Mid-infra-red hollow waveguides have been applied to the detection of gases and vapours using a wavelength-tunable laser. The waveguides effectively operate as intrinsic sensors with the passage of small volumes of gas or vapour through the bore. An enhancement to analyte sensitivity has been investigated by several means using rigid and flexible hollow waveguides configured to provide extensions to the interacting optical path. The precision of measurement of absorbance is shown to reduce and then ultimately limit the minimum detection levels as the optical interaction path increases. Trace measurement of ethylene at sub-ppm levels (parts per million volume) is demonstrated with waveguide gas cells operating at elevated pressures over path lengths of several metres. For trichloroethylene and 2-furaldehyde, the minimum detection is less than 10 ppm under similar experimental conditions.

The microstructures of ferroelectric glass‐ceramics derived from (Pb,Sr,Ba)Nb2O6 solid solutions have been investigated systematically using electron microscopy (TEM, SEM) and X‐ray diffraction (XRD). These data, together with the measured dielectric properties of the materials, have been correlated with both the sintering/devitrification conditions and compositional changes to the base glass. The low incidence of ferroelectric domains suggests that an increase in permittivity results from an increase in internal stress during grain growth. These domains were observed only in a few tetragonal structured crystals with grain sizes >1 μm. Their compositions were typically Sr‐rich and Ba‐depleted. For a given devitrification/crystallization temperature, the grain compositions and sizes are affected significantly by relatively minor compositional changes to the base glass network formers. The diffuse temperature dependence of permittivity is attributed to the fine‐grain (submicrometer) microstrucutres and the compositional range of solid solutions which arise during devitrification.

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