新型1223相高T_c超导层型铜氧化物(Tl,M)(Sr,Ba)_2Ca_2Cu_3O_z(M=Cr,V)

NEW 1223 TYPES OF HIGH-T_C SUPERCONDUCTING LAYERED CUPRATES (T1,M) (Sr,Ba)_2Ca_2Cu_3O_z (M=Cr,V)

纯的TlSrCaCuO体系难以制备1223型超导铜氧化物,报道了合成和用粉末X射线衍射、电子衍射鉴定了一大类新型1223相高T_c超导层型铜氧化物(Tl_(1_x)M_s)(Sr_(2_y)Ba_y)Ca_2Cu_3O_x,其中M为Cr或V,包括(Tl_(0.75)Cr_(0.25)(Sr_(2_y)Ba_y)Ca_2Cu_3O_x,(Tl_(0.75)V_(0.25))(Sr_(2_y)Ba_y)Ca_2Cu_3O_x,(Tl_(1_x)Cr_x)Sr_2Ca_2Cu_3O_x和(Tl_(1_x)V_x)Sr_2Ca_2Cu_3O_5等4个系列1223相层型铜氧化物。在M存在的情况下,适量的Ba部分取代Sr,有利于(Tl,M)基1223相化合物的形成,然而,当y=0,即无Ba存在时,过量Tl对(Tl,M)基1223相化合物的形成十分必要。电阻和交流磁化率测量都显示,有Ba存在时的这些化合物超导电性T_c(ρ=0)均在100K以上,(Tl_(0.75)Cr_(0.25))(Sr_0.5Ba_1.50)Ca_2Cu_3O_x的T_c(ρ=0)可达113K,纯Sr系列掺V1223相化合物的超导电性略高于相应的掺Cr的化合物的超导电性,其中(Tl_0.75V_0.25)Sr_2Ca_2Cu_3O_x的T_c(ρ=0)可达105K。此外,作者还详细研究和讨论了M(Cr或V)量和Sr/Ba比对(Tl,M)基1223型铜氧化物形成和超导电性的影响。

It is difficult to synthesize superconducting cuprate TlSr2Ca2Cu3Oz. In this pa-per. we report that new 1223 types of superconducting layered cuprates (Tl1-xMx) (Sr2-yBayCa2Cu3Ox (M=Cr,V) containing (Tl0.75Cr0.25)(Sr2_y)Bay)Ca2Cu3Oz, (T10.75-V0.25)(Sr2-yBay)Ca2Cu3Ox, (Tl1-xCrx)Sr2Ca2Cu3Ox and (Tl1-xVx)Sr2Cu3Oz have been synthesized and identified by using X-ray diffraction and electron diffraction. It is helpful for formation of (T1,M)-1223 phase to substitute proper amount of Ba for Sr. However, when y=0, excess amount of Tl is necessary for formation of (Tl, M)-1223 cuprate. Resistivity and AC magnetic measurement indicate that the zero resistance temperature of the cuprates (y=0) are all higher than 100 K, the T_c (ρ=0) of (Tl0.75Cr0.25)(Sr0.50Ba1.50)Ca2Cu3Oz is up to 113K. The superconducting critical temperature of Ba free V-doped 1223 cuprates are slightly higher than those of Cr-doped 1223 cuprates, the Tc(ρ=0) of (Tl0.75V0.25)Sr2Ca2Cu3Oz is up to 105 K. The effect of the amount of M(Cr,V) and ratio of Sr/Ba on the formation and su-perconductivity of (T1,M)-1223 cuprate was also studied and discussed in detail.