Surface electrical properties of Gd-doped PbZrO3

Work function (WF) of undoped and Gd-doped PbZrO₃ (PZG) was determined during isothermal oxidation and reduction experiments at 400 and 500 °C in the P(O₂) range between 10 and 2.1×10⁴ Pa. The obtained results are discussed in terms of two competitive effects, such as (i) an acceptor-type effect due to oxygen chemisorption and its subsequent incorporation into the oxide lattice and (ii) donor-type effect due to p(O₂)-induced structural transitions, such as decomposition of PbZrO₃ resulting in the formation of a surface layer composed of PbO and ZrO₂. Both effects have different rates of appearence and the effect on electrical potential. It was found that oxidation results in irreproducible changes of surface properties involving the formation of a low-dimensional surface layer.     

RKKY interaction in metallic overlayers of fractional dimensionality

Within an analytical approach we study the RKKY interaction mediated by the electron gas, which shows fractional spectral dimensionality. We derive formula for the RKKY exchange integral in a system of nonintegral dimensionality. Also the modifications of magnetic interaction and magnetic moments in metallic overlayers due to the surface/interface effects are considered. Presented at the VIII-th Symposium on Surface Physics, Třešt’ Castle, Czech Republic, June 28 – July 2, 1999.     

Radon in well waters in the Kraków area

The method and the results of radon concentration measurements in water samples are presented. Since May 2000, measurements of radon concentration in well waters in the Kraków area have been carried out--both in urban wells (depth above 50 meters) and in other private wells (depth of several meters). The ionisation chamber AlphaGUARD PQ 2000PRO along with the additional special equipment AquaKIT were used for determination of radon concentration in water samples. A total of 45 wells were examined for radon concentration in water--19 urban wells, 21 private ones (from Nowa Huta, Ojcowska, Wola Justowska area--parts of Kraków) and 5 mineral water sources. Wola Justowska is a region where tectonics faults occur and radon can easily migrate from deep basement structure. All the obtained values of radon concentration are below 12 Bq/l. These preliminary results do not show a direct correlation between geological structure and radon concentration in water samples. However, further investigation is needed and is planned to be undertaken.     

Chemical diffusion in calcium titanate

This work reports the gas/solid equilibration kinetics for the O₂/CaTiO₃ system. The electrical conductivity measurement was applied for monitoring the kinetics in the ranges of temperature 973-1323 K and oxygen partial pressure 10 Pa-72 kPa. It was found that the gas/solid equilibration kinetics for the polycrystalline CaTiO₃ specimen in the above experimental conditions is determined by bulk diffusion rather than by grain boundary conditions. The obtained data of the electrical conductivity vs. time were used for the determination of the chemical diffusion coefficient as a function of temperature at low and high p(O₂), respectively:

(1)     

Effective dimensionality approach to the RKKY interaction in multilayer systems

We consider RKKY interaction in a quasi 2D system with nonparabolic dispersion. In our paper we calculate the RKKY range function assuming the in-layer confinement via effective dimensionality approach. We show, that indirect magnetic exchange in our system can be modelled by the effective spectral dimension which equals one.