A reflection mode fiber optic oxygen sensor that can operate at high temperatures for power plant applications is being developed. The sensor is based on the {sup 3}O{sub 2} quenching of the red emission from hexanuclear molybdenum chloride clusters. One of the critical materials issues is to demonstrate that the luminescent cluster immobilized in the sol-gel porous support can withstand high temperature. At the same time the sol-gel matrix must have a high permeability to oxygen. Using a potassium salt of the molybdenum clusters, K{sub 2}Mo{sub 6}Cl{sub 14}, we have established the conditions necessary for deposition of optical quality sol-gel films. From spectroscopic measurements of the film we have shown that the cluster luminescence is stable following heat cycling of 1 hour at 250 C. Quenching of a factor of 4X between pure nitrogen and 21% oxygen was observed for films cured directly at 200 C. These are promising results for a high temperature fiber optical oxygen sensor based on molybdenum chloride clusters.

In this report, initial results pertaining to the synthesis molybdenum clusters and characterization using absorption, optical microscopy, and x-ray powder diffraction are discussed. The synthesis was performed according to literature [1], but results from x-ray powder diffraction indicate that the synthesis did not give the desired compound. The absorption and optical microscopy indicate that the compound synthesized has properties similar to the desired Mo{sub 6}Cl{sub 12} clusters [2,3], so it is unclear as of yet what happened. The sample cell for performing high temperature spectroscopy on thin films of the molybdenum clusters at elevated temperature in a controlled gas environment was designed and an initial prototype was built.