Nd0.7 Sr0.3MnO3 ceramics with secondary phases were prepared by ball-milling and post heat- treatment at 1623 K for 3,7 and 13h,respectively.The results from x-ray diffraction and energy dispersed spectroscopy show th...Nd0.7 Sr0.3MnO3 ceramics with secondary phases were prepared by ball-milling and post heat- treatment at 1623 K for 3,7 and 13h,respectively.The results from x-ray diffraction and energy dispersed spectroscopy show that some secondary phases are introduced and grow gradually with sintering time.These secondary phases have significant effects on the ac transport.For all the samples,the real part of impedance (Zr) decreases with increasing frequency and the Zr peak moves to a higher temperature.Interestingly,for a given frequency the Zr peak decreases with sintering time.However,for samples B and C which were sintered for a longer time than sample A,an additional Zr peak appears at a higher temperature and gradually increases with sintering time.The reposition of trapped charges in phase/grain boundaries or secondary phases is supposed to be responsible for the unusual relaxation process.展开更多
Electrical transport properties of the interface between a Nd_(0.7)Sr_(0.3)MnO_(3) ceramic and a Ag electrode are investigated using the ac impedance over a wide temperature and frequency ranges.The ac impedance measu...Electrical transport properties of the interface between a Nd_(0.7)Sr_(0.3)MnO_(3) ceramic and a Ag electrode are investigated using the ac impedance over a wide temperature and frequency ranges.The ac impedance measurements give the compressed semicircle arcs at different temperatures,which are used for the analysis of different contributions to electrical transport based on an electrical equivalent circuit.A significant interface-dependent electroresistance effect of 530% is clearly developed around the metal-insulator transition temperature 130K,which is confirmed as the interface-layer dependent Curie temperature by the plot of interfacial conductance with frequency at different temperatures.展开更多
基金Supported by the Program for New Century Excellent Talents in University under Grant No NCET-08-0674.
文摘Nd0.7 Sr0.3MnO3 ceramics with secondary phases were prepared by ball-milling and post heat- treatment at 1623 K for 3,7 and 13h,respectively.The results from x-ray diffraction and energy dispersed spectroscopy show that some secondary phases are introduced and grow gradually with sintering time.These secondary phases have significant effects on the ac transport.For all the samples,the real part of impedance (Zr) decreases with increasing frequency and the Zr peak moves to a higher temperature.Interestingly,for a given frequency the Zr peak decreases with sintering time.However,for samples B and C which were sintered for a longer time than sample A,an additional Zr peak appears at a higher temperature and gradually increases with sintering time.The reposition of trapped charges in phase/grain boundaries or secondary phases is supposed to be responsible for the unusual relaxation process.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10774040,11174073 and 10911120055/A0402the Program for New Century Excellent Talents in University under Grant No NCET-08-0674the Joint Chinese-Russian Project under Grant No 08-02-92205。
文摘Electrical transport properties of the interface between a Nd_(0.7)Sr_(0.3)MnO_(3) ceramic and a Ag electrode are investigated using the ac impedance over a wide temperature and frequency ranges.The ac impedance measurements give the compressed semicircle arcs at different temperatures,which are used for the analysis of different contributions to electrical transport based on an electrical equivalent circuit.A significant interface-dependent electroresistance effect of 530% is clearly developed around the metal-insulator transition temperature 130K,which is confirmed as the interface-layer dependent Curie temperature by the plot of interfacial conductance with frequency at different temperatures.
