Giant dielectric behavior of solution-growth CuO ceramics subjected to dc bias voltage and uniaxial compressive stress

This paper reports the influence of the dc bias voltage and uniaxial compressive stress on the giant dielectric properties of solution-growth CuO ceramics sintered at 900 (PR-900) and 950 °C (PR-950) for 10 h in air. The dielectric constants at room temperature and 1 kHz for both samples are respectively about 1.40 × 104 and 1.43 × 104 which can be explained by Debye-like relaxation based on a Maxwell-Wagner polarization. The external resistance forming at the interface between electrode and surface sample and the dielectric constant of both ceramics decrease with increasing dc bias voltage (0–4 V) due to the decrease in electrode capacitance, whereas the resistance of internal parts such as grain and grain boundary resistance remains constant. Interestingly, it is found that the dielectric properties of the ceramics also depend strongly on the applied compressive stress. The ɛ′ and tanδ (measured at 1 kHz) of PR-900 (PR-950) sample increase, respectively, up to the maximum values of 2.6 × 106 (6.16 × 106) and 263 (132) at the applied stress of 63 MPa (79 MPa). The mechanism responsible for this dielectric behavior is discussed based on the electrode effect.

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