Creation of precipitates in bulk matrix to act as pinning centres is a prospective way to improve critical current density in high temperature superconductors. It is possible to generate such precipitates via partial decomposition of the supersaturated solid solution derived from a superconducting phase. To control this process one should go by a knowledge of stability field for these solutions. The objective of present work was determination of the homogeneity area of Bi 2 Sr 2 Ca 1−x R x Cu 2 O 8+d and Bi 2 Sr 2−x CaR x Cu 2 O 8+d (R = Nd, La). Semi-quantitative XRD analysis was used to evaluate phase composition of specimens quenched from various temperatures. It was found that solubility limits of Nd and La in Bi-2212 for cases of alkaline earth element substitution by rare earth elements with smaller ionic radii (substitution Ca by Nd; Sr by Nd and La) were the same (values of x are about 0.8). These limits are determined by fraction of Cu + ions in lattice site attributed to Cu 2+ . In case of substitution of Ca by La stability area of 2212 was found to be much narrower (values of x about 0.3) compared to other substitutions. One ca n deduce this fact from the difference of Ca 2+ and La 3+ ionic radii.

The properties of powder synthesized from calcium acetate and sodium hydrophosphate with the ratio \( \left[ {{\text{C}}{{\text{a}}^{{2 + }}}} \right]/\left[ {{\text{PO}}_4^{3 - }} \right] \) of the starting reagents equal to 1 have been investigated. After synthesis brushite, monetite, and octacalcium phosphate were found in the powder. A substantial mass loss, equal to 26%, on heating is due to not only the decomposition of the phases found but also the removal of the byproducts, consisting of sodium acetate and acetic acid and present in the powder, of the reactions occurring when the solutions of the starting substances interact. After firing at temperatures above 900°C the phases β-Ca2P = O7, β-Ca3(PO4)2,and Ca10Na(PO4)7 are found in the samples.

The properties of Ca-deficient hydroxyapatite powder synthesized from calcium nitrate and ammonium hydrophosphate at 60°C, pH = 7, and Ca/P = 1.67, 1.61, and 1.48 are presented. After sintering at 1100°C for 6 h the phase composition of the ceramic based on these powders was represented by tricalcium phosphate (Ca/P = 1.48) or tricalcium phosphate hydroxyapatite (Ca/P = 1.67 and 1.61). The grain size of the ceramic was 100 – 1000 nm.

MC-40 membrane samples modified with a thin MF-4SC layer containing inorganic oxide particles have been synthesized. Deposition of an MF-4SC layer raises the diffusion permeability of the membrane. Insertion of ZrO 2 or SiO 2 nanoparticles into this layer enhances the ion transport selectivity in terms of the cation transport number. The best results are obtained with oxide particles synthesized in the pores of the deposited layer.

We compare ionic conductivity in zirconium hydrogen phosphate samples with NASICON structure prepared by various methods. Hydrothermal and hydrothermal/ultrasonic treatment reduces the crystallite size and increases ionic conductivity in HZr2(PO4)3 · nH2O samples at low temperatures. At high temperatures, the conductivity of the anhydrous phase HZr2(PO4)3 is higher in the material prepared by ion exchange. Ultrasonication does not considerably improve the properties of hydrothermally prepared samples.

Hydroxyapatite (HA) synthesis by precipitation with urea from aqueous solutions of calcium nitrate and ammonium hydrogenphosphate is studied. Ultrasonication during the synthesis decreases the size of platelet HA crystals from several micrometers to 200–300 nm. At low calcium concentrations in solution, the crystallizing phase is carbonate-hydroxyapatite, whereas at high calcium concentrations, octacalcium phosphate (OCP) precedes hydroxyapatite crystallization.

The thermodynamic parameters of ion exchange have been estimated for HZr 2 (PO 4 ) 3 · H 2 O and the products of its aliovalent doping. Ion exchange occurs via formation of the (H 3 O 1 − x Na x )Zr 2 (PO 4 ) 3 solid-solution series. As in the case of ion exchange on layered zirconium phosphate (Zr(HPO 4 ) 2 · H 2 O), the interdiffusion coefficient and the major interfacial defect generation processes are considerably affected by the contact-solution pH.

The effect of the precipitation pH and subsequent heat treatment is studied on the properties of hydrous zirconium dioxide precipitated by ammonia from nitrate solutions. Precipitation at pH ≤ 6 generates hydrous zirconium dioxide, which contains excess sorbate nitrate ions; the product precipitated at pH ≥ 7 contains excess ammonium ions. This distinction considerably affects the course of thermolysis and the morphology of products. The exotherm associated with the formation of the crystal structure of zirconia becomes more pronounced with rising precipitation pH. In addition, the samples prepared at pH ≥ 7 have a more developed surface. The morphologic and microstructural evolution of hydrous zirconium dioxide samples during thermolysis is described.