The properties of multiferroic BiFeO3 nanoparticles with core-shell structure produced by mechanically activated room temperature synthesis were studies by electron spin resonance spectroscopy and X-ray diffraction. The data reveal essential differences in ordered and disordered regions among as-prepared and annealed samples. The thermally-induced increase in the average size of the grains and disappearance of the disordered grain shell determined from the electron spin resonance and X-ray diffraction are in a good agreement and were confirmed by transmission electron microscopy observations. Ferro- and ferrimagnetic ordering was observed in as-prepared BiFeO3 nanograins, whereas antiferromagnetic order was apparent in the annealed material. The results show that the electron spin resonance spectroscopy can be considered as an useful method to determine the type of magnetic ordering in multiferroic nanoparticles.

Abstract. In the paper the influence of mechanical activation of the powder on the final dielectric properties lead-free Ba(Fe 1/2 Nb 1/2 )O3 (BFN) ceramic was examined. The BFN ceramics were obtained by 3-steps route. Firstly, the substrates were pre-homogenized in a planetary ball mill. Than, the powder was activated in vibratory mill (the shaker type SPEX 8000 Mixer Mill) for different duration between 25 h and 100 h. The influence of the milling time on the BFN powder was monitored by X-ray diffraction. The diffraction data confirmed that the milling process of the starting components is accompanied by partial synthesis of the BFN materials. The longer of the high-energy milling duration the powders results in increasing the amount of amorphous/nanocrystalline content. The mechanically activated materials were sintered in order to obtain the ceramic samples. During this temperature treatment the final crystallisation of the powder appeared what was confirmed by XRD studies. The performed dielectric measurements have revealed the reduction of the dielectric loss of the BFN ceramics compared to materials obtained by classic methods.

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In the paper, the multicomponent PZT-type ceramics with Pb(Zr0.49Ti0.51)0.94Mn0.015Sb0.01W0.015Ni0.03O3 composition have been obtained by conventional and mechanochemical methods. With conventional ceramic technology, PZT-type ceramics have been synthesized by the method of calcination powder (850 °C/4 h). Instead of this step, the mechanochemical synthesis process for different milling periods (15 h, 25 h, 50 h, 75 h) has been applied for a second batch of samples. To obtain the dense PZT-type ceramic samples, powders have been sintered by free sintering method at conditions of 1150 °C/2 h. Studies have shown that the perovskite structure of the PZT-type material is formed during mechanochemical activation of powders during the technological process at low temperature. The application of the mechanochemical synthesis to obtain the PZT-type materials also allows shortening of the technological process, and the useful electrophysical properties of ceramic samples are not reduced at the same time. The presented results have confirmed that the investigated materials can be used in microelectronic applications, especially as elements of actuators and piezoelectric transducers.

Lead titanate nanopowders were fabricated by mechanochemical synthesis from lead oxide and titanium dioxide. The milling process has been carefully investigated by X-ray diffraction and X-ray excited photoelectron spectroscopy. The first traces of perovskite phase were detected after 5 h synthesis. It was found that intermediated phases (Ti 10 O 18 and Pb 3 O 4 ) have been formed at the early stage of synthesis. The 50 h milling results in single perovskite phase with average crystallite size of 20 nm.