Projects / Programmes source: ARIS

Odvisnost funkcijskih lastnosti tankih plasti na osnovi okolju prijaznih perovskitov od mikrostrukture in kemijskih homogenosti (Slovene)

Research activity

Code Science Field Subfield
2.09.00  Engineering sciences and technologies  Electronic components and technologies   
Evaluation (rules)
source: COBISS
Researchers (13)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  19038  PhD Andreja Benčan Golob  Materials science and technology  Researcher  2008 - 2011 
2.  29158  PhD Elena Chernyshova  Physics  Researcher  2008 - 2011 
3.  05214  Jena Cilenšek    Technical associate  2008 - 2009 
4.  06423  PhD Janez Holc  Materials science and technology  Researcher  2008 - 2011 
5.  02627  PhD Marija Kosec  Electronic components and technologies  Researcher  2008 - 2011 
6.  31064  PhD Alja Kupec  Mechanical design  Junior researcher  2009 - 2011 
7.  02572  Srečo Maček    Technical associate  2010 - 2011 
8.  04587  PhD Barbara Malič  Electronic components and technologies  Head  2008 - 2011 
9.  29877  Branka Perc  Textile and leather  Researcher  2009 - 2011 
10.  27820  Tina Ručigaj Korošec    Technical associate  2008 - 2011 
11.  26547  PhD Gaj Stavber  Chemistry  Researcher  2010 - 2011 
12.  28808  PhD J.J. Angeline Tellier  Materials science and technology  Researcher  2008 - 2011 
13.  29745  PhD Gregor Trefalt  Electronic components and technologies  Junior researcher  2008 - 2011 
Organisations (1)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  18 
Significance for science
Alkali niobates, niobate tantalates and/or their solid solutions with alkali-earth titanates form a group of ceramic materials which could replace lead-based complex perovskites with excellent di-, ferro- or piezoelectric properties. The latter contain more than 60 wt. % lead oxide and they represent an environmental hazard. Materials, which are at working temperatures in paraelectric phase, such as potassium tantalate niobates, exhibit high capacitance tunability with applied electric field and are interesting for wireless communications. Miniaturization and integration of electronic components are the drivers for the research of thin films. The processing of thin films based on alkali niobates or niobate tantalates is demanding due to hygroscopicity of the reagents and a high vapor pressure of alkali species at processing temperatures which consequently results in a low number of publications. There is no data on the mechanism of nucleation in alkali niobate based films from solutions and consequently also not on the evolution of microstructure. Our research is oriented towards study of nucleation, evolution of microstructure and texture of thin films based on (K0.5Na0.5)NbO3 , KTa0.6Nb0.4O3 in CaCu3Ti4O12and their influence on functional properties. Within the research of (K0.5Na0.5)NbO3 thin films on Pt(111)/TiO2/SiO2/Si substrates we focused on the influence of the amount and chemical composition of the alkali excess in coating solutions on crystallization and microstructure evolution. Upon rapid thermal annealing at 750 °C the films crystallized in pure perovskite monoclinic phase with a {100} preferential orientation. The amount of alkali excess in the precursor solutions, 5 or 10 mole %, influenced the nucleation and growth processes, resulting in the films with granular equiaxed microstructures or columnar microstructures, respectively. The energy-dispersive X-ray spectroscopy in field-emission scanning electron microscope revealed that volatilization of potassium oxide was more pronounced than volatilization of sodium oxide. The films prepared from the solution with 5 mole % potassium excess had the composition which was the closest to the nominal KNN composition among all samples and exhibited the best dielectric and ferroelectric properties among the studied films. Dielectric measurements of KTa0.6Nb0.4O3 thin films on alumina substrates, prepared by CSD from acetate-alkoxide based sols with 24-h reflux were performed in radio frequency range by patterning planar capacitors on the film surface and in microwave frequency range by split-post dielectric resonator method. The relaxorlike behavior of dielectric properties, which has not been determined in K(Ta,Nb)O3 thin films previously, was unambiguously confirmed by the fit to the Vogel–Fulcher law. The CaCu3Ti4O12 thin films were prepared from the nitrate-alkoxide based solutions. The films, prepared by rapid annealing at 750 oC of the as-deposited layers consisted of equiaxed grains of a few 10 nm. By introducing a nucleation layer, the microstructure with columnar grains of a few 100 nm across was obtained. The RT value of dielectric permittivity of the granular films was about 1100 at 1 kHz, more than five times larger than that of the columnar films. The temperature dependence of dielectric permittivity of the films could be tailored by post-annealing in different atmospheres.
Significance for the country
Research of lead-free piezoelectric materials is important for Slovenia and for the EU, which is a consequence of the increased awareness of the society in regard of protection of environment and health and also of the legislation within the EU, namely Restriction of Hazardous Substances Directive (RoHS, 2002/95/EC) and Waste Electrical and Electronic Equipment Directive – (WEE, 2002/96/EC). The research of thin films based on sodium potassium niobate focused on the correlation of microstructure, chemical homogeneity and orientation of the perovskite phase and functional properties of thin films. In calcium copper titanante thin films the relation between the microstructure and the frequency dependent dielectric permittivity was established. The research of potassium tantalate niobate films included dielectric properties from radio frequency to microwave range with a possibility of application as active elements in microwave antennas. Members of the research team have been active in Slovenian Centres of Excellence SPACE: Science and technology (coordinator: Prof. Tomaž Rodič), NANOCENTER (coordinator: Prof. Dragan Mihailović) and NAMASTE: Advanced Materials and Technologies for the Future (coordinator: Prof. Marija Kosec). The knowledge and expertise gained within the project has contributed also to research aims of the three centres. For example, the research on thin film voltage tunable capacitors based on potassium tantalate niobate as phase shifters in microwave antennas has taken place also within the Centre of Excellence SPACE, Workpackage Satellite communications, hybrid antennas and radar together with the Laboratory for radiation and optics, Faculty for Electronics, University of Ljubljana. The company Iskra TELA, producer of antennas, is also a partner. The research is important also for possible collaboration in the projects of the European Space Agency.
Most important scientific results Annual report 2008, 2009, final report, complete report on dLib.si
Most important socioeconomically and culturally relevant results Annual report 2008, 2009, final report, complete report on dLib.si
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