ZnOの電気的特性に及ぼすBe添加の影響

概要

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For identifying the mechanism of ferroelectric phase transition in Li-doped ZnO, the electrical properties of Be-doped ZnO were studied. Be2+ ion has the same electronic condition and small ionic radius to Li+ ion. The temperature dependence of measured dielectric constant has two dielectric anomalies as in Li-doped ZnO. First peak at about 370[K] and second one at about 420[K] are related to the surface and to the inside of the ceramic sample, respectively. It is considered that the ferroelectric phase transition takes place in Be-doped ZnO as in Li-doped ZnO. As the measured resistivities of Be-doped ZnO at the room temperature were abnormlally low, the temperature dependences of electric conductivity were examined. It was found that the electric conductivity curve, plotted in ln σ vs. 1/T, has two regions approximated by straight lines with different gradients. The thermal activation energies calculated from the gradient of the straight line is considerably smaller than the band gap of ZnO. To investigate the high electric conductivity measured in Be-doped ZnO, the frequency dependence of impedance, Z, was examined by using the alternating current impedance method.