyses of literature data for LaMnO3 and LaCoO3 show that the enthalpy of oxidation varies nearly linearly with x. Solid solution thermodynamic models are used to analyze the redox mechanism.

• Pishahang, Mehdi; Bakken, Egil & Stølen, Svein (2012). A novel coulometric titration setup Principals, design and leakage minimization. Thermochimica Acta. ISSN 0040-6031. 543, p. 137–141. doi: 10.1016/j.tca.2012.05.020. Full text in Research Archive Show summary

  This article presents a new coulometric titration setup and describes the principles of operation, the main precautions to be taken into account to reduce the systematic errors, and evaluates the working range and the accuracy of the measurements. The major source of error, the oxygen leakage, is studied in detail and modeled based on leakage of oxygen through the YSZ solid electrolyte. Decreasing the difference in chemical potential of oxygen between inside and outside of the cell is studied as an applied measure to decrease the oxygen leakage. Flushing the pumping solid electrolyte by N2 shows a reasonable improvement. Eventually, oxygen non-stoichiometry of SrFeO3−δ is measured at 1273 K in the oxygen partial pressure range of 0.6 < −log(pO2/atm) < 12. The resulting values are in good agreement with the literature.

• Pishahang, Mehdi; Mohn, Chris Erik; Stølen, Svein & Bakken, Egil (2012). DFT-study of the energetics of perovskite-type oxides LaMO3 (M = Sc–Cu). RSC Advances. 2, p. 10667–10672. doi: 10.1039/C2RA21139D. Full text in Research Archive Show summary

  The generalized gradient approximation to density functional theory is benchmarked for the calculation of formation enthalpies of lanthanide perovskite-type oxides LaMO3 (M = Sc–Cu). Three different reaction pathways (from elements, mono and sesquioxides) have been investigated and the systematic errors associated with electron correlation due to overbinding of the oxygen molecule, electron self-interaction within localized 3d states, and geometrical relaxations are analyzed by critical comparison with a large number of experimental data. Calculated formation enthalpies from elements and sesquioxides are in good agreement with experiment when the overbinding of O2 is corrected for using the Wang ad hoc factor of 131 kJ mol−1 O2. By contrast, the calculated formation enthalpies from monoxides are systematically too low which are attributable to strong self-interactions due to localized 3d states in MO. The effects of relaxation and choice of magnetic structure on the enthalpies of formation are analyzed.

• Mohn, Chris Erik; Allan, Neil & Stølen, Svein (2012). Structure of Nanoclusters on Oxide Substrates-Bi2O3 on SrTiO3. Nanoscience and Nanotechnology Letters (NNL). ISSN 1941-4900. 4(2), p. 178–181. doi: 10.1166/nnl.2012.1294. Full text in Research Archive
• Bakken, Egil; Dahl, Paul Inge; Haavik, Camilla; Stølen, Svein & Larring, Yngve (2011). Redox energetics of perovskite-related La(B(1-x)B'(x)O(3-delta) oxides where BB' is GeCo, MnCo, MnNi and CoCu. Solid State Ionics. ISSN 0167-2738. 182(1), p. 19–23. doi: 10.1016/j.ssi.2010.11.021. Full text in Research Archive
• Mohn, Chris Erik; Stølen, Svein & Kob, W (2011). Predicting the Structure of Alloys Using Genetic Algorithms. Materials and Manufacturing Processes. ISSN 1042-6914. 26(3), p. 348–353. doi: 10.1080/10426914.2011.552021. Full text in Research Archive
• Mohn, Chris Erik & Stølen, Svein (2011). Influence of the stereochemically active bismuth lone pair structure on ferroelectricity and photocalytic activity of Aurivillius phase Bi2WO6. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. 83(1). doi: 10.1103/PhysRevB.83.014103. Full text in Research Archive
• Bjørheim, Tor Svendsen; Kuwabara, Akihide; Ahmed, Istaq; Haugsrud, Reidar; Stølen, Svein & Norby, Truls (2010). A combined conductivity and DFT study of protons in PbZrO3 and alkaline earth zirconate perovskites. Solid State Ionics. ISSN 0167-2738. 181(3-4), p. 130–137. doi: 10.1016/j.ssi.2009.04.013. Full text in Research Archive
• Bjørheim, Tor Svendsen; Stølen, Svein & Norby, Truls (2010). Ab initio studies of hydrogen and acceptor defects in rutile TiO2. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 12(25), p. 6817–6825. doi: 10.1039/b925823j. Full text in Research Archive
• Hull, S; Norberg, ST; Tucker, MG; Eriksson, SG; Mohn, Chris Erik & Stølen, Svein (2009). Neutron total scattering study of the delta and beta phases of Bi2O3. Dalton Transactions. ISSN 1477-9226. p. 8737–8745. doi: 10.1039/b910484b. Full text in Research Archive
• Mohn, Chris Erik; Stølen, Svein; Norberg, ST & Hull, S (2009). Ab initio molecular dynamics simulations of oxide-ion disorder in the delta-Bi2O3. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. 80(2). doi: 10.1103/PhysRevB.80.024205. Full text in Research Archive
• Kuwabara, Akihide; Haugsrud, Reidar; Stølen, Svein & Norby, Truls (2009). Local condensation around oxygen vacancies in t-LaNbO4 from first principles calculations. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 11(27), p. 5550–5553. doi: 10.1039/b813881h. Full text in Research Archive
• Mohn, Chris Erik; Stølen, Svein & Hull, Stephen (2009). Diffusion within alpha-CuI studied using ab initio molecular dynamics simulations. Journal of Physics: Condensed Matter. ISSN 0953-8984. 21(33). doi: 10.1088/0953-8984/21/33/335403. Full text in Research Archive
• Mohn, Chris Erik; Stølen, Svein; Nordberg, Stefan T. & Hull, Stephen (2009). Oxide-ion disorder within the high temperature delta phase of Bi2O3. Physical Review Letters. ISSN 0031-9007. 102, p. 155502-1–155502-4. Full text in Research Archive
• Allan, N.L.; Stølen, Svein & Mohn, Chris Erik (2008). Think locally - linking structure, thermodynamics and transport in grossly nonstoichiometric compounds and solid solutions. Journal of Materials Chemistry. ISSN 0959-9428. 18, p. 4124–4132. doi: 10.1039/b806156d. Full text in Research Archive
• Mohn, Chris Erik & Stølen, Svein (2007). Average and local structure of alpha-CuI by configurational averaging. Journal of Physics: Condensed Matter. ISSN 0953-8984. 19. doi: 10.1088/0953-8984/19/46/466208. Full text in Research Archive

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• Stølen, Svein (2011). En cocktail av kjemikalier. Cappelen Damm AS. ISBN 9788202346812. 200 p. Full text in Research Archive

View all works in NVA

• Stølen, Svein (2025). Panel: Higher education from access to transformation. Full text in Research Archive
• Stølen, Svein (2025). Science4Impact: Økosystemer for kunnskapsdeling med Svein Stølen - Klimaoptimistene | Podcast on Spotify. Full text in Research Archive Show summary

  Listen to this episode from Klimaoptimistene on Spotify. – Hjernekraft er den nye oljen. Kunnskap er vår viktigste ressurs for å bygge et bærekraftig samfunn og sikre konkurransekraften vår, sier Svein Stølen. I denne episoden av Science4Impact møter vi Svein Stølen, professor i kjemi og tidligere rektor ved Universitetet i Oslo. Han jobber med å bygge økosystemer der ulike aktører samspiller tettere, både nasjonalt og internasjonalt, for å styrke kunnskapsdeling, innovasjon og bærekraftig verdiskaping. Stølen forteller om initiativene Oslo Science City, Global University Academy og Senter for global bærekraft, og hvordan slike allianser kan bidra til både sosial utvikling, grønn omstilling og ny næringsvekst. #Science4Impact bygger bro mellom forskning og næringsliv for å styrke grønn konkurransekraft og ledes av Bjørn Kjærand Haugland, administrerende direktør i Skift!God lytting!

• Stølen, Svein (2025). Panel: Higher Education in Emergencies: Unlocking the Potential and Rebuilding Futures. Full text in Research Archive
• Stølen, Svein (2025). Panel: UNESCO: What mandate for tomorrow? Full text in Research Archive
• Stølen, Svein (2025). Panel: Internationalization in higher education: fostering solidarity across borders. Full text in Research Archive
• Stølen, Svein & Knarud, Marianne (2025). Panel: Hybrid education in refugee camps; providing skills and knowledge and delivering equitable futures for refugee youth. Full text in Research Archive
• Stølen, Svein (2025). Panel: Learning to earning: Developing well-structured education pathways. Full text in Research Archive
• Stølen, Svein (2025). Panel: Mobilizing university leadership in refugee education: Building a solidarity movement for greater access to higher education. Full text in Research Archive
• Stølen, Svein & Knarud, Marianne (2025). Panel: The ecosystem for digital cooperation in development. Full text in Research Archive
• Stølen, Svein (2025). Panel: Staying together, moving forward: SDG research in a divided world. Full text in Research Archive
• Knarud, Marianne & Stølen, Svein (2025). Svein Stølen og Marianne Knarud: Utdanning som løsning i fremtidens bistandspolitikk. Full text in Research Archive Show summary

  UTDANNING: Det er behov for en helt ny tilnærming og «ut av boksen»-tenkning. Vi må øke samarbeidet mellom akademia, næringsliv og humanitære organisasjoner.

• Knarud, Marianne & Stølen, Svein (2025). HE for displaced people is a collective responsibility. Full text in Research Archive Show summary

  In this age where almost 130 million people are forcibly displaced, ensuring higher education reaches refugee communities is vital if we are serious a...

• Kolshus, Thorgeir & Stølen, Svein (2024). Minneord Thomas Hylland Eriksen. p. 50–50. Full text in Research Archive
• Brekke, Camilla; Stølen, Svein; Reigstad, Marit; Petersson, Eivind Vad; Håverstad, Thor Arne & Skatteboe, Rolf [Show all 7 contributors for this article] (2023). FRA HVITT TIL BLÅTT: KUNNSKAP OG FORVALTNING AV FRAMTIDENS POLHAV. Full text in Research Archive Show summary

  I løpet av de neste 30 årene vil nye varmerekorder gjøre det hvite Polhavet blått og åpent om sommeren. De lokale og globale konsekvensene er ukjente, men trolig store. Norge bør sette av minst ti år og en milliard kroner til vårt største forskningsprosjekt noensinne. Målet er å forberede oss og resten av verden på et blått Polhav. Norge er den arktiske havnasjonen med tradisjonen, erfaringen, infrastrukturen - og dermed et ansvar - for at verden skal forstå og forberede seg på denne store naturendringen. Framtidens Polhav er et nasjonalt faglig initiativ som utvikles for å løfte kunnskapen om klima, miljø, politikk og ressursutviklingen i Polhavet i årene som kommer. Konsortiet bak initiativet består av 16 institusjoner: Akvaplan-niva, FFI, FNI, Havforskningsinstituttet, Meteorologisk institutt, NERSC, NGU, NORCE, Norsk Polarinstitutt, NTNU, NUPI, SINTEF, UiB, UiO, UiT og UNIS.

• Remonato, Filippo; Rana, Shahzad; Stølen, Svein; Gjul, Gunn Karin; Lødrup, Julie & Melsom, Nina [Show all 7 contributors for this article] (2023). Hva gjør kunstig intelligens med morgendagens arbeidsliv? [Internet]. Kulturhuset Oslo. Full text in Research Archive
• nrk, Dagsnytt atten; Holden, Lars; Stølen, Svein & Moe, Ola Borten (2022). Krisen i Forskningsrådet. [TV]. NRK. Full text in Research Archive
• Aryeetey, Ernest; Engebretsen, Eivind; Gornitzka, Åse; Maassen, Peter & Stølen, Svein (2020). Vaccine inequities expose fault lines in North-South collaboration. University World News. Full text in Research Archive
• Aryeetey, Ernest; Engebretsen, Eivind; Gornitzka, Åse; Maassen, Peter & Stølen, Svein (2020). A step backwards in the fight against global vaccine inequities. The Lancet. ISSN 0140-6736. 397(10268). doi: 10.1016/S0140-6736(20)32596-4. Full text in Research Archive
• Furevik, Tore; Halvorsen, Kristin; Skålin, Roar; Johnny, Johannessen; Nygaard, Kari & Støle, Elisabeth Maråk [Show all 13 contributors for this article] (2020). Tre uomtvistelige fakta. Aftenposten (morgenutg. : trykt utg.). ISSN 0804-3116. Full text in Research Archive
• Eide, Hans A; Fotland, Margaret Louise; Kvale, Live Håndlykken; Stangeland, Elin; Stølen, Svein & Thomassen, Gard O Sundby [Show all 7 contributors for this article] (2015). Sharing and Storing Research Data A 4-level model of the Data flow. Full text in Research Archive
• Dick, Gunnar; Stølen, Svein & Brautaset, Trygve (2015). Digital Storsatsing. [Journal]. Populær vitenskapelig bilag- Vitenskap og Historie. Full text in Research Archive
• Mohn, Chris Erik; Stølen, Svein & Hull, Stephen (2012). Comment on "Dynamic Correlation between Superionic Coppers in alpha-CuI". Journal of the Physical Society of Japan. ISSN 0031-9015. 81(10). doi: 10.1143/JPSJ.81.106001. Full text in Research Archive
• Stølen, Svein (2011). Duftende kjemi. [Journal]. NTB-sak; diverse aviser. Full text in Research Archive
• Stølen, Svein (2011). Kjemi i hverdagen. Full text in Research Archive
• Stølen, Svein (2011). Formidling på norsk - en utfordring? Full text in Research Archive
• Stølen, Svein (2011). En cocktail av kjemikalier. Full text in Research Archive
• Stølen, Svein (2011). Boklansering - en cocktail av kjemikalier. [TV]. NRK Morgennytt. Full text in Research Archive
• Kaas, Astrid Waaler & Stølen, Svein (2011). Fra pengsesluket nederst på Blindern til ufortjent mye ros. Full text in Research Archive
• Stølen, Svein (2011). Ikke best - hvorfor og hva så? Forskningspolitikk. ISSN 0333-0273. Full text in Research Archive
• Stølen, Svein (2011). En cocktail av kjemikalier. Full text in Research Archive
• Stølen, Svein (2011). En cocktail av kjemikalier. Full text in Research Archive
• Stølen, Svein (2011). Formelen for god smak. [Journal]. NTB-sak; Sunnmørsposten og diverse andre lokalaviser. Full text in Research Archive
• Stølen, Svein (2011). Vaskeekte vitenskap. [Journal]. NTB-sak; Dagsavisen og diverse lokalaviser. Full text in Research Archive
• Stølen, Svein (2011). Kjemi mot kladdeføre. [Radio]. NRK P1 EKKO. Full text in Research Archive
• Stølen, Svein (2011). Skismøring. [Radio]. Østlandssending. Full text in Research Archive
• Stølen, Svein (2011). Kjemitimen - et antall innslag spredd over flere uker (lukt, kjemi og afrodisiaka; parfyme; selvrensende vinduer og rent vann). [Radio]. P4 - Radiokompaniet. Full text in Research Archive
• Stølen, Svein (2011). Din daglige dose kjemi. [Journal]. NTB-sak; Dagsavisen + flere lokalaviser. Full text in Research Archive
• Stølen, Svein (2011). Nanoteknologi. Full text in Research Archive
• Stølen, Svein (2011). Kjemiåret: en cocktail av kjemikalier. Naturfag. ISSN 1504-4564. p. 66–70. Full text in Research Archive
• Stølen, Svein (2010). Champagne. [Radio]. NRK Østlandssendingen. Full text in Research Archive
• Stølen, Svein (2010). Materials and renewable energy. p. 82–82. Full text in Research Archive
• Stølen, Svein (2010). Cracking the energy code. p. 83–83. Full text in Research Archive
• Stølen, Svein (2010). Erfaringer med risikovurdering. Full text in Research Archive
• Stølen, Svein (2010). Varierende arbeidsmengde. Aftenposten (morgenutg. : trykt utg.). ISSN 0804-3116. Full text in Research Archive
• Stølen, Svein (2010). Hva er hydrogenperoksid? [Journal]. Dagens Næringsliv. Full text in Research Archive
• Stølen, Svein (2009). Periodesystemet.no - hva, hvorfor, hvordan og hva så? Full text in Research Archive
• Stølen, Svein (2009). Periodesystemet.no - hva, hvorfor, hvordan og hva så? Full text in Research Archive
• Bjørheim, Tor S; Stølen, Svein & Norby, Truls (2009). Hydrogen in rutile TiO2: A DFT study. Full text in Research Archive
• Selbekk, Rune S & Stølen, Svein (2009). Periodesytemet.no. Stein. ISSN 0802-9121. 36(3), p. 17–19. Full text in Research Archive
• Stølen, Svein & Sagstuen, Einar (2009). Budsjettkutt truer klimadrøm. Dagens næringsliv. ISSN 0803-9372. Full text in Research Archive
• Stølen, Svein & Sagstuen, Einar (2009). Finansieringsordning truer miljøforskningen. [Journal]. Uniforum. Full text in Research Archive
• Stølen, Svein (2009). Hvordan koke det perfekte egg til påske. [Radio]. NRK P2, Verdt å vite. Full text in Research Archive
• Stølen, Svein (2008). Skal det være en cocktail av kjemikalier? Full text in Research Archive
• Stølen, Svein (2008). An introduction to first principles computational mineralogy and mineral physics. Full text in Research Archive
• Stølen, Svein (2008). Kjemikalier i hverdagen. Full text in Research Archive
• Stølen, Svein (2008). periodesystemet.no. Full text in Research Archive
• Bjørheim, Tor S; Kuwabara, Akihide; Ahmed, Istaq; Haugsrud, Reidar; Stølen, Svein & Norby, Truls (2008). A combined conductivity and DFT study of protons in PbZrO3 and AZrO3 (A=Ca,Sr,Ba). Full text in Research Archive
• Stølen, Svein (2008). 7 kjemi-innslag i Nitimen i forbindelse med 17 mai. [Radio]. NRK P1. Full text in Research Archive
• Stølen, Svein (2008). Urban gruvedrift. [Radio]. Verdt-å-vite, NRK P2. Full text in Research Archive
• Stølen, Svein (2008). Sommerkjemi - en serie i Reiseradioen sommeren 2008 (et 20-tall innslag). [Radio]. NRK P1. Full text in Research Archive
• Stølen, Svein (2008). Skal det være en cocktail av kjemikalier. Full text in Research Archive
• Trønnes, Reidar G; Boffa-Ballaran, T; Frost, DJ; Balic-Zunic, T; Olsen, L.A. & Stølen, Svein (2008). Phase relations, crystal chemistry and elasticity of perovskite and post-perovskite in CaIrO3-based analogue systems. Full text in Research Archive
• Trønnes, Reidar G; Boffa-Ballaran, T; Frost, DJ; Balic-Zunic, T; Olsen, L.A. & Stølen, Svein (2008). Phase relations and mineral physics of the lowermost mantle - the analogue compositional approach. Full text in Research Archive
• Stølen, Svein (2008). Lanseringen av periodesystemet.no og utstillingen Grunnstoffene - verdens byggeklosser i Galleri Sverdrup, Universitetsbiblioteket. [Radio]. Verdt Å Vite, NRK, P2. Full text in Research Archive
• Stølen, Svein & Mohn, Chris Erik (2008). Exploring the rough energy landscape of fast ion conductors. Full text in Research Archive
• Trønnes, Reidar G; Boffa-Ballaran, T; Frost, DJ; Balic-Zunic, T; Olsen, L.A. & Stølen, Svein (2008). The post-perovskite transition in moderate-pressure analogue systems. Full text in Research Archive
• Stølen, Svein (2008). Gull i mobiltelefoner. [TV]. NRK 21-nyhetene. Full text in Research Archive
• Tilset, Mats & Stølen, Svein (2008). Nobelprisen i Kjemi 2008. [Radio]. Verdt å vite, NRK P2. Full text in Research Archive
• Stølen, Svein (2008). Grunnstoffenes navn, Verdt-å-vite. [Radio]. NRK P2. Full text in Research Archive
• Stølen, Svein (2008). Lansering av periodesystemet.no og utstillingen Grunnstoffene - verdens byggeklosser. [TV]. Frokost TV, NRK. Full text in Research Archive
• Stølen, Svein (2008). Selvlysende fiskekaker. [Radio]. NRK P2, Verdt å vite. Full text in Research Archive
• Stølen, Svein (2008). Fra jord, luft, ild og vann til en moderne vitenskap. [Radio]. NRK P2, Verdt å vite. Full text in Research Archive
• Stølen, Svein (2008). 13 kunnskapskorn i løpet av våren 2008. [Radio]. NRK P2, Verdt å vite. Full text in Research Archive
• Stølen, Svein (2008). periodesystemet.no - hva, hvorfor, hvordan og hva så. Full text in Research Archive
• Stølen, Svein (2008). Arsenikk. [Radio]. NRK P2, Verdt å vite. Full text in Research Archive
• Stølen, Svein; Gorbitz, Carl Henrik; Omtvedt, Jon Petter & Ødegaard, Knut Jørgen Røed (2008). Verdt å vite spesial: Grunnstoffene og periodesystemet. [Radio]. NRK P2. Full text in Research Archive
• Stølen, Svein (2008). 6 innslag i nitimen om grunnstoffer i forbindelse med lanseringen av periodesystemet.no. 19 til 26 februar. [Radio]. Nitimen, NRK P1. Full text in Research Archive
• Stølen, Svein; Leifsen, Torben; Endestad, Tor; Christiansen, Torgeir; Miøen, Tore & Jensenius, Alexander Refsum [Show all 13 contributors for this article] (2015). Dataeksplosjonen - en stor utfordring, og en gedigen mulighet! Rapport fra arbeidsgruppen «Lagring og deling av forskningsdata» ved Universitetet i Oslo (UiO) 11.05.2015. Universitetet i Oslo. Full text in Research Archive
• Pishahang, Mehdi; Stølen, Svein & Bakken, Egil (2012). Redox energetics of novel perovskite-type oxygen carriers for chemical looping reforming. Universitetet i Oslo. Full text in Research Archive Show summary

  The present work focuses on the redox energetics of novel perovskite-type oxygen carriers for chemical looping reforming. The aim of this study is to increase the level of knowledge on the redox characteristics of materials for possible applications as the oxygen carriers for the chemical looping processes. Here we focus on the perovskite-type oxides (ABO3) with lanthanum on the A-site and first row transition metals on the B-site since first row transition metals normally have more than one oxidation sate, non-stoichiometry in the perovskite oxides with such metals on the B-site is common while keeping the same structure. The partial substitution of the cation on the Bsublattice is studied as a measure to adjust the redox energetics. In the present study partial substitution of cobalt in LaCoO3 with Mn and Fe is chosen. The redox behavior of nonstoichiometric compounds may be assessed from the variation of the oxygen nonstoichiometry with temperature and oxygen partial pressure. Thermogravimetric analyses (TGA) is used for most of the systems but in order to reach higher accuracy, specialized instruments are needed. One of the most accurate techniques to measure the oxygen nonstoichiometry is coulometric titration (CT). A novel CT setup was designed, constructed and validated. This setup was subsequently used to study the oxygen non-stoichiometry of the LaMn1-xCoxO3-δ system at 1223, 1273, and 1373 K. For the LaMn1-xCoxO3-δ system it is found that the observed oxygen non-stoichiometry curve is due to the simultaneous reduction of both manganese and cobalt on the B-sublattice and the enthalpy of oxidation values show a linear dependence by x (portion of Co). The oxygen non-stoichiometry and redox energetics of the second studied system, LaFe1-xCoxO3-δ, just similar to the previous system show no indication of the sequential reduction of the cations occupying the B-sublattice. The absolute value of the enthalpy of oxidation increases as the iron portion on the B-sublattice increases, which approves this finding. In contrast to the experimental approaches, DFT calculations might provide a cost effective tool to examine complex systems and obtain an approximation for the redox thermodynamic properties; according to the following reaction: 4LaBO2.5 + O2 = 4LaBO3. It is however necessary to examine the sources of error and the accuracy of the calculations. Therefore a benchmark study was conducted on the formation energetics of lanthanide first row transition metal perovskite-type oxides (LaBO3). The benchmark shows that although fundamental errors in the GGA affect the energetics, still with addition of ad hoc corrections, it is possible to obtain values which are in good agreement with the experiment. The benchmark also confirms that as long as the calculations are spin polarized (with any magnetic structure) and performed with the relaxation of the experimental crystal structure, the total energies are reproduced within 15 kJ/(mol B). Turning to the reduced phases, LaBO2.5, the calculations proved to be much more difficult than the oxidized phases. In contrast with LaBO3 phases, a bigger fraction of total energy of the reduced phases is attributed to the magnetic configuration, meaning that a simple magnetic structure (e.g. ferromagnetic) does not predict the ground state reasonably. Still, the biggest challenge is due to the configuration of oxygen vacancies on the oxygen sublattice. Simultaneous presence of oxygen vacancy and spin configurations necessitates a computational algorithm based on statistics, e.g. Monte Carlo method, which was out of the scope of this study given the three year time frame. This however opens up an opportunity for the future works.

• Bjørheim, Tor Svendsen; Norby, Truls Eivind; Haugsrud, Reidar & Stølen, Svein (2012). Hydrogen in oxides : first principles and experimental studies of incorporation, complex formation, exotic species, and transport properties. Universitetet i Oslo. Full text in Research Archive
• Fjeld, Harald; Norby, Truls; Haugsrud, Reidar & Stølen, Svein (2010). Ionic transport in atomic and nanodimensional structures in oxides. Universitetet i Oslo. Full text in Research Archive Show summary

  Oxides with high ionic conductivity represent a class of functional materials with characteristics suitable for electrochemical energy converters, such as fuel cells and batteries. This work addresses effects from changes in crystal structure and of grain boundaries on the ionic transport properties in different oxide materials. Defects are a prerequisite for transport of charged species in solids, and in this thesis defect chemistry is the theoretical foundation. The first part describes the formation of defects and important aspects for the transport of charged species in the grain interior of oxides. Relevant literature is reviewed in the second part, emphasising various effects of interfaces on transport processes. The gradual change in the crystal structure of the high temperature proton conductor LaNbO4 through a second order phase transition and its relation to the activation enthalpy of mobility of protons were studied by means of first principles calculations and conductivity measurements. Above the transition temperature, the proton conductivity curve displayed Arrhenius-type behaviour, yielding an activation enthalpy of the mobility of protons of 35 kJ/mol. At the onset of and through the second-order phase transition the conductivity dropped off steeply, followed by a less steep decrease towards lower temperatures. This was interpreted as a gradual increase in the activation enthalpy with increasing degree of distortion of the crystal structure, reaching ~ 57 kJ/mol at 205 °C. The experimentally determined values were in agreement with the computational investigation, where activation enthalpies were determined to 39 and 60 kJ/mol in tetragonal and monoclinic LaNbO4, respectively. The intrinsic transport properties of the grain boundaries in many ceramics have previously been accounted for by a space-charge model. The model predicts depletion of positive charge carriers and accumulation of negative charge carriers in the space-charge layers adjacent to a positively charged core, which explains why many ionic conductors exhibit high intrinsic grain boundary resistance. Here, we have applied the model to analyse the transport properties of the grain boundaries in BaZrO3, LaNbO4 and Er2Ti2O7 (all acceptor doped). The pO2-dependencies of the conductivity of acceptor doped BaZrO3 indicated dominating ionic and mixed ionic and p-type electronic conduction for the grain interior under reducing and oxidizing conditions, respectively, while the grain boundaries showed an additional n-type electronic contribution under reducing conditions. Transmission electron microscopy revealed enrichment of Y in the grain boundary region. These findings indicate the existence of space-charge layers in the grain boundaries. Assuming a constant level of acceptors through the space-charge layer (the so-called Mott-Schottky approximation), a space-charge potential of 0.5–0.6 V was obtained at 250 °C in wet oxygen. An increase in the grain boundary conductivity upon a D to H isotope exchange under isothermal conditions, and a positive pH2O dependency after quenching from different pH2O made us conclude that protons were the major charge carrier in the grain boundaries of acceptor doped LaNbO4. The higher functional pH2O dependency of the conductivity of the grain boundaries as compared to grain interior suggested that protons were relatively more predominating as charge carriers in the grain boundaries than in the grain interiors. This behaviour was rationalised by noting that in the space-charge layers, doubly charged oxygen vacancies exhibit a quadratic decay compared to singly charged protons. Using a Mott-Schottky approximation, a space-charge potential of 0.66 V was obtained at 250 °C for this material. The electrical properties of ceramics of (Er1-xCax)2Ti2O7-x (x = 0.02 and 0.005) with low and high contents of Si impurities at the grain boundaries were investigated by impedance spectroscopy as a function of pO2, pH2O and pD2O in the temperature range 300 – 800 °C. For the grain interior, oxygen vacancies are the major charge carrier, with protons as a minor contributor at the lower temperatures. In the grain boundaries – as compared to grain interior – the singly charged protons were relatively more predominating than the doubly charged oxygen vacancies, again suggesting that negatively charged space-charge layers govern the electrical properties. In support of this, the samples with a lower content of Si in the grain boundaries exhibited an electrical response essentially similar to those containing more Si and even a secondary Si-rich phase. The electrical response of Er2Ti2O7 contained an additional impedance – the third in the Nyquist plots – which was suggested to be caused by chemical polarization of the mixed oxide ion and proton conducting grain interiors induced by blocking of oxygen vacancies at the grain boundaries. This was supported by the tear-drop shape of this contribution, the different response on the characteristic frequency when changing either pH2O or the hydrogen isotope in the surrounding gas, and a good agreement between the experimentally and calculated value for the chemical capacitance. All together, the electrical characterisations which were carried out on BaZrO3, LaNbO4 and Er2Ti2O7 suggest that the grain boundary core-space-charge layer model can be well applied to oxides that conduct protons. The theory of chemical polarization induced by grain boundaries was applied on Er2Ti2O7, which, as we see it, provides a first application of this theory on a mixed oxide ion and protonic conductor.

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