| 摘要 |
Colloidal dispersions of rare-earth borates include a liquid phase and borate colloids dispersed therein, these colloids having a mean hydrodynamic diameter of at most 200 nm and consisting essentially of elementary particles having a mean size of less than 100 nm; such dispersions are prepared by: (a) reacting a rare-earth oxide with a controlled amount of a water-soluble monovalent acid, having a pKa of from 2.5 to 5.0; (b) heating the medium thus obtained; (c) adding boric acid to the medium obtained and heating the resulting mixture; and (d) separating the solid product from the liquid medium thus obtained, and redispersing same in a liquid phase (the subject borates are useful luminophores, especially for the manufacture of luminescent transparent materials).
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