PHOTOACOUSTIC DETECTION OF WATER-VAPOR PERMEABILITY IN ZRO2-TIO2 CERAMIC

The photoacoustic detection of water vapour permeability in solids is discussed, We propose a new experimental configuration in which the ph otoacoustic heat source is located at the cell's optical entrance wind ow, rather than at the sample-transducer gas interface. It is claimed that only the sample permeability property is experimentally accessed in the new configuration. The experimental arrangement is tested by me asuring the water vapour permeability of a ZrO2-TiO2 ceramic sample. I n these measurements we were able to detect changes in the air molar c oncentration of water as small as 1.1%, with a resolution better than 0.5%, corresponding to the lowest relative humidity used in our measur ements.