Control of partial pressure of oxygen in the ppm range based on a two metal–oxide buffer system

Abstract

An innovative oxygen loading system which controls the partial pressure of oxygen (pO2) in a continuous inert gas stream in the range 10−4–10−7bar is developed and successfully tested. It relies on adjusting the electro-chemical equilibrium in a metal oxide buffer via temperature control. The buffer consists of a mixture of small 1.5mm diameter spheres composed of Cu2O and CuO. The buffer system is integrated into a furnace and heated to the operational temperature range below 900°C. A continuous inert gas stream is guided through the buffer system while at operating temperature. The performance of the loading system is verified by comparing the pO2 values, which are deduced via the buffer temperature following the Ellingham diagrams with the readout of a conventional zirconia-based oxygen sensor. The measured curve follows the Ellingham diagram for this material system within the error margin. The system reveals a fast response time and allows for active control of the partial pressure of oxygen in a laminar streaming inert gas atmosphere with low complexity.