Recrystallization of niobate piezoelectric ceramics in the presence of liquid phase

Piezoelectric ceramics of LiNbO₃ and LiNbO₃-based solid solutions have been sintered from raw materials with different fluorine concentrations. The peculiarities of the structure formation and doping effect on the grain structure are studied. Multifractal parameterization of the ceramics grain structure is per-formed. The possibility of preventing the development of destructive recrystallization in niobate piezoelectric ceramics is shown.     

Two phase diagrams of Pb(Ti0.485Zr0.515)0.98(Nb0.5Bi0.5)0.02O3 solid solution in the temperature range 20 ≤ t ≤ 600°C

A high-temperature analysis of Pb(Ti_0.485Zr_0.515)_0.98(Nb_0.5Bi_0.5)_0.02O₃ solid solution has been carried out in the temperature range 20 ≤ t ≤ 600°C by X-ray powder diffraction. Two different phase diagrams are plotted: one is based on the change in the diffraction pattern of main reflections, while the other is based on the diffraction pattern of real (defect) structure. A transition to the cubic phase can be observed at t ≥ 360°C (in the former diagram) and t ≥ 450°C (in the latter diagram). The nonmonotonic (with inflection points) behavior of the temperature dependence of the cell volume in the cubic phase is explained.     

Reversible and piezoelectric nonlinearity: The dielectric response in multicomponent solid solutions with different manifestations of the character of ferroelectric properties

Ceramics of a modified Ba multicomponent system of PbNb_2/3Zn_1/3O₃-PbNb_2/3Mg_1/3O₃-PbNb_2/3Ni_1/3O₃-PbTiO₃ were developed. A comprehensive study was peformed of the reversible dielectric nonlinearity and electromechanical, dielectric, and piezoelectric characteristics of the multicomponent ceramics, which have properties of relaxors, ferroelectric materials with diffused phase transitions, and classical ferroelectric material. Correlations between compounds, structures, properties, and ranges of application were established.     

Poly(3-Hydroxybutyrate) Matrices Modified with Iron(III) Complexes with Tetraphenylporphyrin. Analysis of the Structural Dynamic Parameters

The effect of small additions of the iron(III) complex with tetraphenylporphyrin (0–5%) on the structure and properties of ultrathin fibers based on poly(3-hydroxybutyrate) (PHB) was studied by differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), EPR probe method, and scanning electron microscopy. When tetramethylporphyrin was added to the PHB fibers, the crystallinity significantly increased, and the molecular mobility in the amorphous regions of the polymer decreased. The thermal treatment of the fibers (annealing at 140°C) led to significantly increased crystallinity and decreased molecular mobility in the amorphous regions of the PHB fibers. The addition of tetramethylporphyrin to the PHB fibers led to a sharp decrease in crystallinity. Ozonolysis of the fibers at small treatment times caused a considerable decrease in their molecular mobility (to 5 h), while prolonged ozonolysis led to increased mobility. The obtained fibrous materials have bactericidal properties and will find use in the development of antibacterial and antitumor therapeutic systems.