Electrophoretic Deposition of Phosphors: I. Conductivity and Zeta Potential Measurements
✍ Scribed by Michael J. Shane; Jan B. Talbot; Ruth D. Schreiber; Colette L. Ross; Esther Sluzky; K.R. Hesse
- Publisher
- Elsevier Science
- Year
- 1994
- Tongue
- English
- Weight
- 449 KB
- Volume
- 165
- Category
- Article
- ISSN
- 0021-9797
No coin nor oath required. For personal study only.
✦ Synopsis
As part of a fundamental study of the electrophoretic deposition of phosphor particles, a suspension composed of (\mathrm{Zn}{2} \mathrm{SiO}{4}) : Mn (P-1) or ZnS:Ag (P-11) phosphor particles in isopropyl alcohol (IPA) containing various nitrate salts was characterized by conductivity and zeta-potential measurements. Dissociation constants and limiting ionic mobilities of (\mathrm{NaNO}{3}, \mathrm{Mg}\left(\mathrm{NO}{3}\right){2}), and (\mathrm{Y}\left(\mathrm{NO}{3}\right){3}) in IPA were determined from conductivity measurements. It was found that the dissociation constants are very low and decrease as the metal ion valency increases. The zeta potential of the phosphors was measured in IPA under a wide range of salt concentrations and (\mathrm{pH}) values. In all cases, the zeta potential was approximately (-40 \mathrm{mV}) at salt concentrations less than (10^{-6} \mathrm{M}). As the concentration of (\mathrm{Mg}\left(\mathrm{NO}{3}\right){2}, \mathrm{Y}\left(\mathrm{NO}{3}\right){3}), or (\mathrm{Al}\left(\mathrm{NO}{3}\right){3}) increased, the zeta potential increased and became positive, reaching a maximum of approximately (40 \mathrm{mV}) at (10^{-5}) (M). In IPA or IPA containing (10^{-5} \mathrm{M} \mathrm{Mg}\left(\mathrm{NO}{3}\right){2}), the zeta potential was positive at (\mathbf{p H}<6), but became negative for (\mathrm{pH}>6). The zeta potential remained positive at all (\mathrm{pH}) values for (\mathrm{Mg}\left(\mathrm{NO}{3}\right)_{2}) concentrations of (10^{-4}) and (10^{-3} \mathrm{M}). The dependence of zeta potential on salt concentration was modeled using the Gouy-Chapman-Stern-Grahame model of the double layer. Using low values of capacitance for the inner and outer Helmholtz planes and a large adsorption potential, the model results agreed well with the experimental data. 1994 Academic Press, Inc.