The Doppler broadening lineshape of 5llkeV gamma rays of positron annihilation radiation in the high Tc superconductors Y-Ba-Cu-O has been investigated.The lineshape parameters as a function of temperature were measur...The Doppler broadening lineshape of 5llkeV gamma rays of positron annihilation radiation in the high Tc superconductors Y-Ba-Cu-O has been investigated.The lineshape parameters as a function of temperature were measured from 85K to 300K.Anomalous dependence of lineshape parameters on temperature was first observed in polyphase samples,i.e.,the lineshape parameters occurred catastrophe for some narrow temperature regions(90K.107K,115K and 180K).This anomaly is probably due to the migration and redistribution of oxygen vacancies in the samples during superconducting transition.展开更多
In high temperature oxide superconductors, such as Sr-La-Cu-O,Ba-Y-Cu-O, there is a phase transition from semiconductor to metal as the composition changes under the same condition of heat treatment. Recently the theo...In high temperature oxide superconductors, such as Sr-La-Cu-O,Ba-Y-Cu-O, there is a phase transition from semiconductor to metal as the composition changes under the same condition of heat treatment. Recently the theoretical explanations are proposed, hut the research is still at an initial stage. Thus study in different ways on the cause of the phase transition and its relationship with high temperature superconductivity is one of the important current subjects.展开更多
文摘The Doppler broadening lineshape of 5llkeV gamma rays of positron annihilation radiation in the high Tc superconductors Y-Ba-Cu-O has been investigated.The lineshape parameters as a function of temperature were measured from 85K to 300K.Anomalous dependence of lineshape parameters on temperature was first observed in polyphase samples,i.e.,the lineshape parameters occurred catastrophe for some narrow temperature regions(90K.107K,115K and 180K).This anomaly is probably due to the migration and redistribution of oxygen vacancies in the samples during superconducting transition.
文摘In high temperature oxide superconductors, such as Sr-La-Cu-O,Ba-Y-Cu-O, there is a phase transition from semiconductor to metal as the composition changes under the same condition of heat treatment. Recently the theoretical explanations are proposed, hut the research is still at an initial stage. Thus study in different ways on the cause of the phase transition and its relationship with high temperature superconductivity is one of the important current subjects.
