A. Sree Rama Murthy

Application of principal component analysis to gas sensing characteristics of Cr0.8Fe0.2NbO4 thick film array.

The transient changes in resistances of Cr0.8Fe0.2NbO4 thick film sensors towards specified concentrations of H2, NH3, acetonitrile, acetone, alcohol, cyclohexane and petroleum gas at different operating temperatures were recorded. The analyte-specific characteristics such as slopes of the response and retrace curves, area under the curve and sensitivity deduced from the transient curve of the respective analyte gas have been used to construct a data matrix. Principal component analysis (PCA) was applied to this data and the score plot was obtained. Distinguishing one reducing gas from the other is demonstrated based on this approach, which otherwise is not possible by measuring relative changes in conductivity. This methodology is extended for three Cr0.8Fe0.2NbO4 thick film sensor array operated at different temperatures.

Application of principal component analysis to the conductometric Cr 1−x Fe x NbO 4 (x = 0, 0.5, 1.0) thick films gas sensors

The gas sensing characteristics of Cr1-xFexNbO4 (x = 0.0, 0.5, 1.0) towards different organic analytes and hydrogen were investigated at different operating temperatures. The slope of the retrace transient, a representative feature for desorption kinetics was considered for data exploration. 11 sensors with 12 samples were tested and the data obtained was processed using principal component analysis (PCA). The scores plot and loadings plot showed the possible differentiation of the cross sensitive analytes and redundancy of the sensor behaviour towards these analytes respectively.

Low temperature synthesis of Ni and Co substituted alloys of Pd and their hydrogen sensing characteristics

Palladium and palladium alloys (nickel, cobalt and nickel co-substituted) were prepared using low temperature chemical reduction technique at 300 K. The synthesized metal and alloys were deposited using PLD on alumina substrate. The deposited nanostructured thin film alloys showed much better sensitivity towards hydrogen between the concentrations of 2000 and 20000 ppm of hydrogen than pure palladium thin film at 300 K.

Conductometric Sensing of H 2 by Chromium Niobate

Investigations on chromium niobate (CrNbO4) have shown that the material responds to a wide hydrogen concentration range of 0.01%-0.40% at 613 K. The conductivity of CrNbO4 is independent of oxygen partial pressure and offers to be a promising candidate for monitoring H2 in radioactive spent fuel storage facilities. Reduction of metal ions to lower valence states during hydrogen sensing was evidenced by X-ray photoelectron spectroscopic studies.

Comparison of Hydrogen Sensing Characteristics of CrNbO4 Prepared by Solid-State Route and Solution Combustion Synthesis (SCS)

Solution combustion synthesis is adopted for the preparation of CrNbO4. Its electrical conductivity is found to be less than that of the solid state synthesized compound. Hydrogen sensing property of solution-synthesized compound is comparable to that of solid-state prepared compound up to about 400 vppm of H2. However, the sensor signal saturates beyond 2500 vppm of H2. Hydrogen sensing property is compared between the combustion derived and solid state prepared compounds.