METHOD OF MAKING PHOTOLUMINESCENT SAMARIUM-DOPED TITANIUM DIOXIDE PARTICLES
The disclosure provides a process for preparing photoluminescent samarium-doped titanium dioxide, typically in the rutile phase, comprising: precipitating, preferably at a pH of about 2 to about 3, a mixture comprising hydrated titanium oxide, a source of samarium, and a separable filtering agent to form a precipitated mixture comprising precipitated samarium-doped hydrated titanium oxide and the separable filtering agent; filtering the precipitated mixture to form a filter cake comprising the precipitated samarium-doped hydrated titanium oxide and the separable filtering agent; calcining the precipitated samarium-doped hydrated titanium oxide and separable filtering agent at a temperature of greater than about 300° C. to form a mixture comprising samarium-doped titanium dioxide and the separable filtering agent; and removing the separable filtering agent to recover samarium-doped titanium dioxide particles.
1 . A process for preparing photoluminescent samarium-doped titanium dioxide comprising:
(a) precipitating a mixture comprising hydrated titanium oxide, a source of samarium, and a separable filtering agent to form a precipitated mixture comprising precipitated samarium-doped hydrated titanium oxide and the separable filtering agent;
(b) filtering the precipitated mixture to form a filter cake comprising the precipitated samarium-doped hydrated titanium oxide and the separable filtering agent;
(c) calcining the precipitated samarium-doped hydrated titanium oxide and separable filtering agent at a temperature of greater than about 300 C to form a mixture comprising samarium-doped titanium dioxide and the separable filtering agent; and
(d) removing the separable filtering agent to recover samarium-doped titanium dioxide particles.
2 . The process of claim 1 wherein the mixture comprising hydrated titanium oxide and the separable filtering agent is prepared by reacting titanium tetrachloride or titanium oxychloride with MOH wherein M is selected from the group consisting of NH 4 , Group 1 metal, and mixtures thereof, in the presence of a solvent.
3 . The process of claim 2 wherein the Group 1 metal is selected from the group consisting of Na, K, Li and Rb.
4 . The process of claim 2 wherein the solvent is selected from the group consisting of water, water containing at least one metal halide, water containing at least one ammonium halide, neat alcohol, alcohol containing at least one metal halide and alcohol containing at least one ammonium halide, aldehyde, ketone, nitrile, and ether and mixtures thereof.
5 . The process of claim 4 wherein the alcohol is selected from the group of methanol, ethanol, n-propanol, iso-propanol, and butyl alcohol isomer and mixtures thereof.
6 . The process of claim 1 wherein the separable filtering agent is MCl wherein M is selected from the group consisting of NH 4 , Group 1 metal, and mixtures thereof.
7 . The process of claim 6 wherein the Group 1 metal is selected from the group consisting of Na, K, Li and Rb.
8 . The process of claim 2 wherein the precipitating step is carried out at a pH of about 2 to about 3.
9 . The process of claim 8 wherein the samarium-doped titanium dioxide particles are predominantly in the rutile phase.
10 . The process of claim 1 wherein the calcining temperature is above about 300° C.
11 . The process of claim 1 wherein the separable filtering agent is NH 4 Cl.
12 . The process of claim 1 wherein the separable filtering agent is removed by washing with water or a solution comprising water.
13 . The process of claim 1 wherein the samarium-doped titanium dioxide particles are exposed to heat at a temperature up to and including 800° C.