Research focus

Lead-free piezo-/ferroelectic materials

Ferroelectric and piezoelectric materials are used in a range of technologies that power modern society such as portable electronics, sensors, or medical appliances to name a few. However, most ferroelectric materials are based on toxic lead-containing PbZr_1-xTi_xO₃ (PZT) making this problematic. The excess of lead in ferroics is neither in line with the UN sustainable development goals nor the European Union's Restriction of Hazardous Substances (RoHS) regulations. Such regulations require the removal of hazardous substances to reduce the environmental and health impacts of electronics and their associated waste. This has driven research towards the exploration of lead-free ferro- and piezoelectric materials, in particular, towards the development of new systems within the tetragonal tungsten bronze (TTB) family. The TTB framework offers possibilities for broad compositional engineering due to the variety of lattice sites present in TTBs compared to conventional perovskites such as PZT. Using a combination of experiment and ab initio simulations, we strive to explore new lead-free TTB materials with improved ferro-/piezoelectric properties whilst providing a complete and holistic understanding of the mechanisms that underpin them.

In situ studies during hydrothermal syntesis of complex oxide materials 
Hydrothermal synthesis is a versatile method for the low temperature preparation of complex crystalline oxide materials. To study the formation of the materials we use a capillary cell to mimic the process in an autoclave. Combined with high energy X-ray synchrotron radiation, we can follow the reaction going on during the hydrothermal synthesis with high time resolution. Materials studied are lead free piezoelectric perovskites (alkali niobates, barium titanate), tetragonal tungsten bronzes (strontium barium niobates) and hexagonal manganites (yttrium manganite).

Aqueous chemical solution deposition of thin oxide films
Using the aqueous chemical solution platform we develop methodology for chemical solution deposition of oriented and epitaxial films complex oxide thin films on different types of substrates. In situ synchrotron X-ray diffraction are used to study the crystallization of the films during heating as well as study ferroic properties as a function of electrical field. In situ infrared spectroscopy during pyrolysis gives us information about the decomposition of precursors and early formation of secondary phases. In addition, total scattering is used to reveal the short-range structure all the way from the precursor to the crystalline thin film. Lead free piezoelectric perovskites (alkali niobates, barium titanate) and tetragonal tungsten bronzes (strontium barium niobates) are studied.

Hybrid nanocomposites
We are developing hybrid inorganic-organic nanocomposites for optical and high voltage insulation applications by using an in-situ sol-gel based procedure to obtain a high degree of dispersion of the nanoparticles in the polymer. The nanocomposite properties can be tailored by varying the ratio between the inorganic and organic monomers as well as the reaction conditions. Epoxy-based nanocomposites with well dispersed oxide nanoparticles are prepared showing improved properties with respect to permittivity and electrical tree growth during breakdown.

Supramolecular materials
Supramolecular inorganic-organic materials offer a possibility to limit the elemental footprint of materials by using organic cations containing only C, H and N as building blocks. These materials can easily be produced through solution precipitation and have the potential for applications in recyclable devices for electronics. We are studying the structure, phase transitions and electrical properties of plastic crystals based on tetramethylammonium and tetraethylammonium organic cations combined with inorganic anions for energy related applications in e.g., capacitors and as calorics.

We have a strong focus on the development and utilisation of in situ characterization tools besides the use of the general pool of processing and structural as well as microstructural characterization equipment at the department:

In situ capillary cell for studies of hydrothermal reactions

In situ high temperature cell for X-ray diffraction studies during chemical solution deposition of thin films

In situ high temperature IR cell for studies during chemical solution deposition of thin films

In situ high temperature capillary cell for X-ray diffraction and total scattering studies

Set-up for measurements of ferroelectric properties using interdigitated electrodes

K. Bakken, O. G. Grendal and M.-A. Einarsrud
In situ characterisation for studying nucleation and growth of nanostructured materials and thin films during liquid-based synthesis
J. Sol-Gel Sci. Technol. (2022)

I.-E. Nylund, N. S. Løndal, J. Walker, P. E. Vullum, M.-A. Einarsrud and T. Grande
Cation Disorder in Ferroelectric Ba₄M₂Nb₁₀O₃₀ (M = Na, K, and Rb) Tetragonal Tungsten Bronzes
Inorganic Chemistry (2022)

V. H. Pedersen, A. B. Blichfeld, K. Bakken, D. Chernyshov, T. Grande and M.-A. Einarsrud
Crystallization and Texturing of Sr_xBa_1–xNb₂O₆ Thin Films Prepared by Aqueous Solution Deposition─An In Situ X-ray Diffraction Study
Cryst. Growth Des. (2022)

S. L. Skjærvø, G. K. Ong, O. G. Grendal, K. H. Wells, W. van Beek, K. Ohara, D. J. Milliron, S. Tominaka, T. Grande and M.-A. Einarsrud
Understanding the Hydrothermal Formation of NaNbO₃: Its Full Reaction Scheme and Kinetics
Inorg. Chem. 60 (2021) 7632–7640

K. Marshall, S. O. Eidem, D. R. Småbråten, S. M. Selbach, T. Grande and M.-A. Einarsrud
Hydrothermal synthesis of hexagonal YMnO₃ and YbMnO₃ below 250 °C
Dalton Trans. (2021)

K.Bakken, N.H.Gaukås, O.G.Grendal ,A.B.Blichfeld, S.Tominaka, K.Ohara, D.Chernyshov, J.Glaum, T.Grande and M.-A.Einarsrud
In situ X-ray diffraction studies of the crystallization of K_0.5Na_0.5NbO₃ powders and thin films from an aqueous synthesis route
Open Ceramics 7 (2021) 100147

T. M. Reader, U. Hanke, E. Halvorsen and T. Grande
A unified approach for the calculation of in-plane dielectric constant of films with interdigitated electrodes
Smart Mater. Struct. 29 (2020) 115039

K. Bakken, A. B. Blichfeld, D. Chernyshov, T. Grande, J. Glaum and Mari-Ann Einarsrud
Mechanisms for texture in BaTiO₃ thin films from aqueous chemical solution deposition
J. Sol-Gel Sci. Technol. 95 (2020) 562–572.

E. Khomyakova, S. Wenner, K. Bakken, J. Schultheiß, T. Grande, J. Glaum and M.-A. Einarsrud
On the formation mechanism of Ba_0.85Ca_0.15Zr_0.1Ti_0.15O₃ thin films by aqueous chemical solution deposition
J. Eur. Ceram. Soc. 40 (2020) 5376-5383.

A. B. Blichfeld, K. Bakken, D. Chernyshov, J. Glaum, T. Grande and M.-A. Einarsrud
Experimental setup for high-temperature in situ studies of crystallization of thin films with atmosphere control
J. Synchrotron Radiat. 27 (2020).

J. Walker, S. Scherrer, N. S. Løndal, T. Grande and M.-A. Einarsrud
Domain switching in ferroelectric tetramethylammonium bromotrichloroferrate(III) plastic crystals
APL 116 (2020) 242902.

S. S. Aamlid, S. M. Selbach and T. Grande
Structural evolution of ferroelectric and ferroelastic barium sodium niobate tungsten bronze
Inorg. Chem. 59 (2020) 8514-8521.

K. Marshall, A. B. Blickfeld, S. L. Skjaervo, O. G. Grendal, W. van Beek, S. M. Selbach, T. Grande and M.-A. Einarsrud
A fast, low temperature synthesis method for hexagonal YMnO3: Kinetics, purity, size and shape as studied by in situ X‐ray diffraction
Chem. Eur. J. (2020).

M. M. Adnan, E. G. Tveten, R. Miranti, S. Hvidsten, M.-H. G. Ese, J. Glaum and M.-A. Einarsrud
In situ synthesis of epoxy nanocomposites with hierarchical surface-modified SiO₂ clusters
J. Sol-Gel Sci. Technol. (2020).

N. H. Gaukås, J. Glaum, M.-A. Einarsrud and T. Grande
Ferroelectric and dielectric properties of Ca²⁺-doped and Ca²⁺-Ti⁴⁺ co-doped K_0.5Na_0.5NbO₃ thin films
J. Mater. Chem. C (2020).

J. Walker, R. Miranti, S. L. Skjærvø, T. Rojac, T. Grande and M.-A. Einarsrud
Super-coercive electric field hysteresis in ferroelectric plastic crystal tetramethylammonium bromotrichloroferrate(III)
J. Mater. Chem. C 8 (2020) 3206-3216.

O. G. Grendal, I.-E. Nylund, A. B. Blichfeld, S. Tominaka, K. Ohara, S. M. Selbach, T. Grande and M.-A. Einarsrud
Controlled growth of Sr_xBa_1‐xNb₂O₆ hopper‐ and cube‐shaped nanostructures by hydrothermal synthesis
Chem. Eur. J. (2020).

O. G. Grendal, A. B. Blichfeld, T. D. Vu, W. van Beek, S. M. Selbach, Tor Grande and M.-A. Einarsrud
Composition and morphology tuning during hydrothermal synthesis of Sr_xBa_1−xNb₂O₆ tetragonal tungsten bronzes studied by in situ X-ray diffraction
CrystEngComm (2019).

N. H. Gaukås, S. M. Dale, T. M. Ræder, A. Toresen, R. Holmestad, J. Glaum, M.-A. Einarsrud and T. Grande
Controlling Phase Purity and Texture of K_0.5Na_0.5NbO₃ Thin Films by Aqueous Chemical Solution Deposition
Materials 12 (2019) 2042.

S. S. Aamlid, S. M. Selbach and T. Grande
The Effect of Cation Disorder on Ferroelectric Properties of Sr_xBa_1−xNb₂O₆ Tungsten Bronzes
Materials 12 (2019) 1156.

K.-N. Pham, N. H. Gaukås, M. Morozov, T. Tybell, P. E. Vullum, T. Grande and M.-A. Einarsrud
Epitaxial K_0.5Na_0.5NbO₃ thin films by aqueous chemical solution deposition
R. Soc. Open Sci. 6 (2019) 180989.

T. M. Raeder, K. Bakken, J. Glaum, M. A. Einarsrud, and T. Grande
Enhanced in-plane ferroelectricity in BaTiO₃ thin films fabricated by aqueous chemical solution deposition
AIP Advances 8 (2018) 105228

M. M. Adnan, A. R. M. Dalod, M. H. Balci, J. Glaum and M.-A. Einarsrud
In Situ Synthesis of Hybrid Inorganic–Polymer Nanocomposites
Polymers 10 (2018) 1129

K. Inzani, M. Nematollahi, S. M. Selbach, T. Grande, M. L. Waalekalv, T. Brakstad, T. W. Reenaas, M. Kildemo and F. Vullum-Bruer
Tailoring properties of nanostructured MoO_3−x thin films by aqueous solution deposition
Appl. Surf. Sci. 459 (2018) 822-829

S. L. Skjærvø, K. H. Wells, W. Beek, T. Grande and M.-A. Einarsrud
Kinetics of the hydrothermal synthesis of nanosized K_xNa_1-xNbO₃
CrystEngComm (2018)

S. L. Skjærvø, K. Høydalsvik, A. B. Blichfeld, M.-A. Einarsrud and T. Grande
Thermal evolution of the crystal structure and phase transitions of KNbO₃
.R. Soc. open sci. 5 (2018) 180368.

O. G. Grendal, A. B. Blichfeld, S. L. Skjærvø, W. Beek, S. M. Selbach, T. Grande and M.-A. Einarsrud
Facile Low Temperature Hydrothermal Synthesis of BaTiO₃ Nanoparticles Studied by In Situ X-ray Diffraction
Crystals 8 (2018) 253.

S. L. Skjærvø, K. H. Wells, S. Sommer, T.-D. Vu, J. R. Tolchard, W. Beek, T. Grande , B. B. Iversen and M.-A. Einarsrud.
Rationalization of Hydrothermal Synthesis of NaNbO₃ by Rapid in Situ Time-Resolved Synchrotron X-ray Diffraction
Cryst. Growth Des 18 (2018) 770–774.

A. R. M. Dalod, O. G. Grendal, A. B. Blichfeld, V. Furtula, J. Pérez, L. Henriksen, T. Grande and M.-A. Einarsrud
Structure and Optical Properties of Titania-PDMS Hybrid Nanocomposites Prepared by In Situ Non-Aqueous Synthesis
Nanomaterials 7 (2017) 460.

A. R. M. Dalod, O. G Grendal, S. L. Skjærvø, K. Inzani, S. M. Selbach, L. Henriksen, W. van Beek, T. Grande, and Mari-Ann Einarsrud
Controlling Oriented Attachment and In Situ Functionalization of TiO2 Nanoparticles During Hydrothermal Synthesis with APTES
J. Phys. Chem. C 121 (2017) 11897–11906.

S. L. Skjærvø, S. Sommer, P. Nørby, E. D. Bøjesen, T. Grande, B. B. Iversen and M-A. Einarsrud
Formation mechanism and Growth of MNbO₃, M=K, Na by in situ X-ray diffraction
J. Am. Ceram. Soc. 100 (2017) 3835-3842.

M. Christensen, M.-A. Einarsrud and T. Grande
Fabrication of Lead-Free Bi0.5Na0.5TiO3 Thin Films by Aqueous Chemical Solution Deposition
Materials 10 (2017) 213.

A. Dalod, L. Henriksen, T. Grande and M.-A. Einarsrud
Functionalized TiO2 nanoparticles by single-step hydrothermal synthesis: the role of the silane coupling agents 
Beilstein J. Nanotechnol. 8 (2017) 304-312.

T.O. Løveng Sunde, T. Grande and M.-A. Einarsrud
Modified Pechini Synthesis of Oxide Powders and Thin Films
Handbook of Sol-Gel Science and Technology, Springer, (2016) 1-30.