Xiao Yu Zhang,Min Xu,Wen Yao Yang,Sheng Zhu Cao,Yan Ju Yang,Jie Li,Xi Yuan Hao
The interlayer defects of diamond/copper (Cr) composite have been eliminated by adding holmium (III) oxide through Spark Plasma Sintering (SPS) method. The effects of Ho2O3 addition of diamond–copper interlayer on the microstructure and phase composition are investigated. The total density of states (DOS) and partial density of states (PDOS) are investigated by the first-principles calculations. It is revealed that the addition of Ho2O3 has a distinct modification effect on diamond–copper (Cr) interlayer. Obvious cracks around the diamond outer surface are hardly found, and the diamond particles are enfolded by the copper matrix. The Cr2C phase that beneficial to reduce interlayer defects and improve interlayer bonding was generated under the effect of adding Ho2O3. The thermal conductivity of diamond/copper (Cr-Ho2O3) is 686 W/(m·K). The possible reasons for doping Ho2O3 to eliminate interlayer defects and improve the thermal conductivity were discussed.
The structure and electrical properties of CaCu3Ti4O12 (CCTO) ceramics doped with xHo2O3 synthesized by solid-phase reaction method were systematically studied. Insights from X-ray diffraction (XRD) measurements indicate the existence of a primary phase of CCTO in all samples. Ho2O3 dopant was found to inhibit grain growth and thus leading to a reduced grain size of ceramics. Moreover, the distribution of resistivity with temperature revealed the manifestation of a negative temperature coefficient (NTC) effect in the samples. More specifically, the resistivity (ρ20) values of obtained ceramics configurations decreased from 8.54 × 106 to 1.76 × 105 Ω cm with increasing Ho2O3 doping content. In addition, thermal constant (B20/75) of all samples was higher than 4000 K. Electrical properties analysis disclosed that electron hopping process is main conduction mechanism within CCTO-based ceramics. In addition, insights from complex impedance spectra revealed the existence of grain boundaries with resistance higher than grains resistance. This effect is strongly connected with the manifestation of electrical relaxation procedures within grain boundaries. Our outcomes verify that both the structural configuration and the electrical performance of the CCTO-based ceramics can be tuned directly and effectively by incorporating Ho2O3 dopant.
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