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Polycrystalline soft ferrites, Zn x Cu 1−x Fe 2 O 4 (x = 0.30, 0.50, 0.70, 0.80 and 0.90), doped with controlled amounts of calcium chloride (CaCl 2 ) were prepared by standard ceramic techniques. The samples were characterized using X-ray and IR techniques. These compounds are being developed as humidity sensing materials with a final aim of developing a sensor. The temperature dependence of the dc resistivity (ρ) was studied by the usual two-probe method from room temperature to 500 °C. Parameters such as resistivity (ρ) and activation energy (∆E) were computed and the results discussed on the basis of existing theories.

Polycrystalline soft ferrites, Zn x Cu 1-x Fe 2 O 4 (x = 0⋅ ⋅30, 0⋅ ⋅50, 0⋅ ⋅70, 0⋅ ⋅80 and 0⋅ ⋅90), doped with controlled amount of calcium chloride (CaCl 2) were prepared by standard ceramic route and studied for a.c. susceptibility. X-ray diffraction studies of the compositions reveal formation of single-phase cubic spinel. The values of lattice constant increase as doping percentage of CaCl 2 increased from 0⋅ ⋅01% to 0⋅ ⋅05% and afterwards decrease slightly. The presence of chlorine ions is confirmed by absorption peak in far IR spectra near 650 cm-1 for all the samples. The variation of a.c. susceptibility with temperature shows the existence of single domain structure for x = 0⋅ ⋅3 and exhibits transition from single domain to multidomain structure with increased Ca 2+ contents from 0⋅ ⋅01 to 0⋅ ⋅1%. The composition, x = 0⋅ ⋅5, shows multidomain structure independent of Ca 2+ content. The samples for x = 0⋅ ⋅70, 0⋅ ⋅80 and 0⋅ ⋅90 show paramagnetic behaviour at and above room temperature.

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