【摘要】 利用瓦特计技术,研究了YBa₂Cu₃O_7-y烧结样品和粉末熔化法（PMP）织构样品在77K和50Hz交变磁场下的交流（ac）损耗（?）实验结果表明,ac损耗（?）同外磁场振幅H_m之间遵从幂函数规律:（?）∝H_mⁿ对于YBa₂Cu₃O_7-y的烧结样品:（1）当H_m<40Oe时,这样低的磁场已穿透弱连接的晶粒边界网络,导至晶粒间的损耗,（?）∝H_m^1.6;（2）当40Oe≤H_m<170Oe时,中等磁场破坏了晶粒间的耦合,并且磁通穿进了晶粒内,引起不完全穿透的晶粒内损耗,（?）∝H_m³;（3）当H_m≥170Oe时,磁场完全穿透晶粒,产生完全穿透的晶粒内损耗,（?）∝H_m。烧结样品晶粒内的ac损耗与Bean模型符合。当H_m约从5Oe增加到1400Oe时,烧结样品的（?）从10^-7W/cm²增加到10^-3W/cm²。对于YBa₂Cu₃O_7-y的PMP织构圆柱样品:（1）当平行于样品轴的磁场振幅H_m≤100Oe时,由样品表面的粗糙度、空隙等引起的损耗,（?）∝H_m^1.2;（2）当H_m>100Oe时,磁通穿透进样品引起不完全穿透损耗,（?）∝H_m³,这也与Bean模型符合。在H_m>630Oe的较高磁场下,织构样品的ac损耗比烧结样品的大。更多还原

【Abstract】 AC losses at 77K for sintered and PMP textured YBa2Cu3O7-y specimens have been measured by an ac wattmeter in 50Hz sinusoidal-wave applied magnetic field. The relation of ac loss P versus amplitudes of magnetic field were found to follow a power law: P∝Hmn, where n varies from 1 to 3 in various regions of applied magnetic field Hm. The magnetic field dependence of ac losses in sintered specimens of YBa2Cu3O7-y can be subdivided into three regions. (l)In low field region (HM < 40 Oe), magnetic fields easily penetrate the weak-link grain boundary network leading to an inter-granular ac loss, which is proportional to HM1.6; (2) In the second region (40 Oe ≤ Hm <170Oe), the moderate magnetic fields cause a decoupling of grains and flux partially penetrated into grains leads to a intra-granular ac loss, which is proportional to HM3; and (3) In the third region (Hm ≥ 170Oe), magnetic fields penetrate full grains leading to a ac loss, which is proportional to Hm. The intra-granular ac losses of sintered samples for the latter two regions are well coin-cident with Bean model. When the field amplitude Hm varies from 5Oe to 1400Oe, the ac losses of sintered samples increase from 10-7W/cm2 to 10-3 W/cm2. When the amplitude of the field parallel to the a-b planes is smaller than 1400Oe, the magnetic field dependence of ac losses in PMP textured specimens of YBa2Cu3O7-y can be subdivided into two regions. (l)In the first region (Hm < l00Oe), roughness and voids of the surface of the sample cause ac loss, which is proportional to Hm1.2; (2)In the second region (Hm ≥ 100Oe), magnetic fields penetrate the samples lea-ding to the ac loss in the partial penetration state, which is proportional to Hm. In the region (2), the ac loss of textured specimens of YBa2Cu3O7-y also are well coincident with Bean model. In the high-field region of Hm > 630 Oe, the ac loss of textured samplis is larger than the sintered samples.更多还原