摘要
本文研究了冷压（2.2～5.2GPa）与热压（2.2GPa, 2.50～950℃）对YBa2Cu3O7-σ的正交→四方相转变区和超导电性的影响。冷压保持其正交结构,但破坏了超导性,在98 K（失超点）到室温呈半导体特性,丙在空气中烧结,可恢复液氮温区的零电阻状态。 以Cu锅密封样品,热压处理至950℃,不发生Cu的析出。热压处理后,98K（失超点）到室温呈半导体特性,再经通氧烧结,于 86K出现零电阻。热压处理过程,从 150～950℃为正交→四方转变区。950℃为转变结束温度,大大高于氧气、空气、氮气、真空状态的温度。400℃附近为起始转变温度,低于氮气、氧气气氛的温度。因此相变区加宽。T0-T 结束温度升高,与Cu锅的抑制还原作用有密切关系。如降低高压淬火速率（<<102℃/s）,或随后辅以氧气氛中的后处理,将有利于获得既有高密度又有高 Tc的 YBa2Cu3O7-σ超导体。
In this paper, the influences of cool- and hot-pressure treatment were studied on the phase transition region from or thorhombic to tetragonal and superconductivity in YBa2Cu3O7-δ. After the cool pressure treatment of 2.2-5.2GPa. the samples remained the orthorhombic structure, but lost their superconductivities and kept up the semiconductivity in the region from 98K to room temperature. If the sampes are sintered in air, their zero resistance states will be regained.When the samples were sealed hermetically into a 'Cu bowl', there was no separation of Cu in the samples within the region of hot-pressure temperature from 250℃ up to 950c℃. After the hot-pressure treatment (2.2GPa. 250-95010 .the samples were in semiconductiviting state in the region of 98K to room temperature. If the samples are followed by an after-treatment in oxygen.the zero resistance state can be observed (at about 86K). In the process of hot-pressure treatment.it was found that the transition region of orthorhombic to tetragonal is in the 450-950℃, 950℃ is the end temperature of transition, which is higher than that of samples obtained by sintering in oxygen, air, nitrogen and vacuum. And about 400℃ is the onset temperature of transition, which is lower than that in nitrogen, air and oxygen.Therefore the phase transition region is widened, and the end temperature of T0-r raises. These are related to that the 'Cu bowl' restrains the reduction role under high pressure. If the quenching rate under high pressure is slowed (<<102℃/s), or the samples are followed by an after-treatment in O2. the YBa2Cu3O7-δ both with high density and Tc can be obtained. The deficiency and hole of oxygen are also discussed here.
出处
《高压物理学报》
CAS
CSCD
北大核心
1990年第4期246-253,共8页
Chinese Journal of High Pressure Physics
基金
国家自然科学基金
国家教委博士点基金
关键词
YBa2Cu3O7-б
冷压
热压
结构
相变
Y Ba2Cu3O7-δ, cool- and hot-pressure treatment, structure transition, superconductivity, reduction role and high pressure, oxygen deficiency.
