New process for the preparation of pigment-coated phosphors on the base of electroacoustic characterization

A simple and easily reproducible method for binding pigment particles to phosphor ones was realised, using an heterocoagulation process. An electrokinetic technique was used to measure the ζ potential of phosphor and pigment particles suspensions at different pH in the presence or not of dispersing and binding agents. Starting from the results of these measurements it was possible to optimise the process. This process introduced as binding agent a liquid fatty amine, generally used as liquid anion exchanger and never used before at this purpose, whilst as dispersing agent it was used an ammonium salt of polyacrilic acid. The pigment powder was coagulated over the phosphor powder in a pH region where surfaces had opposite charge, resulting in a stable deposition of pigment on the phosphor particles.