Synthesis of advanced scintillators via vapor deposition techniques
Transparent optical ceramic coating materials have been fabricated from europium-doped lutetium oxide (Lu 2 O 3 :Eu) using physical vapor deposition and chemical vapor deposition techniques. The non-pixilated film coatings have columnar microcrystalline structure and excellent properties for use as radiological scintillators, namely very high density, high effective atomic number, and light output and emission wavelength suitable for use with silicon-based detectors having a very high quantum efficiency. The materials can be used in a multitude of high speed and high resolution imaging applications, including x-ray imaging in medicine.
1. A method of preparing a radiological scintillator coating material by chemical vapor deposition (CVD), the method comprising the steps of:
(a) providing LuCl 3 , EuCl 3 , CO 2 , and H 2 as reactants and a substrate to be coated with the scintillator coating material;
(b) reacting the reactants in a CVD reactor, whereby a scintillator coating comprising Lu 2 O 3 and Eu 2 O 3 is deposited onto the substrate.
2. The method of claim 1 , wherein the reactor is a cold wall reactor.
3. The method of claim 1 , wherein the reaction is carried out with input gas ratios in the range of 0.2 to 2.0% Cl 2 , 2.0 to 40% CO 2 , 10 o 30% Ar, with the balance being H 2 .
4. The method of claim 1 , wherein the reaction is carried out at a substrate temperature in the range of about 900° C. to about 1400° C.
5. The method of claim 1 , wherein the LuCl 3 and EuCl 3 reactants are generated in the reactor by reacting Cl 2 gas with Lu metal and Eu metal.
6. The method of claim 5 , wherein the temperature and flow rates are regulated so as to avoid the buildup of solid LuCl 3 on the Lu metal and Eu metal surfaces.
7. The method of claim 1 resulting in a preferentially oriented columnar grain growth of the scintillator coating.
8. The method of claim 1 , further comprising the step of:
(c) annealing the scintillator coating by heat treatment at a temperature in the range of about 100 to 1400° C.