Sintering and ionic conduction of neodymium-bearing fluorobritholites

• Published in: Materials chemistry and physics Vol. 228; pp. 254 - 262
• Main Author: Hidouri, Mustapha
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-04-2019
• Subjects: Ionic conductivity; Lanthanum-neodymium substitution; Sintering; Strontium fluorobritholites; Lanthanum-neodymium substitution; Strontium fluorobritholites; Sintering; Ionic conductivity
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2019.02.050

The present work describes the sintering and ionic conductivity of rare-earth-based fluorobritholite (Sr8La2-xNdx(PO4)4(SiO4)2F2 with 0 ≤ x ≤ 2). The materials were prepared via conventional solid state reactions. The analysis and characterization of the synthesized powders were carried out using several techniques. The samples’ ionic conductivity σ was measured via a complex impedance spectroscopy. The results showed that the substitution of lanthanum and/or neodymium by strontium and silicates by phosphorus in fluorapatite has been established and well-crystallized single-phase apatites were consequently obtained as a result. The neodymium-lanthanum substitution was total according to the small dimensional differences between the two cations. Next, the powders were after that compacted into pellets and then pressurelessly sintered at a 1250–1450 °C temperature range. The relative densities of the sintered bodies were found to depend on sintering temperature as well as on Nd content. The 90% relative density was obtained with x = 2 sample sintered at 1250 °C. The microstructures of the densest bodies were characterized by a closed porosity. The measured ionic conductivity σ of the samples was found to depend simultaneously on both the Nd content and the heating temperatures, while the maximum value of 2.73 10−6 S cm−1 was obtained at 780 °C for x = 2. A correlation between material structures and densification ratios with the ionic conductivity σ was detailed.
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•Fluorobritholites prepared via solid state reaction leaded to single apatite phases.•LaNd substitution was total and induced lattice and crystal size reduction.•Sintered specimens give rise to 90% relative density with grains coalescence.•The ionic conductivity σ = 2.73 10−6 S cm−1 was obtained at 780 °C for x = 2.•The conductivity depends on both Nd content and heating temperature.