Proceedings of the Beijing International Workshop on HIGH TEMPERATURE SUPERCONDUCTIVITY

Transcription

1 Progress in High Temperature Superconductivity - Vol. 2 Proceedings of the Beijing International Workshop on HIGH TEMPERATURE SUPERCONDUCTIVITY Beijing, P R China, 29 June 1 July 1987 Editors: Z Z Gan & G J Cui Department of Physics Beijing Institute of Modern Physics Peking University and G Z Yang & Q S Yang institute of Physics Academia Sinica Beijing, China UNIVERSITATSBIBLIOTHEK^ HANNOVER TECHN'SCHE lnformationsb.sl.oth.ek, World Scientific Singapore New Jersey Hong Kong

2 CONTENTS UNiVERS.TATSBIBLIOTHEK' HANNOVER TECHNISCHE INFORMATiONS^EUOTHEK PREFACE, MATERIALS RECENT HIGH T c SUPERCONDUCTIVITY RESEARCH AT IBM THOMAS J.WATSON RESEARCH CENTER (Invited Paper) D. R. Clarke HIGH T c SUPERCONDUCTIVITY OF ReBaCuO OXIDES (Invited Paper) Z. X. Zhao PROCESSING, STRUCTURE, AND HIGH-TEMPERATURE SUPERCONDUCTIVITY (Invited Paper) E M Engler, R. B. Beyers, V. Y. Lee, A. Nazzal, G. Lim, S. S. P. Parkin, P. B. Grant, J. E. Vazquez, M. L. Ramirez and R. Jacowitz Y-Ba-Cu-0 SUPERCONDUCTORS AT THE UNIVERSITY OF NEW SOUTH WALES K. N. R. Taylor, G. J. Russell, L. B. Harris, R. A. Vaile, J. Cochrane, D. Matthews, T. Puzzer, H. B. Sun, A. Bailey, S. Bosi and M. LaRobma SUPERCONDUCTORS WITH HIGH ZERO-RESISTANCE TEMPERATURE IN Ln-Ba-Cu -O SYSTEM (Ln=Gd, Dy, Ho, Er, Tm, Yb, and Lu) Y Z Huang, G. H. Chen, L. Q. Chen, Z. H. Mai, X. Chu, Q. S. Yang, Y' M Ni, Q. R. Liu, L. Z. Wang, R. M. Tang, J. Q. Bi, C. Q. Wang, S. L. Jia, C. G. Cui, S. S Q. Q Guo,, S. L. Li and Z. X. Zhao THREE TETRAGONAL PHASES RELATED TO THE ORTHORHOMBIC " T ^ ^ ^ ^ D. V ta 39 A NEW AVENUE OF IMPROVING THE BEHAVIORS OF Y-Ba-Cu-0 SUPERCONDUCTING CERAMICS F. C. Yin, S. T. Chen, J. M. Liu, F. Y. Liu, H. T. Sun, X. Q. Wu, B. T. Yang and X. Yao STRUCTURE AND PROPERTIES OF YBa 2 Cu _ y IN THE NORMAL AND SUPERCONDUCTING STATE P. Vasitev, I. Z. Kostadinov, M. Mateev, P. Gladkov, M. Mikhov, J. Nikolov, T. K. Kalkandjiev and S. Sevov SUPERCONDUCTING PROPERTIES OF Y - Ba - Cu - Pt _ O V. T. Kovachev, E. C. Vlakhov, K. A. Nenkov, V. A. Lovchinov, M. M. Gospodinov, A. K. Stojanov and D. A. Dimitrov THE MICRO-REGION COMPOSITIONAL VARIATION OF YjBajCugO, SINGLE PHASE SUPERCONDUCTOR Z. H. Mai, L. Q. Chen, X. Chu, D. Y. Dai, Y. M. Ni, Y.Z.Huang, Z. L. Xiao, P. W. Ge and Z. X. Zhao y ^ ^ ^

3 RELATIONSHIP BETWEEN THE X-RAY DIFFRACTION PATTERN AND T c OF Ln-Ba-Cu-0 SYSTEM WITH PEROVSKITE STRUCTURE J. F. Wang, H. Z. Liu, C. G. Zheng, H. Guo, D. F. Xu, Y. Z. Lin, J. X. Qian, Y. C. Du, G. R. Shen, H. C. Gao, J. G. Wu and G. X. Xu.... INVESTIGATION ON Y 1 _ y Ce x Ba 2 Cu _ y SUPERCONDUCTOR Z. Xianyu, D. X. Li, T. G. Chen, D. J. Li, J. E. Hong, Y. F. He, R. J. Li, Z. M. Xiu, R. P. Gao, F. Liu, Q. H. Zhao, X. Y. Mao and W. Sun... SUPERCONDUCTIVITY IN Y(Ba x Srj_ x )CuO SYSTEM J. X. Liu, Y. C. Chang, X. Y. Shao, N. Cao, Z. G. Duan, X. D. Zou, H. Fan, D. S. Hou, Q. Z. Ran, J. Q. Zheng and W. Y. Guan Y-Ba-Cu-0 SUPERCONDUCTING CERAMICS S. B. Tian, X. F. Li, T. L. Wen, Z. X. Lin, S. C. Li and H. J. Yu HIGH T c SUPERCONDUCTIVITY AND STRUCTURE OF Y-Ba-Cu OXIDES REPLACED PARTIALLY BY La AND Li Y. H. Xu, Z. R. Li, C. R. Li, H. Wang, W. Li and X. D. Lin THERMAL CHARACTERIZATION AND SUPERCONDUCTIVITY OF THE Th 5 _ x Ba x Pb 2 _ 05x Cu 5 O 13 + y Y. L. Zhang, S. S. Xie, X. R. Cheng, K. S. Li, Q. S. Yang, Y. M. Ni, G. R. Liu and J. K. Liang PLASMA SPRAYED HIGH T c SUPERCONDUCTOR L. S. Wen, S. W. Qian, Q. Y. Hu, B. H. Yu, H. W. Zhao, K. Guan, L. S. Fu and Q. Q. Yang SOME FACTORS EFFECT ON ZERO-RESISTANCE TEMPERATURE OF SUPERCONDUCTOR YjBa 2 Cu _ x L. Q. Chen, Z. L. Xiao, Y. Z. Huang, Z. H. Mai, X. Chu, D. Y. Dai, Z. X. Zhao, G. H. Chen, Y. M. Ni, J. Q. Bi, L. Z. Wang and C. Q. Wang MEISSNER EFFECT ON SUPERCONDUCTING YBaCu OXIDE J. L. Yan, K. X. Shi, S. Y. Din, Z. Yu, P. Gao and L. Qiu A STUDY OF SUPERCONDUCTING OXIDE Y-Ba-Cu-Sn-0 X. Jin, H. M. Shao, G. Q. Wang, M. Lu, H. H. Zhang, C. Y. Lin, W. M. Chen, J. B. Ji, J. M. Zhang and J. W. Zhao SUPERCONDUCTIVITY IN Y-Ba-Cu(Cr)-0 SYSTEM Z. Xianyu, R. J. Li, Q. H. Zhao, L. Q. Liu, Q. T. Wang, Y. F. He, Z. M. Xiu, D. X. Li, Z. B. Shao, T. G. Chen, R. P. Gao, Y. Tu, Y. Li, H. Y. Jin, D. J. Li, J. E. Hong, F. Liu, Z. J. Liu, Y. Q, Jia and J. Q. Sun DETERMINATION OF OXYGEN NON-STOLCHIOMETRIC FRACTION, 6, IN SINGLE-PHASE SUPERCONDUCTING YBa 2 Cu 3 0 m + 6 C. L. Ji, C. M. Cui, S. L. Liu, K. H. Wang, Z. G. Fan and G. F. Zhang STRUCTURE NEUTRON DIFFRACTION STUDY ON Y- Ba - Cu - O B. S. Zhang, C. T. Ye, Z. Yang, L. Jin, S. Gan, S. L. Li, H. Hu, X. M. Zheng, F. X. Chen, W. J. Zhang, C. Y. Li, K. Wu and K. X. Chen 125

4 PREPARATIVE AND STRUCTURAL STUDIES ON THE SUPERCONDUCTING PHASE YBa 2 Cu _ d Y. Q. Tang, B. X. Ling, W. J. Zhang, Z. Y. Liu, X. M. Zheng, N. Z. Wu, M. C. Shao, C. Y. Li, K. X. Chen and J. Z. Li 129 HREM STUDY ON THE DEFECTS OF Y-Ba-Cu-0 SUPERCONDUCTORS Y. H. Liang, J. Chen, L. C. Wang, Y. Yian, X. Q. Pan, M. Wei, X. Jin, G. Q. Wang and D. Feng 145 TEM STUDY OF DEFECTS IN HIGH T c SUPERCONDUCTOR SINGLE CRYSTAL YBa 2 Cu 3 O 7 M. S. Hu, X. N. Zhao, P. Chen, Y. Tao, H. X. Lu, J. Wu, S. Y. Ding, Z. Yu, P. Gao, Q. Li and D. Feng 149 CRYSTAL STRUCTURE AND DEFECT OF SUPERCONDUCTING OXIDES F. H. Li, H. J. Fan, X. J. Wu and J. G. Zhao 153 PHASE RELATION, CRYSTAL STRUCTURE AND SUPERCONDUCTIVITY IN Ba-La-Cu-O SYSTEM C. Dong, J. K. Liang, G. C. Che, S. S. Xie, Z. X. Zhao, Q. S. Yang, Y. M. Ni and G. R. Liu 157 A STUDY OF YBa 2 Cu 3 O 9 _ 6 TYPE SUPERCONDUCTING SINGLE CRYSTALS H. X. Lu, J. Wu, X. Y. Zhang, X. K. Gao, X. J. Li, M. S. Hu, H. N. Zhou, X. Y. Mao, T. X. Wang, H. Q. Xin and Y. B. Shi 161 THE RELATIONSHIP BETWEEN THE STRUCTURE AND PROPERTY OF THE HIGH T c SUPERCONDUCTOR YjBa 2 Cu _ y DETERMINED BY THE DYNAMIC LOW TEMPERATURE X-RAY DIFFRACTION METHOD G. W. Pei, J. Yan, Y. T. Liu, D. Y. Song, M. G. Liu, B. R. Liu, S. Y. Liu, X. M. Yang and G. S. Wang 165 SUBSOLIDUS PHASE RELATIONSHIPS AND SUPERCONDUCTIVITY IN Gd 2 O 3 -BaO-CuO SYSTEM J. K. Liang, X. T. Xu, G. H. Rao, S. S. Xie, X. Y. Shao and Z. G. Duan 171 THE COMPOSITION AND STRUCTURE OF Y-Ba-Cu-0 SUPERCONDUCTORS Z. Y. Hua, C. L. Jia, H. S. Cheng, Y. M. Cai and A. R. Jiang 175 MICROSTRUCTURAL STUDY OF HIGH T c Y-Ba-Cu-0 J. Zhang, H. Gu, J. Xu, S. Gai and D. Yin 185 SUPERLATTICE STRUCTURE IN HIGH-TEMPERATURE SUPERCONDUCTING Y-Ba-Cu-0 SYSTEM K. Godwod, J. Gorecka and J. Majewski 189 HREM OBSERVATION OF STRUCTURAL DEFECTS IN YBa 2 Cu _ x CERAMICS S. L. Wen, J. W. Feng, X. Y. Song, L. S. Lu, C. H. Li, C. G. Li and D. Y. Li 193 STUDY ON PHASE DIAGRAM OF BaO-Y 2 O 3 -CuO TERNARY SYSTEM G. C. Che, J. K. Liang, W. Chen, S. S. Xie, Y. D. Yu, Q. S. Yang, Y. M. Ni, G. R. Lui and G. H. Chen 197 STUDY OF ANOMALIES ABOVE 90K IN POLYCRYSTALLINE YBa 2 Cu _ x BY X-RAY DIFFRACTION H. M. Shen, Y. N. Wang, H. N. Zhou, H. Q. Wang, Z. M. Niu, Z. F. Zhang, H. X. Lu, X. Y. Zhang and J. Wu 201

5 ELECTRON DIFFRACTION AND HIGH RESOLUTION ELECTRON MICROSCOPY STUDY OF THE SUPERCONDUCTOR IN Ba-Y-Cu-0 SYSTEM M. L. Sui and D. X. Li 205 THE EFFECT OF LATTICE DISTORTION AND DEFECT ON SUPERCONDUCTIVITY IN Y-B a-c u-0 SYSTEM G. W. Qiao, S. Z. Lin, X. P. Jiang, H. B. Qi, J. Lu, J. Zhou, X. B. Zeng and N. P. Zhu 209 APPLICATION OF XPS TO STUDYING Y-Ba-Cu-0 SUPERCONDUCTOR Y. Q. Tang, N. Z. Wu, L. L. Gui, B. X. Lin, X. M. Zheng, Z. Y. Liu, D. L. Yin, K. Wu, W. B. Zhang and Q. Z. Wen 213 PROPERTIES PHYSICAL PROPERTIES AND SUPERCONDUCTIVITY OF LAYERED PEROVSKITE OXIDES (Invited Paper) S. Tanaka, S. Uchida, H. Takagi, S. Tajima, T. Hasegawa, K. Kishio, K. Kitazawa and K. Fueki 219 ANISOTROPIC MAGNETIZATION IN SINGLE CRYSTAL YBa 2 Cu 3 O 7 (Invited Paper) R. N. Shelton, R. W. McCallum, M. A. Damento and K. A. Gschneidner, Jr 235 PHONON BEHAVIOR OF Y-B a-c u-0 SUPERCONDUCTOR AND SEMICONDUCTOR J. H. Ruan, J. Z. Li, A. S. Yu, S. Gan, T. H. Yang, J. Lin, S. W. Niu, C. Gou, C. T. Ye, Z. Y. Liu, X. M. Zheng, B. X. Lin, C. Y. Li and C. D. Wei 243 HIGH MAGNETIC FIELD HALL EFFECT AND MAGNETORESISTANCE STUDIES OF Y-Ba- Cu-O: A HIGH T c SUPERCONDUCTOR J. D. Hettinger, A. G. Swanson, J. S. Brooks, Y. P. Ma and Z. X. Zhao 247 SPECIFIC HEAT STUDY ON Y-Ba-Cu-0 SYSTEM Z. J. Chen, H. S. Yang, D. N. Zheng, B. M. Wu, K. Q. Wang, Y. Zhao, Z. Y. Chen, Y. T. Qian and Q. R. Zhang 253 PERSISTENT CURRENT AND ITS DECAY IN YBaCuO SAMPLES W. J. Yeh, L. Chen, F. Z. Xu, B. K. Bi and P. R. Yang 255 SUPERCONDUCTIVITY AND MAGNETISM IN THE HIGH T c SUPERCONDUCTORS ReBa 2 Cu 3 0? _ x WITH Re= Y, Dy, Gd, Sm, Nd AND La S. Q. Feng, X. Zhu, C. Lin, C. D. Wei, Z. X. Liu, Y. X. Sun, K. Wu, Z. H. Shen, J. Z. Li, Z. Z. Gan, F. X. Chen, J. W. Chen, N. Li and J. S. Liu 259 SPECIFIC HEAT STUDY OF HIGH T c SUPERCONDUCTOR YBa 2 Cu _ x F. Li, Q. Li, G. Lu, K. Wu, Y. Zhou, C. Li and D. Yin 265 POSITRON ANNIHILATION STUDY OF HIGH T c SUPERCONDUCTOR YBaCuO IN THE REGION NEAR TRANSITION TEMPERATURE M. K. Teng, D. X. Shen, L. Chen, C. Y. Yi and G. H. Wang 269 STUDY OF ANOMALOUS ELASTICITY OF YBa 2 Cu _ x IN K Y. N. Wang, M. Gu, J. S. Zhu, H. M. Shen, Z. R. Xu, Z. M. Niu, H. X. Lu, S. Y. Din, X. Q. Gao, K. M. Tan and Z. Yang 273 SUPERCONDUCTING AND MAGNETIC PROPERTIES OF YBa 2 Cu S + y SYSTEM P. Przyslupski, J. Igalson, M. Baran, W. D. Dobrowolski, T. Skoskiewicz and J. Rauluszkiewicz 277

6 CHARACTERIZATION AND PROPERTIES OF PHASES IN THE SUPERCONDUCTING SYSTEM Y-Ba-Cu-0 S. X. Dou, A. J. Bourdillon, C. C. Sorrell, K. E. Easterling and N. Sawides 281 UPPER CRITICAL FIELD OF HIGH T c SUPERCONDUCTING OXIDES C. G. Cui, S. Q. Guo, S. L. Li, L. Chen, C. Dong, X. T. Xu and J. K. Liang 285 MAGNETISM AND SUPERCONDUCTIVITY IN THE HIGH-T C SUPERCONDUCTOR Y-Ba 2 Cu _ x C. Lin, G. Lu, Z. X. Liu, Y. X. Sun, J. Lan, G. Z. Li, S. Q. Feng, C. D. Wei, Z. Z. Gan, Z. Y. Liu, X. M. Zheng and B. X. Lin 289 MOSSBAUER SPECTRUM AND SUPERCONDUCTIVITY OF SINGLE PHASE Eu x Y l-x Ba 2 Cu H. X. Lu, X. Y. Zhang, X. K. Gao, J. Wu, X. Y. Mao, Y. C. Zhang, D. K. Sun, H. Q. Wang, J. P. Huang and R. Asher 295 MAGNETIZATION MEASUREMENTS OF Ba Q 6 Y Q 4 Cu0 3 _ y AND Ba 0 6 Y 0 4 _ x Sc x Cu0 3 _ y SYSTEMS Y. H.Shi, B. R. Zhao, H. S. Wang, Y. Lu, Y. Y. Zhao, P. Hsu and L. Li 299 EXPERIMENTAL STUDY ON THE MAGNETIC PENETRATION INTO Y-Ba-Cu-0 SUPERCONDUCTORS S. S. Yan, Q. P. Jia, X. Wang, G. Q. Xia and H. Ma 303 PHASE TRANSITION IN Ba-Y-Cu-0 COMPOUND AS PROBED BY POSITRON ANNIHILATION Y. J. He, M. Huang, W. Z. Yu, J. J. Xiong and L. Y. Cai 309 ANTIFERROMAGNETIC ORDERING IN Y-Ba-Cu-Pt-0 V. T. Kovachev, E. S. Vlakhov, K. A. Nenkov, V. A. Lovchinov, M. M. Gospodinov, A. K. Stojanova, D. A. Dimitrov and T. Mydlarz 313 TRANSPORT PROPERTIES IN SINGLE PHASE SUPERCONDUCTOR Ba 2 YCu _ 5 Y. Z. Ruan, X. L. Hu, Y. Zhao, Y. T. Qian, Z. Y. Chen, R. P. Wang and Q. R. Zhang 319 MOSSBAUER EFFECT STUDY OF THE E u-y-b a-c u-0 SUPERCONDUCTOR W. M. Xu, X. X. Liu, M. Z. Jin, L. Y. He, Y. F. Wang, J. S. Zhou, H. J. Liu, L. P. Li and W. H. Su 325 ULTRASONIC MEASUREMENTS IN YBa 2 Cu _ 6 X. R. Zhang, C. G. Qian, C. M. Gan, Z. N. Lu, S. Y. Zhang, H. Wang, N. S. Zhou, Z. J. Wang and Q. Ma 329 A STUDY OF INTERNAL FRICTION AND YOUNG'S MODULUS OF A HIGH T c SUPERCONDUCTOR YBa 2 Cu _ x J. J. Du, H. Q. Yin, O. Mao, X. Wang, J. Y. Jiang, W. G. Yao, J. S. Sun and L. Liu 333 ENERGY GAP OF HIGH T c SUPERCONDUCTOR YBa 2 Cu _ 5 H. Y. Ye, W. Lu, Z. Y. Yu, X. C. Shen, B. C. Miao, Y. M. Cai and Y. J. Qian 337 MAGNETIZATION OF HIGH T c SUPERCONDUCTING Ba -Y-Cu-0 S. Q. Guo, Q. S. Yang, G. R. Liu, C. G. Cui, S. L. Li, Y. Z. Huang, G. H. Chen, J. Q. Bi, L. Q. Chen and Z. X. Zhao 343

7 OBSERVATION OF A HIGH FREQUENCY PHONON MODE IN THE Y-Ba-Cu-0 SYSTEM J. Q. Liu, W. K. Wang, D. W. Chang, X. M. Huang, Y. Y. Wang, G. H. Chen and K. P. Zou 347 ULTRASONIC STUDY OF HIGH T c SUPERCONDUCTING SYSTEM Y. S. He, B. W. Zhang, S. H. Lin, J. Xiang, Y. M. Lou and H. M. Chen 351 THE BEHAVIOR OF Y-B a-c u-o SUPERCONDUCTING OXIDE IN SMALL MAGNETIC FIELD B. Zhou, J. W. Qiu, Z. M. Tong, B. C. Miao and Y. J. Qian 355 MAGNETISM AND HIGH T c SUPERCONDUCTIVITY IN (RE)Ba 2 Cu SYSTEMS (RE = Sc, La, Sm, Gd, Dy, Ho, Er, Yb AND Lu) K. Kadowaki, Y. K. Huang, M. van Sprang, H. P. van der Meulen, J. Q. A. Koster, J. C. P. Klaasse, A. A. Menovsky and J. J. M. Franse 359 DC SUSCEPTIBILITY OF HIGH T c SUPERCONDUCTORS Y-Ba-Cu-0 SYSTEM S. Y. Zhang, H. Whang, N. S. Zhou, Z. J. Wang and X. Ma 363 DEVICES HIGH T c THIN FILMS WITH ZERO-R AT 84K BY MULTILAYER DEPOSITION (Invited Paper) Z. Bao, F.Wang, Q.Jiang, S.Wang, Z. Ye, K.Wu.C. Li and D.Yin 369 JOSEPHSON DEVICES FABRICATED WITH HIGH T c YBaCuO THIN FILMS (Invited Paper) G. J. Cui, X. F. Meng, S. G. Wang, K. Shao, H. M. Jiang, Y. D. Dai, Y. Zhang, R. P. Peng, Z. L. Bao, F. R. Wang, S. Z. Wang, Z. Y. Ye, C. Y. Li, K. Wu and D. L. Yin 375 JOSEPHSON FREQUENCY MIXING BETWEEN TWO Ka BAND SIGNALS IN CERAMIC BRIDGE AT LIQUID NITROGEN TEMPERATURES P. H. Wu, Q. H. Cheng, S. Z. Yang, M. H. Fan, Y. J. Feng, J. Chen, Y. Li, H.X.Lu.X.K. Gao, J.Wu and X.Y.Zhang 381 ELECTRON TUNNELING MEASUREMENTS OF ENERGY GAP IN SUPERCONDUCTOR YBaCuO, LaSrCuO AND BPBO H. J. Tao, Y. F. Chen, L. Lu, Q. S. Yang, B. R. Zhao, Y. H. Shi, Y. Lu, H. S. Wang, Y. Y. Zhao, L. Li, Y. Fang, J. X. Liu, L. Q. Chen, D. S. Tang and Q. Z. Wu 389 HIGH T c SUPERCONDUCTIVITY OF Sr-La-Cu-0 AND Ba-Y-Cu-0 THIN FILMS B. R. Zhao, L. Li, Y. Lu, H. S. Wang, Y. H. Shi, Y. Y. Zhao, C. W. Yuan and J. Gao 395 THE JOSEPHSON EFFECT IN CERAMIC BRIDGE AT LIQUID NITROGEN TEMPERATURE P. H. Wu, Q. H. Cheng, S. Z. Yang, J. Chen, Y. Li, Z. M. Ji, J. M. Song, H. X. Lu, X. K. Gao, J. Wu and X. Y. Zhang 399

8 STUDY OF SUPERCONDUCTING Y-Ba-Cu-0 THIN FILMS WITH ZERO RESISTANCE TEMPERATURE AT 77K J. Q. Zheng, G. G. Zheng, D. Q. Li, W. Wang, J. M. Xue, D. G. Xiao, L. Cao and W. Y. Guan 405 THE QUANTUM INTERFERENCE EFFECT OF THE MICROBRIDGE IN A Y-Ba-Cu-0 SUPERCONDUCTOR L. Chen, W. J. Yeh, F. Z. Xu, B. K. Bi and P. R. Yang 409 HIGH T c SUPERCONDUCTING THIN FILMS BY CHEMICAL SPRAY DEPOSITION G. Y. Meng, X. D. Wang, X. J. Oien, P. Z. Fu, P. H. Yang, D. K. Peng, F. Q. Li, W. D. Zhang, G. E. Zhou, J. Wang and Y. H. Zhang 413 TEMPERATURE AND MAGNETIC FIELD DEPENDENCE OF CRITICAL CURRENT OF YBaCuO JOSEPHSON JUNCTIONS P. Gao, H. C. Fan, X. X. Yao, Z. Yu, S. Y. Ding, X. N. Jing, K. X. Shi and J. L. Yan 417 OBSERVATIONS OF JOSEPHSON EFFECTS AND INVESTIGATIONS OF POSSIBLE CURRENT PATH IN Y-Ba-Cu-0 SUPERCONDUCTORS AT 77K G. J. Cui, X. F. Meng, S. G. Wang, Y. D. Dai, J. Z. Li, Y. Zhang, X. M. Ren, H. M. Jiang, T. Y. Yang, M. X. Yan, Y. C. Du, J. C. Mao, R. P. Peng, K. Shao, X. W. Wu, G. Z. Yan, Y. Z. Gao, G. Y. Wu, X. M. Zheng, Z. Y. Liu and F. X. Chen 421 THEORY A PHYSICAL MODEL FOR HIGH T c SUPERCONDUCTIVITY OF THE OXYGEN DEFICIENT PEROVSKITE Y-Ba-Cu-0 Z. Z. Gan, Y. D. Dai and R. S. Han 427 ELECTRON THEORY OF THE SUPERCONDUCTIVITY AND CRITICAL TRANSITION POINT T c OF Ba 2 YCu _ d (d=2) BY THE APPLICATION OF THE EMPIRICAL ELECTRON THEORY OF SOLIDS AND MOLECULES Ruihuang S. H. Yu 433 A CLUSTER STUDY OF MECHANISM IN THE NEW SUPERCONDUCTORS YBa 2 Cu Z. Zeng, Q. Q. Zheng and R. S. Han 441 ELECTRONIC STRUCTURE AND SUPERCONDUCTING MECHANISM IN La 2 _ y X y CuO 4 C. B. Zhang, S. M. Li, Y. G. Teng, W. X. Zhang, X. W. Zhang and S. G. Chen 447 THEORETICAL ASPECTS OF THE HIGH T c IN NARROW-BAND GOLDEN TRIANGLE D. L. Yin and R. S. Han 451 SUPERCONDUCTIVITY IN FREE CARRIER-BIPOLARON INTERACTING SYSTEM C. F. Chen and L. Y. Zhang 459 A NOTE ABOUT A MEAN FIELD THEORY OF RVB-SUPERCONDUCTIVITY MODEL Z. D. Wang, N. Z. Zou, J. Z. Pang, Q. Jiang and C. D. Gong 463

9 VIRTUAL BIPOLARONIC BOUND STATE AND HIGH T c OXIDE SUPERCONDUCTORS J. Li and C. D. Gong 467 HIGH T c Ba -Y- Cu - O COMPOUND "HOLE" CONDUCTIVITY PROPERTY W. Q. Shi, Z. Chai, B. Q. Li, S. X. Liu, X. J. Liu and Z. B. Hu 471 THE EFFECT OF LOCAL MODE ON T c OF THE OXIDE SUPERCONDUCTORS N. Z. Zou, Z. D. Wang, J. Z. Pang and C. D. Gong 475 PERCOLATED SUPERCONDUCTIVITY AND ELECTRON - ELECTRON EXCHANGE MECHANISM IN Ba-La-Cu-0 R. B. Tao 479