Optical and electrochemical gas sensing properties of yttrium–silver co-doped lithium iron phosphate thin films

The new sensing material, LiFe0.995Y0.0025Ag0.0025PO4 was synthesized using hydro-thermal methods, and characterized by X-ray diffraction, energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The as prepared products were subsequently utilized in a self assembled optical waveguide gases testing apparatus and a WS-30A electro-chemical gas sensing apparatus for xylene detection. A glass optical waveguide gas sensor was fabricated by spin-coating a LiFe0.995Y0.0025Ag0.0025PO4 thin film on the surface of single-mode tin-diffused glass Optical Waveguide. The sensing elements for electro-chemical gas sensor were made by dip-coating a LiFe0.995Y0.0025Ag0.0025PO4 thin film on the surface of an alumina ceramic tube, assembled with platinum wire. The experimental results indicated that, at room temperature, LiFe0.995Y0.0025Ag0.0025PO4 thin film/tin-diffused optical waveguide sensing element exhibited higher response to xylene in the range of 0.1–100 ppm; at an optimum operating temperature (300 °C), the response (Sr) of LiFe0.995Y0.0025Ag0.0025PO4 to 100 ppm of xylene was 5.29, as measured by the WS-30A electro-chemical gases sensing apparatus.