Sol-Gel Synthesis, Thermal Behavior of Nanopowders and Chemical Stability of La1 – xHoxPO4 Ceramic Matrices
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Nanosized powders of orthophosphates in the LaPO4–HoPO4–H2O system have been synthesized to determine the mutual solubility of LaPO4 · nH2O and HoPO4 · nH2O initial components and to obtain ceramic matrices by sintering them. Formation of hexagonal, monoclinic or tetragonal solid solutions was revealed, and their limits and thermal stability were determined. A series of limited hexagonal LaPO4 · nH2O-based solid solutions was observed within the 0 ≤ x ≤ 0.6 concentration range up to 600°C. Further they transformed to monoclinic LaPO4-based form within the 0 ≤ x ≤ 0.3 concentration range. Solubility of LaPO4 · nH2O and LaPO4 in tetragonal HoPO4(· nH2O) is lower (≤10 mol %). Specific surface area of La1–xHoxPO4 · nH2O powders was in the range of 90.5–165.0 m2/g depending on x. Leaching rate of La3+ and Ho3+ from La1–xHoxPO4 matrices in nitric acid solution (pH 1–2) was determined to be 10–5–10–2 g/(cm2 day) for both ions.
Keywordssol-gel La1 – xHoxPO4 · nH2O nanopowders ceramic matrices thermal and chemical stability
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