Copper (Cu) nanoparticles (NPs) were prepared by sol–gel process, and superconducting (Cu0.5Tl0.5)Ba2Ca2Cu3O10−δ {(CuTl)-1223} phase was synthesized by conventional solid-state reaction. The desired (Cu)x/(CuTl)-1223, x = 0–4.0 wt% composites, were obtained by adding Cu NPs in superconducting (CuTl)-1223 phase. These composites were characterized by X-ray diffraction, DC-resistivity versus temperature (R–T) and AC conduction measurements. The tetragonal crystal structure with P4/mmm space group of the host superconducting (CuTl)-1223 phase remained dominant after the addition of Cu NPs. The zero-resistivity critical temperature Tc(0) (K) was increased, and normal state resistivity was decreased after addition of Cu NPs in CuTl-1223 phase. The frequency- and temperature-dependent AC conduction properties of (Cu)x/(CuTl)-1223 composites were explored via dielectric, impedance and electric modulus measurements. The dielectric constant (ɛr/, ɛr//) and loss tangent (tanδ) were suppressed, while AC conductivity (σac) was improved with the addition of Cu NPs in (CuTl)-1223 phase. Comparatively, the capacitance associated with grain boundaries regions was found to be greater than the capacitance associated with grain regions. The capacitive behavior of the grain boundaries was decreased, while that of the grains was increased with increasing operating temperature for all these composite samples. The shifting of peaks in imaginary part of the electric modulus (M//) versus frequency (f) spectra toward lower frequency regime with increasing Cu NPs contents in superconducting (CuTl)-1223 phase is witnessed for the existence of non-Debye relaxation in the material.

中文翻译：

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(Cu)x/(CuTl)-1223 纳米粒子-超导体复合材料中的交流传导机制

铜 (Cu) 纳米粒子 (NPs) 通过溶胶-凝胶工艺制备，超导 (Cu0.5Tl0.5)Ba2Ca2Cu3O10-δ {(CuTl)-1223} 相通过常规固态反应合成。通过在超导 (CuTl)-1223 相中添加 Cu NPs 获得所需的 (Cu)x/(CuTl)-1223, x = 0-4.0 wt% 复合材料。这些复合材料通过 X 射线衍射、直流电阻率与温度 (R-T) 和交流传导测量进行表征。添加Cu NPs后，主体超导(CuTl)-1223相的具有P4/mmm空间群的四方晶体结构仍然占主导地位。在CuTl-1223相中加入Cu NPs后，零电阻率临界温度Tc(0) (K)升高，常态电阻率降低。通过介电、阻抗和电模量测量研究了 (Cu)x/(CuTl)-1223 复合材料的频率和温度相关的交流传导特性。介电常数 (ɛr/, ɛr//) 和损耗角正切 (tanδ) 受到抑制，而交流电导率 (σac) 通过在 (CuTl)-1223 相中添加 Cu NPs 得到改善。相比之下，发现与晶粒边界区域相关的电容大于与晶粒区域相关的电容。对于所有这些复合样品，晶界的电容行为降低，而晶粒的电容行为随着工作温度的升高而增加。