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Abstract

Mixture of nickel and titanium powders were milled in planetary mill under argon atmosphere for 100 hours at room temperature. Every 10 hours the structure, morphology and chemical composition was studied by X-ray diffraction method (XRD), scanning electron microscope (SEM) as well as electron transmission microscope (TEM). Analysis revealed that elongation of milling time caused alloying of the elements. After 100 hours of milling the powders was in nanocrystalline and an amorphous state. Also extending of milling time affected the crystal size and microstrains of the alloying elements as well as the newly formed alloy. Crystallization of amorphous alloys proceeds above 600°C. In consequence, the alloy (at room temperature) consisted of mixture of the B2 parent phase and a small amount of the B19' martensite. Dependently on the milling time and followed crystallization the NiTi alloy can be received in a form of the powder with average crystallite size from 1,5 up to 4 nm.
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Abstract

The discovery of (BaxCa1-x)(ZryTi1-x)O3 lead-free ceramics drawn a lot of attention to those novel materials because of their excellent piezoelectric properties. However, quite a little attention has been paid to other features of the material. This article reports a wide range of research, including composition, structure and microstructure, dielectric response and impedance spectroscopy in order to systematize and expand knowledge about this peculiar ceramics and strontium doping effect on its properties. In order to test that influence a series of samples with various strontium concentration, precisely the admixtures of 0.02, 0.04 and 0.06 mol% were prepared, as well as basic ceramics to compare obtained results.
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Abstract

In the work five ceramic compounds based on the (K0.44Na0.52Li0.04)NbO3 (KNLN) material modified with oxides: Cr2O3, ZnO, Sb2O3 or Fe2O3 (in an amount of 0.5 mol.%) were obtained. The KNLN-type composition powder was prepared by solid phase synthesis from a mixture of simple oxides and carbonates, while compacted of the ceramic samples was conducted by free sintering methods. In the work the effect of the used admixture on the electrophysical properties of the KNLN ceramics was presented. The XRD, EDS tests, the SEM measurements of the morphology ceramic samples, dielectric properties and DC electric conductivity were conducted. The research showed that the used admixtures introduced into the base of KNLN-type composition improve the microstructure of the ceramic samples and improve their sinterability. In the case of the dielectric measurements, it was observed a decrease in the maximum dielectric permittivity at the TC for dopred KNLN-type samples. The addition of an admixture of chromium, zinc, antimony or iron in an amount of 0.5 mol.% to the base composition (K0.44Na0.52Li0.04)NbO3 practically does not change the phase transition temperature. The diminution in the density value of doped KNLN ceramics was attributed to the alkali elements volatilization.
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