TY - JOUR
T1 - Preparation, formation kinetics, and properties of polycrystalline Nd1.85Ce0.15Cu4-y obtained from a sol-gel precursor
AU - Jardim, R. F.
AU - Ben-Dor, L.
AU - Maple, M. B.
PY - 1993/9/10
Y1 - 1993/9/10
N2 - Polycrystalline samples of Nd1.85Ce0.15CuO4-y obtained from a sol-gel precursor were sintered and reduced under different conditions and studied by high resolution X-ray powder diffraction, electrical resistivity, and magnetic susceptibility measurements. X-ray diffraction measurements showed that the precursor, which is non-crystalline at temperatures as high as 300 °C, undergoes several decomposition steps up to about 500 °C, where the beginning of Nd2-xCexCuO4-y (x≈0) formation is observed. At 700 °C, the predominant phase is Nd2-xCexCuO4-y which coexists with CuO and CeO2. Single-phase Nd1.85Ce0.15CuO4-y is obtained by heat treating the precursor in air at 1000 °C for 20 h. Electrical resistivity measurements on samples sintered below and above the eutectic temperature, and reduced under different conditions, reveal a semiconductor-like temperature dependence of the normal-state electrical resistivity. In addition, a striking double resistive superconducting transition with a Josephson-like lower temperature transition seems to be a common characteristic of these polycrystalline samples. Magnetic susceptibility measurements reveal a significant diamagnetic contribution at 5 K which occurs only below the Josephson coupling temperature. These features are discussed within the framework of a granular superconductor model.
AB - Polycrystalline samples of Nd1.85Ce0.15CuO4-y obtained from a sol-gel precursor were sintered and reduced under different conditions and studied by high resolution X-ray powder diffraction, electrical resistivity, and magnetic susceptibility measurements. X-ray diffraction measurements showed that the precursor, which is non-crystalline at temperatures as high as 300 °C, undergoes several decomposition steps up to about 500 °C, where the beginning of Nd2-xCexCuO4-y (x≈0) formation is observed. At 700 °C, the predominant phase is Nd2-xCexCuO4-y which coexists with CuO and CeO2. Single-phase Nd1.85Ce0.15CuO4-y is obtained by heat treating the precursor in air at 1000 °C for 20 h. Electrical resistivity measurements on samples sintered below and above the eutectic temperature, and reduced under different conditions, reveal a semiconductor-like temperature dependence of the normal-state electrical resistivity. In addition, a striking double resistive superconducting transition with a Josephson-like lower temperature transition seems to be a common characteristic of these polycrystalline samples. Magnetic susceptibility measurements reveal a significant diamagnetic contribution at 5 K which occurs only below the Josephson coupling temperature. These features are discussed within the framework of a granular superconductor model.
UR - http://www.scopus.com/inward/record.url?scp=0027659099&partnerID=8YFLogxK
U2 - 10.1016/0925-8388(93)90434-O
DO - 10.1016/0925-8388(93)90434-O
M3 - ???researchoutput.researchoutputtypes.contributiontojournal.article???
AN - SCOPUS:0027659099
SN - 0925-8388
VL - 199
SP - 105
EP - 114
JO - Journal of Alloys and Compounds
JF - Journal of Alloys and Compounds
IS - 1-2
ER -