Synthesis and Properties of Phases in the PbO–MO–Nb₂O₅ (M = Cu, Ni) Systems

In this paper, we report the solid-state synthesis, characterization, and physicochemical properties of Pb_4–xM_xNb₂O₉ (M = Cu, Ni; x = 0–1.0) solid solutions. We have identified the stability limits of the solid solutions. Using the tolerance factor and relative electronegativities of the A- and B-site atoms (A₄B₂O₉), we have identified the stability fields of the perovskite-related solid solutions. The materials have been characterized by X-ray diffraction, and the particle size composition of the synthesized powders has been determined. Their electrical conductivity has been measured as a function of temperature. We have studied the key electrochemical characteristics of solid-contact ion-selective electrodes fabricated using the synthesized materials: linear range and slope of the principal electrode function, working pH range, and response time.