Strontium cobaltite coated optical sensors for high temperature carbon dioxide detection

Carbon dioxide sorption on perovskite type metal oxide, Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ, was studied at high temperatures for the development of a high temperature optical carbon dioxide sensor. When exposed to carbon dioxide in 600-700 °C Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ reacts with carbon dioxide to form Sr_0.6Ba_0.4CO₃. The sorption capacity increases with carbon dioxide pressures. The perovskite structure of the metal oxide after carbon dioxide sorption can be recovered by exposing the material to air at a temperature higher than 680 °C. The sorption rate with temperature and the high temperature sorption mechanism can be described by the homogeneous model. The optical sensor uses Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ as the sensing material and long period fiber gratings as the optical component. The Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ coated long period fiber grating (LPFG) can measure carbon dioxide in the concentration range of 1-30% in air (1 atm total pressure) at 600 and 700 °C. The sensor maintains its functionality after several repeated cycles of carbon dioxide detection at 700 °C.