
Tuomo SiponkoskiUniversity of Oulu · Faculty of Information Technology and Electrical Engineering
Tuomo Siponkoski
Doctor of Science in Technology
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26
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Introduction
Additional affiliations
September 2012 - present
June 2009 - December 2011
Publications
Publications (26)
We have used high-pressure synthesis to synthesize samples of Ca 2- x Mn x Ti 2 O 6 double perovskite, where x varies between 0.2 and 1. The synthesized materials were structurally characterized with powder X-ray diffraction (XRD)....
The charge generation properties of solid, UV-cured and charge-separated ionic liquid electrets as energy harvesters.
Information data and persistent link to the Thesis.
This thesis introduces three state-of-the-art piezoelectric composites developed in the work together with their fabrication, properties and future prospects. The investigated materials were printable ceramic-polymer composite Pb(ZrTi)O3-P(VDF-TrFE) and ultra-low temperature fabricated all-ceramic upside-down composites Pb(ZrTi)O3-LiMoO4 and Pb(ZrT...
Organic Conductors Achieving excellent electrical, mechanical, and self‐healing properties with soft conductor has been challenging so far. In article number 2205485, Jarkko Tolvanen and co‐workers report a co‐continuous multiphase design strategy for self‐healable organic conductor‐elastomer blend that achieves a good overall performance. The cove...
Next‐generation, truly soft, and stretchable electronic circuits with material level self‐healing functionality require high‐performance solution‐processable organic conductors capable of autonomously self‐healing without external intervention. A persistent challenge is to achieve required performance level as electrical, mechanical, and self‐heali...
In this work, the electromechanical properties of a lead zirconate titanate-poly(vinylidenefluoride-trifluoroethylene) ceramic-polymer composite on thin brass and steel substrates were investigated. Samples were stencil printed on metal foils and cured at 120 °C. The effective transverse piezoelectric coefficient (d31eff) was calculated by utilizin...
This work presents the next leap in piezoelectric all-ceramic composites fabricated at ultra low temperatures. The “Upside-down” composite method is further developed and instead of the water-soluble lithium molybdate used in our earlier study, an organotitanate based precursor gel is used as a binder. Utilizing heat and pressure the precursor tran...
A method to realize ultra-low temperature co-fireable ceramic composites with ultra-low permittivity is presented in this work. Hollow glass microspheres with a size of 10–100 μm were used as a filler in a tape based on lithium molybdate (Li2MoO4) ceramic to introduce controlled porosity and reduce the relative permittivity of the sintered product....
In this paper a significant advance in the piezoelectric properties of poly(vinylidenefluoride-trifluoroethylene)-lead zirconate titanate (P(VDF-TrFE)-PZT) composite ink has been achieved by coating the ceramic particles prior to formulation with a polymeric surfactant containing carboxylic acid anhydride functional groups and the piezoelectric res...
In this contribution, we evaluate the performance of an additively fabricated piezoelectric poly(vinylidenefluoride-cotrifluoroethylene) (P(VDF-TrFE)) based dynamic pressure sensor in non-invasive arterial pulse wave (PW) measurement. Additively fabricated piezoelectric sensors have high potential for the realization of affordable and unobtrusive P...
Piezoelectric materials have a multi-billion dollar impact on the electromechanical transducers market. Their conventional synthesis includes a sintering step (at over 1000 °C) that often hampers direct integration into monolithic devices and confines their applications to heterostructures made using tedious multi-step assembly or to composites wit...
In this work, all-ceramic barium strontium titanate (BST) composite is fabricated for the first time at room temperature without sintering, showing a clear phase transformation behavior at Curie temperature and excellent electrical properties. The samples fabricated using pre-treated BST particles with a ceramic binder and selection of the overall...
This paper reports the first ultralow sintering temperature (450 oC) co-fired multifunctional ceramic substrate based on a commercial lead zirconium titanate (PZ29)-glass composite and fabricated by tape casting, isostatic lamination, and sintering. This substrate was prepared from a novel tape casting slurry composition suitable for co-firing at t...
The α-MoO3 ceramics were prepared by uniaxial pressing and sintering of MoO3 powder at 650°C and their structure, microstructure, densification and sintering and microwave dielectric properties were investigated. The sintering temperature of α-MoO3 was optimized based on the best densification and microwave dielectric properties. After sintering at...
A perovskite solid-solution, (1-x)KNbO3-xBaNi1/2Nb1/2O3-δ (KBNNO), has been found to exhibit tunable bandgaps in the visible light energy range, making it suitable for light absorption and conversion applications, e.g., solar energy harvesting and light sensing. Such a common ABO3-type perovskite structure, most widely used for ferroelectrics and p...
A new glass free low temperature sinterable CuMoO4 ceramic was prepared by solid state ceramic route. The structural, microstructural, electron dispersive spectrum and X-ray photoelectron spectroscopy analysis revealed the quality of the material synthesized. The CuMoO4 ceramic sintered at 650 oC exhibits densification of 96 % and low coefficient o...
A new glass with ultra-low glass transition temperature based on 10Li2O-10Na2O-20K2O-60MoO3 (LNKM) has been devel-oped by conventional glass melting and quenching process. The glass has ultra-low glass transition and melting temperatures being 198 oC and 350 oC respectively. The glass exhibits a coefficient of thermal expansion of 17 ppm/oC in the...
Self-standing films (45-μm thick) of native cellulose nanofibrils (CNF) were synthesized and characterized for their piezoelectric response. The surface and the microstructure of the films were evaluated with image-based analysis and scanning electron microscopy (SEM). The measured dielectric properties of the films at 1 kHz and 9.97 GHz indicated...
The fabrication and electromechanical properties of composite inks consisting of 30 to 70 vol.% of piezoceramic PZT powder and piezoelectric co-polymer P(VDF-TrFE) are presented. Samples were stencil-printed on a commercial PET film and printable silver ink was used for the electrodes thus allowing a maximum process temperature of 130 °C. The relat...
In this research a composite for printable capacitors using screen printed structures and low temperature curing ferroelectric ink was investigated. The realized ink consisted of 40 vol% barium titanate in a poly(vinylidenefluoride-trifluoroethylene) matrix. DuPont silver ink 5064H was used for the conductive lines in the design and the maximum pro...