Study On Colossal Dielectric Properties Of Cr-based Ceramic Materials

With the advent of the microelectronics era,electronic components tend to be miniaturized and integrated.Colossal dielectric materials have been the focus of miniaturization and integration of electronic components.Due to the many shortcomings of the existing colossal dielectric materials,the search for new colossal dielectric materials has become one of the hot issues in the field of dielectrics.Recent reports indicate that Cr-based oxide materials exhibit "good"dielectric behavior,Apart from the CDC behavior,the Cr-based oxides materials also shows other rich properties,such as superconductivity,half metal,ferromagnetism,and magnetodielectric effects,which make this structure the most promising candidate for dielectric materials This makes such oxides one of the most promising candidates for dielectric materials.On the other hand,the formation mechanism of colossal dielectric behavior in colossal dielectric materials is still controversial.More and more studies have shown that colossal dielectric behavior is related to the double relaxation model.Based on this,this paper takes SrCrO4,Sr2TiCrO6,CuCrO2 three kinds of Cr-based ceramic materials as the research object,and systematically studies its dielectric properties,and deeply explores the relationship between colossal dielectric behavior and double relaxation mechanism.The full text is summarized as follows:(1)Study on dielectric properties of SrCrO4 ceramics.Dielectric properties of SrCrO4 were systematically investigated in the frequency range of 102 to 106 Hz and temperature range of 5 to 890 K.Colossal dielectric behavior near room temperature and relaxor-like dielectric behavior around 730 K with an extremely dielectric constant up to 1.62×105 were found.Dual relaxation mechanism composed of a dipolar and a Maxwell-Wagner relaxations is found to be responsible for the colossal dielectric behavior.The dipolar relaxation at low temperature is related the defect dipole pair of OHo·-Cr3+ caused by chemically absorbed water.while Maxwell-Wagner relaxation near the room temperature results from grain boundaries.The relaxor-like dielectric behavior is associated with the hopping motion of oxygen vacancies which leads to a high-temperature relaxation.(2)Study on dielectric properties of Sr2TiCrO6 ceramics.The dielectric properties of the Sr2TiCrO6 samples were studied systematically in the temperature range of 50-890 K.Colossal dielectric behavior was found to occur near room temperature and two dielectric anomalies were observed around 620 and 820 K.The colossal dielectric behavior follows the dual relaxation mechanism,which is composed of a dipolar relaxation associated with the defect dipole pairs of OHo·-Cr3+ and an Maxwell-Wagner relaxation due to the surface-layer effect originated from humidity sensitivity.The low-temperature anomaly is considered to be a pseudo-relaxor behavior caused by oxygen vacancies and the high-temperature anomaly results from negative capacitance due to the carriers changing from localized state to free state.(3)Study on the dielectric properties of CuCrO2 ceramics.The dielectric properties of CuCrO2 ceramics at low temperature(10-300 K)were studied systematically.It was found that there were two relaxations at low temperature:the dipolar relaxation at lower temperature was caused by defect dipole pairs of OHo·-Cr3+,and the Maxwell-Wagner relaxation at higher temperature was caused by the surface layer effect originated from humidity sensitivity.Two relaxations lead to colossal dielectric behavior near room temperature.