Abstract
AbstractThe electrical conductivity of NH4 Br single crystals is measured by both ac and dc techniques over the temperature range 50 to 130 °C. The dc conductivity as a function of temperature in both, pure and Cd2+ doped NH4Br samples shows excellent Arrhenius behavior. The activation enthalpy for conduction is 1.14 eV. Ac measurements exhibit a pronounced frequency dependent plateau at lower temperatures (≈ 50 to 100 °C). This plateau is believed to be due to a “proton loss”. Due to the existence of the plateau that masks any extrinsic region, the dc technique is more useful in the study of ionic defects in NH4Br. Assuming that transport is due to a vacancy mechanism, the enthalpy of vacancy migration is estimated to be 0.55 eV. The polarity of the vacancy is not uniquely determined.
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