JSI - Synthesis of Materials K8

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Contact info


Head of Department 

Prof. Dr. Darko Makovec
Telephone: +386 1 477 35 79




Bernarda An┼żelak
Telephone: +386 1 477 33 23

Semiconducting materials


Research on semiconducting oxide materials has a long tradition. Ceramic materials that show grain-boundary phenomena, such as ZnO varistors and positive temperature coefficient resistors (PTCR, posistor) based on donor-doped barium titanate are at the core of semiconducting materials research. The electrical current passing through such materials is determined by voltage (varistor) or temperature (PTCR) dependent potential barriers developed at the grain boundaries of the semiconducting ceramics.


Most of the research was done on PTC resistors. A large jump in the electrical resistance, from the semiconductor to the isolator state, is observed in ferroelectric BaTiO3 ceramics due to the ferroelectric/paraelectric phase transition (at the Curie temperature). The Curie temperature of BaTiO3 can be modified by the substitution of Ba with isovalent ions. Unfortunately, the only ion that increases the Curie temperature of BaTiO3 above its value of 128 oC, is lead, which is toxic. Therefore, a lot of attention is being devoted to the development of a resistor that can operate at elevated temperatures based on high-Curie-temperature lead-free ferroelectrics, such as the ceramics in the KNbO3-BaTiO3, SrNb2O6BaNb2O6 and BaTiO3-Na0.5Ba0.5TiO3 systems


PTCR effect measured in donor-doped BaTO3 ceramics.

JSI - Synthesis of Materials K8