Sol-Gel Synthesis, Thermal Behavior of Nanopowders and Chemical Stability of La1-xHoxPO4 Ceramic Matrices

摘要

Nanosized powders of orthophosphates in the LaPO4-HoPO4-H2O system have been synthesized to determine the mutual solubility of LaPO4 center dot nH(2)O and HoPO4 center dot nH(2)O 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 center dot nH(2)O-based solid solutions was observed within the 0 = x = 0.6 concentration range up to 600 degrees C. Further they transformed to monoclinic LaPO4-based form within the 0 = x = 0.3 concentration range. Solubility of LaPO4 center dot nH(2)O and LaPO4 in tetragonal HoPO4(center dot nH(2)O) is lower (= 10 mol %). Specific surface area of La1-xHoxPO4 center dot nH(2)O powders was in the range of 90.5-165.0 m(2)/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/(cm(2) day) for both ions.