Issue 3, 2012

The microwave cavity perturbation technique for contact-free and in situ electrical conductivity measurements in catalysis and materials science

Abstract

We have developed a noncontact method to probe the electrical conductivity and complex permittivity of single and polycrystalline samples in a flow-through reactor in the temperature range of 20–500 °C and in various gas atmospheres. The method is based on the microwave cavity perturbation technique and allows the simultaneous measurement of microwave conductivity, permittivity and of the catalytic performance of heterogeneous catalysts without any need for contacting the sample with electrodes. The sensitivity of the method towards changes in bulk properties was proven by the investigation of characteristic first-order phase transitions of the ionic conductor rubidium nitrate in the temperature range between 20 and 320 °C, and by studying the temperature dependence of the complex permittivity and conductivity of a niobium(V)-doped vanadium-phosphorous-oxide catalyst for the selective oxidation of n-butane to maleic anhydride. Simultaneously, the catalytic performance was probed by on line GC analysis of evolving product gases making the technique a real in situ method enabling the noninvasive investigation of electronic structure–function relationships.

Graphical abstract: The microwave cavity perturbation technique for contact-free and in situ electrical conductivity measurements in catalysis and materials science

Supplementary files

Article information

Article type
Paper
Submitted
12 Aug 2011
Accepted
16 Nov 2011
First published
18 Nov 2011

Phys. Chem. Chem. Phys., 2012,14, 1302-1312

The microwave cavity perturbation technique for contact-free and in situ electrical conductivity measurements in catalysis and materials science

M. Eichelbaum, R. Stößer, A. Karpov, C. Dobner, F. Rosowski, A. Trunschke and R. Schlögl, Phys. Chem. Chem. Phys., 2012, 14, 1302 DOI: 10.1039/C1CP23462E

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