Xinjiang Institute of Physics and Chemistry has made progress in the study of the linearization mechanism of high-temperature heat-sensitive ceramic materials
Due to the semiconducting properties of grains and grain boundaries, polycrystalline oxide ceramic materials have enriched the diversity of their applications in the field of functional ceramic materials. However, how to tune the grain band structure and grain boundary barrier through defect engineering is crucial for the realization of high-performance electronic devices.
Recently, the research team of Chang Aimin from the Xinjiang Institute of Physics and Chemistry, Chinese Academy of Sciences, through the study of the grain and grain boundary effects of CaCu3Ti4O12 (CCTO) ceramic materials, deeply analyzed the nonlinear physical mechanism of the electrical properties of CCTO ceramic materials in the high temperature region; induced by Fe3+ The energy band structure of the CCTO ceramic material realizes the linearization of the electrical properties of the CCTO ceramic material in the high temperature region.
Fig. Linearization mechanism in high temperature region of CaCu3Ti4O12 based thermosensitive materials
Combining impedance spectroscopy and first-principles analysis methods, the team found that the grain resistivity of CCTO ceramic materials will show abnormal PTC (PTC, Positive Temperature Coefficient) characteristics after 575 K, which is the cause of CCTO ceramic materials lnρ- The main reason for the nonlinearity of the 1000/T curve in the high temperature region. Fe3+ can change the energy band structure of CCTO materials. First-principles calculations show that Fe3+ doping narrows the forbidden band of the material and induces new impurity energy levels in the forbidden band, which is consistent with the impedance spectrum obtained. It is consistent with the conclusion that the dependence of grain resistivity and temperature is shifted to the low temperature region. This shift results in no monotonic change in grain resistivity within the application temperature region, thereby enhancing the linearity of the lnρ-1000/T curve of CCTO materials in the high temperature region. In addition, Fe3+ can adjust the activation energy of CCTO materials in a wide range by changing the activation energy of grain boundaries, thereby expanding the application temperature range of CCTO ceramic materials. The research method is based on the regulation mechanism of Fe3+ doping on ceramic grains and grain boundaries, which provides a new way for the research of polycrystalline semiconductor ceramic materials.
