Compact ceramic samples of lead zirconate–titanate are sintered from nanocrystalline (d av = = 25 nm) Pb(Zr0.52Ti0.48)O3 powder synthesized by thermal decomposition of an oxalate precursor. Conditions of nanopowder compaction have been found and kinetics of sintering and growth of nanocrystallites and coarser grains formed during consolidation have been studied. The lead zirconate–titanate ceramic samples consolidated from nanopowders are sintered at lower (by 300–350°C) temperatures and have higher (by 25–45%) dielectric and piezoelectric properties as compared to samples fabricated by conventional solid-state technology. Two-level grain structure is formed during sintering: nanocrystallites divided by low-angle boundaries and descending from initial nanocrystalline particles and consolidated coarser micrograins divided by high-angle boundaries. Sintering of the lead zirconate–titanate ceramics from nanocrystalline powders permits controlling the nanoscale size of crystallites and thus the nanostructured features of consolidated material.

Complex oxides with the perovskite structure demonstrate an ability to considerable deviations of their composition from stoichiometry. The nonstoichiometry regions of oxides of the perovskite family, dependence of nonstoichiometry from the synthesis conditions and the characteristics of point defect formation in alkaline-earth metatitanates are considered in this paper. The quantitative models of point disorder have been constructed. The models predict the values of nonstoichiometry, the defect concentrations and the properties of perovskites for given conditions of their synthesis.

The possibility of quantitative CuO reduction to Cu2O and of oxygen stoichiometry control in YBa2Cu3O x in the nonaqueous medium CH3OH-TiCl4-Al at room temperature is demonstrated, and the conditions required for these processes are reported. In this reduction system (with Al as the electron donor), which affords a marked decrease in the reaction temperature, solvated TiCl4 ions transfer electrons to the oxide surface and CH3OH provides ligands for titanium chloro complexes. The rate-limiting step of the reaction is diffusion through the product layer. The diffusion coefficients determining the rate of the reaction are estimated to be D = (1.8 ± 0.5) × 10−2 × exp[−(91.5 ± 3.0)/RT] m2/s for CuO reduction and D = (8.1 ± 3.6) × 10−14 × exp[−(23.6 ± 2.5)/RT] m2/s for YBa2Cu3O6.96 reduction (the activation energies are in kJ/mol). A comparison of these diffusion coefficients with experimental data suggests that the rate of the reaction is determined by copper ion transfer through the Cu2O layer via rapid diffusion pathways and by oxygen transfer in the basal planes (001) of the YBa2Cu3O x crystallites.

The existing data on the mechanism of peritectic decomposition of the metal oxide YBa2Cu3O x are ambiguous. This process cannot be studied without quite sensitive methods of phase analysis and allowance for its dependence on the partial pressure of oxygenp(O2) in the gas phase. The methods of x-ray diffractometry, scanning electron microscopy, and local electron-probe and thermal analyses are used to study the transformations in heating YBa2Cu3O x above 900°C in air and in vacuum at a residual pressurep(O2)=700 Pa.

The methods of scanning electron microscopy, local electron probe analysis, and x-ray diffraction analysis are used for studying the morphology and local composition of grains in melt-textured long specimens of superconductors based of barium-yttrium cuprate and fabricated by the method of zone melting.

The microstructure, preferred orientation, and axial inhomogeneities of composition and critical currents in melt-textured YBCO samples in the shape of bars were studied. The microstructure of the material is dominated by large platelike grains. Most of these grains consist of YBa2Cu3Ox (123 phase); large grains of Y2BaCuO5 (211 phase) and a 123/211 intergrowth phase are also present. In addition, the material contains small, randomly oriented grains of Y2BaCuO5, YBa2Cu3Ox, and BaCuO2. A wide scatter in 211 content and oxygen stoichiometry of 123 along the bar samples is revealed. The variations in phase composition are found to be strongly correlated with those in critical current.

The oxygen content and its influence (during subsequent cooling) on the superconducting properties of the metaloxide ceramic YBa2Cu3Ox are measured at temperatures (T) 300−1000 °C under partial pressures (pO2) 10−105 Pa. The position of the oxygen isoconcentrates for 6.2 < x < 7 is determined from the pO2-T diagram by gravimetric method with absolute calibration by reduction to metallic copper. It is shown that the oxygen in the compound exists in the strongly bound form (6 g-atom/mol.) and in a weakly bound form which is responsible for superconductivity. The amount δ of weakly bound oxygen is determined by quenching the samples in liquid hydrogen. The nature of correlation of δ with the critical temperature Tc and the diamagnetic response LYBCO is reconstructed. It is found that the shape of the LYBCO(δ) and Tc (δ) is in accord with the formation of stoichiometric ionic crystals with Cul+ , Cu2+, and Cu3+ ions in the basal plane of the compound for δ = 0, 0.5, and 1, respectively. It is established that for x < 6.5, the metaloxide ceramic YBa2Cu3Ox exists in a tetragonal superconducting phase.

The authors study the effect of annealing conditions in different gaseous media on the properties of piezoceramic materials based on lead zirconate-titanate. The experimental curves of the activity and vapor pressure of PbO versus the lead-oxide content in LZT at 1370 degrees K are shown. Changes in the equilibrium vapor pressure of PbO during heat treatment cause significant deviations from stoichemetry and strongly affect the dielectric and piezoelectric properties of piezoceramic based on lead titanate-zirconate.