Synthesis of Nano-Sized Solid Electrolyte Pr\(_{{1-y}}\)SryF\(_{{3-y}}\) and the Effect of Heat Treatment on the Ionic Conductivity of Fluoride Nanoceramics

Solid electrolyte nanoceramics Pr\(_{{1-y}}\)Sr_yF\(_{{3-y}}\) (y = 0.03, sp. gr. \(P\bar {3}c1\)) were obtained by high-energy milling of melt-grown crystals, followed by cold pressing. The phase composition, microstructure, morphology, and electrical properties of nanoceramics were studied using X-ray diffraction analysis, electron microscopy, and impedance spectroscopy. The room-temperature conductivity of the synthesized Pr_0.97Sr_0.03F_2.97 nanoceramics (σ_cer = 1.7 × 10⁻⁷ S/cm) is much lower than the conductivity of the original single crystal (σ_crys = 4.0 × 10⁻⁴ S/cm), which is due to its low (~75% of the theoretical value) density. Heat treatment of nanoceramics at 823 K in vacuum leads to a threefold increase in σ_cer, and annealing at 1273 K in a fluorinating atmosphere results in further increase in conductivity (σ_cer = 4.3 × 10⁻⁵ S/cm) due to the collective recrystallization and significant increase in the ceramics density (up to 90%). The mechanical milling and subsequent heat treatment of Pr\(_{{1-y}}\)Sr_yF\(_{{3-y}}\) nanopowder make it possible to process single-phase highly conductive ceramics. The proposed method for the synthesis of ceramic fluoride nanomaterials as a technological form of solid electrolytes is a promising way for further developments in the field of creating fluorine-ion current sources and fluorine gas sensors.