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  • A method of manufacturing ferroelectric ceramic based on lithium metaniobate

    The manuscript presents results of a study ferroelectric ceramic metaniobate lithium (PCR-61) which containing Li2O, Nb2O5 and CaO in the fallowing ratio, mass. % Li2O 10,03-10,10; Nb2O5 89,22-89,87; CaO 0,03-0,75. The most effective was the offset component in alcohol and air environments, which providing sufficiently high rate of sintering, the formation on their base high density ceramic with the most perfect crystal structure and microstructure of the equilibrium. Using the foregoing results the solid phase material was prepared by one-stage synthesis (SPS) for Tsint.1 = 820℃, τ = 5h. with followed by sintering by conventional ceramic technology (CCT) (without pressure) at a temperature Ts. = 1150℃, τ = 2h. After machining, the samples were polarized ("oil" polarization). The promising method SPS + CCT was presented. Material based on piezoelectric ceramics metaniobate lithium (PCR 61) was obtained by the SPS + CCT, close to the parameters of hot-pressed (HP) samples and can be used in electrical devices under the influence of ultra-high temperatures. The effectiveness of heterovalent modification as a method of directional changes in the properties of lithium metaniobate was shown.

    Keywords: ferroelectric ceramics, metaniobates lithium, solid-phase synthesis, conventional ceramic technology, the electrical properties, high temperature technology

  • Dielectric spectroscopy of ceramic solid solutions based on modified lead titanate

    The manuscript traced the impact of changes in the content of alkaline-earth elements on the dielectric spectra of solid solutions based on lead titanate. Two concentration areas with sharply differing nature of the manifestations of dispersion phenomena were identified. First (0.02≤α1≤0.24) is characterized by strong dispersion ε/ε0 in all temperature range and not allow to generate maximum of ε/ε0 for Curie temperature at low frequencies, the second (0.24≤α1≤0.36) - a sharp decrease of Δε in the ferroelectric phase and complete disappearance of it in the solid solutions, SS, with α1 = 0.36, indicating stabilization of the structure with the introduction of alkaline SS elements. It was found that as increased the concentration of modifiers in the compositions there is a stabilization of their structure with a gradual decrease in the phase transition temperature. Formation of two concentration areas where changes macro properties SS is undoubtedly a consequence of their correlation with the phase diagram of the studied SS, which is experiencing a transformation in the neighborhood of α1 ~ 0.24, due to the transition from two-phase to single-phase state. The results obtained by the authors can be used in the development of high-temperature (α1 0.24 ) anisotropic ferroelectric materials.

    Keywords: ferroelectric piezoceramics, lead titanate, alkaline earth elements, modifiers, solid phase synthesis dielectric spectra

  • Thermodynamic background and the effects of the degradation of the modified lead titanate

    The paper provides information on the influence of thermodynamic prehistory (conditions for obtaining) and the processes associated with time "aging" of the samples in the dielectric properties of the alkaline-earth elements modified lead titanate ceramics. The data shows a dielectric stability of solid solutions (SS) with a high content of alkaline-earth elements (almost independently of the Curie temperature of sintering temperature). This is supported by the fact of reproduction the character of dielectric spectra in SS (α1≥0.22) unlike changed profile curves ε / ε0 (T) |f SS (α1 = 0.04). The splitting of the maxima ε / ε0 (T) |f, obtained on the same samples after 7 months (April 2015) after the initial measurements (September 2014) is the result of degradation of solid solutions close to PbTiO3, probably due to begin the process of self-destruction ceramics.

    Keywords: ferroelectric ceramics, lead titanate, alkaline-earth elements, thermodynamic prehistory, dielectric properties, the effects of degradation