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We report the acoustic imaging frequency dynamics of ferroelectric domains by low-frequency acoustic probe microscopy based on the commercial atomic force microscopy It is found that ferroelectric domain could be firstly visualized at lower frequency down to 0.5 kHz by AFM-based acoustic microscopy The frequency-dependent acoustic signal revealed a strong acoustic response in the frequency range from 7kHz to 10kHz, and reached maximum at 8.1kHz. The acoustic contrast mechanism can be ascribed to the different elastic response of ferroelectric microstructures to local elastic stress fields, which is induced by the acoustic wave transmitting in the sample when the piezoelectric transducer is vibrating and exciting acoustic wave under ac electric fields due to normal piezoelectric effects.

Dielectric behaviour of Sr0.61Ba0.39Nb2O6 (61SBN) and Sr0.75Ba0.25Nb2O6 (75SBN) single crystals has been studied. It is observed that 61SBN has relatively low diffuseness as well as smaller relaxation compared to 75SBN. Increase in the configurational entropy imposed by the change in defect structure is suggested to be the origin of this behaviour. Analysis using Vogel–Fulcher expression and modified Curie–Weiss law give a signature of long-range polar order in 61SBN. The value of γ for 61SBN is closer to unity (1.14), where as for 75SBN it is 1.52. The fluctuation (in the orientation) of dipoles near dielectric maxima in SBN system is mediated by a paraelectric state.

Static and dynamic domain behavior of ferroelectric fluoride BaMgF4 single crystal was investigated using high-resolution piezoresponse force microscopy. High domain wall anisotropy was found in the as-grown BaMgF4 crystal. Antiparallel domain wall strain phenomena due to defects across the domain boundary were directly observed. The lateral domain growth in the inhomogeneous AFM tip field revealed the activation mechanism of the domain wall motion.

Two-colour holograms were recorded in a Tb-doped near-stoichiometric LiNbO3 crystal by use of extraordinary 778 nm beams for writing and an ordinary 350 nm beam for gating. The dependences of two-colour recording sensitivity and the saturated diffraction efficiency on the intensities of the recording and gating beams are presented. The saturated diffraction efficiency increased with total writing intensity, and then reached a saturated value of 56% at an intensity of 20 W cm−2. The sensitivity increased linearly with gating intensity at low intensity, and then saturated with a value of 0.08 cm J−1 at an intensity of 1.6 W cm−2. Fifty plane-wave holograms are recorded by the angle-multiplexing method and an M/# of 1.13 is obtained.

The isolated, six-side polygonal domain structures are observed in the orthorhombic as-grown BaMgF4 single crystal by optical microscope and atomic force microscope. The domain configurations demonstrate highly domain wall anisotropy along one principal crystal axis and polar–surface inhomogeneity. The anisotropic behaviour is due to the anisotropy of domain wall energy density in the thermodynamic equilibrium process, and the asymmetric domain surface phenomena is ascribed to the combined contribution from the local electric fields and structure defects-induced mechanical stress during the domain evolution process.

A two-dimensional mapping method was employed to investigate the homogeneity of optical parametric oscillator (OPO) performance, such as output power distribution, slope efficiency, and oscillation threshold, based on periodically poled 1 mol % Mg-doped stoichiometric LiTaO3 devices fabricated by single and multi-pulse methods. The output power decreased from the electrode-patterned face to the opposite face at low pump intensities and became homogenous over the aperture at high pump intensities. The devices fabricated by the two methods showed no large differences in OPO properties, except for better homogeneity in depth for multi-pulse devices. A large effective aperture (fluctuation < 10%) of 1.4×1.3 mm2 was obtained in both types of devices.

We demonstrate 43% slope efficiency for generation of ~3200 nm light, a wavelength considered to be ideal for laser induced ultrasound generation in carbon fiber reinforced plastic. High slope efficiency was obtained by optimizing crystal lengths, cavity length and mirror reflectivity using a two crystal optical parametric oscillator+difference frequency mixing (OPO+DFM) nonlinear wavelength conversion scheme. Mid-IR output >12 mJ was obtained from a 1064 nm Nd:YAG pump laser with 12 ns pulse width (FWHM) and containing pulse energy of 43 mJ. A compact, single temperature crystal oven is described along with some suggestions for improving the slope efficiency.

We have carried out electron tunnelling spectroscopy on single crystals with the use of a scanning tunnelling microscope at 4.2 K. A conductance peak structure was observed near zero bias voltage for the tunnelling along the Cu-O bonding direction. A clear superconducting gap was observed for the tunnelling along the Cu-Cu direction. Curves along the Cu-O and Cu-Cu directions are consistent with the -wave pairing symmetry which has line-nodes along the Cu-Cu direction, taking into account the periodic arrangement of surface oxygen atoms.

Nanoscale structures and physical properties are of fundamental interest, and thus variations in scanning probe microscopy techniques have been developed to understand nanoscale physical phenomena in basic research and potential technological applications. 1) Very recently, scanning near-field ultrasound holography has been developed that provides nanoscale-resolution images of the internal substructures of microelectronic materials and malaria parasites in red blood cells. 2) In the field of ferroelectrics, nanoscale domain structures of ferroelectric thin films, ceramics and single crystals can be imaged and controlled directly using piezoresponse force microscopy. 3–10) Besides, acoustic mode scanning force microscopy including atomic force acoustic microscopy, 11,12) ultrasonic force microscopy, 13–16) and scanning probe acoustic microscopy 17–21) have the advantage of visualizing nanoscale domain structures, elastic properties or subsurface configurations. In the present study, a type of alternating-force-modulated atomic force microscope (AFM) in the acoustic mode was developed by exciting acoustic waves on the piezoelectric transducer, which is fixed on a cantilever in the commercial AFM. This acoustic mode AFM was used to visualize the ferroelectric domains in BaTiO3 single crystals. An alternating force-modulated AFM, functioning in the acoustic mode, was set up by modifying a commercial AFM (SPA 400, SPI3800N, Seiko, Japan). A schematic sketch of the modified AFM is shown in Fig. 1. An external sinusoidal signal provided by a function generator (33120A, Agilent) was applied to the piezoelectric transducer attached to the cantilever, thereby inducing a periodical vibration in the cantilever/tip system. This modulated-tip vibration driven by the function generator emits a local stress field underneath the tip, resulting in an acoustic vibration inside the sample, which gives rise to a remarkable acoustic response of the ferroelectric microstructure due to physical phenomenal effects. The resultant acoustic signal carrying ferroelectric information was converted into an electrical signal through a piezoelectric lead zirconium titanate (PZT) ceramic transducer bonded onto the sample, and then fed to a lock-in amplifier (Model 7280 DSP, Signal Recovery Instrumentation) for detection. For the experiment, a 2-mmthick 90-mm-long Ti/Pt-coated silicon cantilever (Micro Mash, NSC12-B) with a spring constant of 14 N/m and a resonance frequency of 315 kHz was used. For the present study, we chose a 0.3-mm-thick (001)-oriented BaTiO3 single crystal. Figures 2(a) and 2(b) are a topography image and the corresponding acoustic image of a BaTiO3 single crystal, respectively, at a modulation frequency of 133.42 kHz. It can be clearly seen that the acoustic features are nearly the same as those of the topography image, indicating only slight variations in the surface microstructure after sample polishing. Figure 2(c) shows an acoustic image taken at a frequency of 1.419 MHz in the same scanning area. Unlike Fig. 2(b), a different acoustic response is clearly seen in Fig. 2(c), exhibiting remarkable acoustic contrasts in parallel strips about 300 nm in width, which are obviously the 90 ferroelectric domains in the BaTiO3 single crystal. The striped patterns are more distinguished in another large scanning area of 10 10 mm 2 measured at a frequency of 1.419 kHz, as shown in Fig. 3. The intercrossing domain phenomena shown in Fig. 3(b) reflect the domain state distribution at different depths throughout the specimen. Such phenomena were observed in Han and Cao’s studies of the averaged domain configurations using a polarized optical microscope, in which the domain configurations at various depths were exhibited in an optical image by adjusting the focus. 22)

A volume holographic filter operating in the reflection geometry at communication wavelengths was demonstrated in oxidized Fe-doped near-stoichiometric lithium niobate crystals, and the designed filter showed a narrow bandwidth of less than 0.2 nm and an express loss of more than 20 dB. An array of volume holographic filters was constructed in the same crystal with central wavelength separation of 0.5 nm.

Undoped and MgO (0.5 and 1.0-mol%)-doped near-stoichiometric LiTaO3 (SLT) crystals were grown from off-congruent Li-rich solutions (Li~60 mol%) by the double-crucible Czochralski method using a continuous SLT ceramic grain charging system. Curie temperatures of the undoped and MgO (0.5 and 1.0-mol%)-doped SLT crystals are 688, 694 and 695°C, respectively. The ordinary and extraordinary refractive indices (no, ne) of these crystals were measured by the prism coupling technique in the wavelength range from 0.440 to 1.050 µm at room temperature, and the temperature-independent Sellmeier equations for each crystal were derived from the measured refractive index data. no of the SLT crystal was almost the same as that of a congruent-melt LiTaO3 (CLT) crystal, while ne of the SLT crystal was lower than that of the CLT crystal. ne was lower than no for the SLT crystal, similar to as in the case of the LiNbO3 crystal. The refractive indices of the SLT crystal, no and ne, were found to be almost independent of MgO concentration at the doping level of 0.5 and 1.0 mol%.

The optical damage resistances of near-stoichiometric LiNbO3 (LN) crystals doped with MgO were investigated at λ=532 nm. Their refractive indices were also measured in the wavelength range from 440 to 1050 nm, from which Sellmeier's equations were derived. While the congruent LN (CLN) crystal required 5 mol% MgO to suppress the optical damage, the near-stoichiometric LN (SLN) crystal doped with 1 mol% MgO showed no optical damage up to the input intensity of 2 MW/cm2. The ordinary refractive indices (no) of MgO-doped SLN crystals decreased with MgO doping concentration up to 4.6 mol%. In contrast, the extraordinary refractive indices (ne) of MgO-doped SLN crystals were found to be almost independent of MgO doping concentration up to 4.6 mol%. With respect to optical device design, it is advantageous that ne of MgO-doped SLN crystal is almost independent of MgO doping concentration up to 4.6 mol% and that the SLN crystal needs only 1 mol% MgO to suppress optical damage.

The authors carried out a tunnelling spectroscopy measurement on a single crystal of superconducting oxide Bi2Sr2CaCu2O8- delta using a low temperature scanning tunnelling microscope. The superconducting gap parameter shows a spatial variation over a relatively small area ( approximately 10 nm). The authors obtained the energy gap parameter Delta (4.2 K)=26 meV, the most observable value, and correspondingly 2 Delta /kBTc=7, larger than the BCS value. The shape of the (dI/dV)-V curve suggests an anisotropy of the energy gap. Thermal smearing of the gap structure is observed below Tc. Temperature dependence of the gap parameter is consistent with BCS. Even above Tc the conductance curve is not flat.

Here we report the anomalous electro-caloric effect (ECE) observed in lead-free SrxBa(1−x)Nb2O6 (, 0.61 and 0.75) ferroelectric single crystals. Temperature-dependent hysteresis measurement revealed that the spontaneous polarization of SrxBa(1−x)Nb2O6 single crystals with all the compositions under investigation decreases with a decrease in the temperature below the temperature of the dielectric maxima . As a consequence, these crystals exhibited negative electro-caloric effect at lower temperature along with the usual positive ECE above . The EC coefficient obtained near is 0.21, 0.43 and 0.28 K mm/kV for , 0.61 and 0.75 samples, respectively. The maximum values of in the negative ECE region are −1.4, −0.81 and for 50SBN, 61SBN and 75SBN, respectively.

To clarify whether the thermal diffusivity along the X-axis of a periodically poled Mg 1-mol %-doped near-stoichiometric LiTaO3 (PPMgSLT) frequency-conversion device is the same as that of bulk-MgSLT crystal, we measured the thermal diffusivity along the X-axis (the direction perpendicular to the domain-wall) of a PPMgSLT device with a domain-inverted period of 8.0 µm by using a modified AC calorimetric method (laser-heating Ångström method) at room temperature. We found that the thermal diffusivity [(1.98±0.06)×10-6 m2/s] was almost the same as that of bulk-MgSLT crystal [(2.09±0.04)×10-6 m2/s]. This means that domain-walls are not phonon scattering centers with respect to thermal diffusivity and that domain-walls do not affect thermal diffusivity at room temperature. Consequently, the thermal diffusivity of bulk-MgSLT crystal is acceptable for PPMgSLT devices.

We investigated the effect of Ga doping on optical damage (photorefractive damage) in near-stoichiometric LiNbO3 (SLN) crystals. SLN crystals doped with Ga (Ga:SLN) were grown from a Li-rich solution by a top-seeded solution growth method. The optical damage resistance of the crystals was investigated at 532 nm. Crystals with a Ga doping concentration of at least 0.49 mol % showed no optical damage. The Ga doping shifted the OH- absorption peak position from 2.88 to 2.85 µm for crystals with a 0.49 mol % concentration. This concentration is lower than the 1 mol % Mg doping concentration required to suppress optical damage in SLN crystals. This attractive optical damage resistance characteristic makes Ga:SLN crystals another candidate as an optical damage resistant material, in addition to Sc-doped SLN crystals, for applications such as electrooptic devices and quasi-phase-matched frequency converters.

Sr0.61Ba0.39Nb2O6 crystals grown by a modified double-crucible Stepanov technique have coercive fields independent of thickness. The coercive field is about 250 V/mm as measured from the ferroelectric hysteresis loop. However, the coercive field is found to depend strongly on the ramp rate. Dielectric measurements revealed a diffused phase transition at about 352 K and a Curie constant of about 4.5 ×105 K.

Near-stoichiometric LiNbO3 (SLN) crystals doped with Sc (Sc:SLN) were grown from Li-rich solutions through a top-seeded solution growth (TSSG) method using resistance heating equipment. The optical damage resistance of the Sc:SLN crystals was investigated at a wavelength of 532 nm. The Sc:SLN crystals doped with more than 0.4 mol% Sc doping concentration showed no optical damage. The OH absorption peak for the Sc:SLN crystals shifted from 2.88 µm to 2.85 µm at 0.4 mol% Sc. This critical Sc doping concentration in the SLN crystal was one-fifth that in a congruent melt composition LN (CLN) crystal which required at least 2 mol% Sc (1 mol% Sc2O3) to suppress optical damage. The 0.4 mol% Sc doping required to suppress optical damage in the SLN crystal was also low compared to the 1 mol% Mg doping required for the same purpose. Hence, the Sc:SLN crystal is a more promising material with respect to resisting optical damage when applied to, for example, electrooptic devices.

Near-stoichiometric LiNbO3:Ce,Mn exhibited a reversible photochromic effect at room temperature. Irradiation with ultraviolet (UV) light enhanced a visible absorption band, and the photorefractive sensitivity to 532 nm-green recording light was greatly improved after UV irradiation. Hologram multiplexing was performed with a continuous-wave 532 nm-green laser by the angle-multiplexing method without and with UV pre-exposure. An M/# of ∼5 was obtained in a crystal of 2.55 mm-thickness in the absence of UV pre-exposure. In multiplexing after UV pre-exposure, however, the variable sensitivity and erasure-time constant made it very difficult to achieve a multiple hologram storage with nearly equivalent diffraction efficiency.

A cerium-substituted yttrium iron garnet (Y3-x Ce x Fe5O12) single crystal was grown by the traveling solvent floating zone (TSFZ) method in an oxygen environment. Using a Fe- and Ce-rich solvent, high quality single crystals with smooth and lustrous surface were grown at a rate of 1.0 mm/h. The segregation coefficient of Ce was calculated approximately as 0.2 from the compositional profile in the grown crystals measured by electron probe X-ray microanalyzer (EPMA). The optical absorption coefficient and the Faraday rotation angle of Y2.82Ce0.18Fe5O12 at 1550 nm wavelength were 0.12 cm-1 and -740 deg/cm, respectively. The figure of merit of a Faraday rotator was 1423 deg/dB. The absorption loss and sensitivity of the same Y2.82Ce0.18Fe5O12 (d=0.6 mm) for the magnetic field sensor were 0.03 dB and 0.1%/Oe, respectively, at 1550 nm wavelength. These results suggest that cerium-substituted yttrium iron garnet is a high performance material for the Faraday rotator at 1550 nm wavelength.

Crystal structures of Pb-doped BSCO superconductors, Bi2.1-x Pb x Sr1.9CuO y with x=0 to 0.3, are examined by transmission electron microscopy. Compounds with x from 0.05 to 0.2 exhibit satellite reflections in b *-c * electron diffraction patterns in a different manner from the x=0 compound, indicating formation of modulated structures similar to those observed in Pb-doped BSCCO superconductors. Modulation periodicity increases with increase of Pb content x. The compound with x=0.3, however, shows no satellite reflections suggesting the absence of modulation at high Pb content.

The behavior of YBa2Cu3O x crystals upon annealing was investigated by a polarizing microscope. Gradual transformation between the orthorhombic and tetragonal phases was observed in situ on heating and on cooling in oxygen atmosphere. An obvious change was recognized between twin domain structures before and after annealing. It is indicated that there is a possibility of reducing the number of twin domains in the crystal.

In order to identify the superconducting phase in the Bi-Ca-Sr-Cu-O system, phase search experiments were performed. The results of power X-ray study, EPMA study, specific gravity measurements and oxygen analysis revealed that the compound having the composition Bi2(Ca, Sr)3Cu2O9 or Bi2(Ca, Sr)3-Δ x Cu2O9-Δ y is responsible for the high-T c superconductivity. Two possible structure models, which are closely related to the structure of the bismuth titanate Bi4Ti3O12, are proposed for this compound.

Three nonsuperconducting phases (B to D) in a Bi-Sr-Cu-O system have long-period structures closely related to that of the superconducting phase A, Bi2Sr2CuO y . In phase B, the long periodicity is caused by the displacements of the (BiO)2 planes along the c axis. In both phases C and D, it is due to the formations of thin vertical planes of different local structures and compositions. These planes are straight and repeat regularly to form a commensurate long-period structure in phase C, while they repeat irregularly to form an incommensurate structure with wavy lattice planes in phase D.

The structure parameters of a superconductor with the nominal composition Ba1.8Nd1.2Cu3O7-y were refined by the Rietveld analysis of TOF neutron powder diffraction data. This material is tetragonal with lattice constants a=3.8919 Å and c=11.6811 Å and isomorphous with Ba1.5La1.5Cu3O7±y with an oxygen-deficient triperovskite structure. An oxygen site at (0, 1/2, 0) is 49% occupied, the Nd3+ ion at (1/2, 1/2, 1/2) is coordinated to eight oxide ions, and a metal site at (1/2, 1/2, 0.1842) is 90% and 10% occupied by Ba2+ and Nd3+ ions, respectively.

The powder X-ray diffraction pattern of superconductor Bi2(Sr, Ca)3-x Cu2O y was assigned taking into account the satellite reflections arising from an incommensurate modulated structure. All reflections are indexable with h a*+k b*+l c*+m k, provided that the wave vector k of the modulated structure is b*/4.8. The result shows that many satellites can be observed and some satellite intensities are strong.

A solid solution system Nd1+2x Ba2(1-x)Cu3O y (0≤x≤0.4) was investigated through its magnetic susceptibility and electrical resistivity. In the system, trivalent Nd ions partly occupy the Ba2+ sites of the structure, depending on x. Superconductivity was observed in the range of x=0∼0.16 and the transition temperature decreased steadily with increasing x. The resistivity in a normal state varied from metallic to semiconductive in character with an increment of x. These phenomena are discussed from the viewpoint of how trivalent, magnetic Nd ions in the Ba-O layers affect superconductivity in the system.

A superconducting material with a T c∼110 K in the Bi-Sr-Ca-Cu-O system is liable to contain stacking faults as suggested by the broadened diffraction. The diffraction intensity is simulated by applying the matrix method based on assumed models of stacking faults. The calculated intensity distributions explain the features of the observed powder X-ray diffraction patterns of the high-T c specimens.

The number of electrons around Cu atoms of tetragonal YBa2Cu2.933O6.38 gas been calculated from the charge integrations by direct Fourier summations of X-ray diffraction data. The atomic charges estimated from the total number of electrons belonging to the Cu1 and Cu2 atoms are +0.98(8) e and +1.78(7) e, suggesting univalent (3d 10) and divalent (3d 9) ionic states, respectively. The respective ionic states accord with the observations of the spherical electron distribution (Cu1) and of localized electron (Cu2).

Single crystals of Ba2YCu3O x were grown from nonstoichiometric melts in the system Ba-Y-Cu-O. From the melt having the composition BaO:YO1.5:CuO = 12:1:26, single crystals in rectangular form with the size up to 0.5 mm were grown together with thin plates up to 2 mm with the thickness of about 30 µm. They have tetragonal symmetry with the cell parameters a = 3.862 Å and c = 11.80 Å. The measurement of the electrical resistivity revealed that their resistivity was about 4 Ωcm at room temperature and that the superconducting transition did not occur down to 65 K.

The structure of the 20 K superconductor Bi2Sr2CuO y is examined by high-resolution transmission electron microscopy. A strongly modulated structure due to the periodic lattice distortions is observed. The unit cell is B-centered monoclinic with a m=0.54, b m=2.6, c m=2.8 nm and α=116°, where b m is incommensurate with the tetragonal subcell. The pseudo-orthorhombic setting of the unit cell, where A=a m=0.54, B=b m=2.6 and C=2c m cos α=5.0 nm, reported previously [Matsui et al.: Jpn. J. Appl. Phys. 27 (1988) L827], is considered convenient to compare the superstructure with the orthorhombic one of the 80 K superconductor Bi2Sr2CaCu2O y .

Four compounds within a range of solid solution Ba2-x Nd1+x Cu3O y (where x ranges from 0 to 0.8) are examined by transmission electron microscopy. Ba2NdCu3O y , with T c= 83 K, has an ortho rhombic structure with twinned microstructure, similar to that of Ba2YCu3O y with T c= 90 K. Ba1.8Nd1.2Cu3O y , with T c= 45 K, and Ba1.5Nd1.5Cu3O y (nonsuperconductor) are both tetragonal, but the latter has a domain structure where the c axes of neighboring domains are perpendicular to each other. Ba1.2Nd1.8Cu3O y (nonsuperconductor) has a superstructure with A s=2a, B s=b and C s=2c. Two possible models of the superstructure are proposed.

Twinned structure with twin plane (510) and with the composition plane (001) is observed in a high-T c Bi-Sr-Ca-Cu-O superconductor which is orthorhombic with a=0.54, b=2.7 and c=3.08 nm. Directions of “Bi-concentrated bands” in both twin individuals are perpendicular to each other. Local intergrowths of perovskite-related layers with 1.8 and 2.1 nm thickness are observed among the major layers of 1.5 nm. The material includes small amounts of crystal with c=3.6 nm, which may be responsible for the superconductivity at 105 K, as already suggested by Muromachi et al. (Jpn. J. Appl. Phys. 27 (1988) L556).

A Raman scattering study was performed in a variety of single crystals of both tetragonal and orthorhombic Ba2YCu3O y structures at room temperature. It is found that Raman spectra observed in the tetragonal crystal are much different from those in the orthorhombic one. Three modes with 500 cm-1 580 cm-1 and 637 cm-1 in energy in the orthorhombic crystal are tentatively assigned to be the copper-oxygen vibrational modes. The 500 cm-1 mode is assigned as the oxygen-stretching mode in Cu-O-Cu bond along the c-axis and its frequency is found to shift to 470 cm-1 in the tetragonal crystal.

Crystal structure of tetragonal YBa2Cu2.93O6.38 has been determined by the single-crystal X-ray diffraction method. The space group is P4/mmm with lattice constants: a = 3.860(1) Å, c = 11.813(4) Å, and V = 176.05(7) Å3. The structure refinement has been successfully carried out with the final R value of 0.019(Rw=0.020). A difference-Fourier map reveals the existence of localized d-electrons around Cu2 atoms in the unit cell, although the electrons of Cul atoms have a spherical distribution.

Raman scattering is measured in the a b plane of the Bi2.2Sr1.8CaCu2O y superconductor. It is found that the electronic Raman scattering appears as a continuum spectrum in both polarized and depolarized scattering and the electronic continuum interferes with some phonon lines. Below T c, the electronic continuum redistributes due to a gap formation and a broad peak appears at about 400 cm-1, which is larger than the expected value 2Δ=209 cm-1 of the BCS-theory.

The Nd1+x Ba2-x Cu3O y system and its superconductivity were studied. This system forms a solid solution within the x range of 0.00 to 0.80. At room temperature, it has orthorhombic symmetry for x ranging from 0.00 to 0.14 and tetragonal symmetry for x not less than 0.20. All specimens at 900°C in air have tetragonal symmetry. It is a superconductor in the region of x less than 0.50. The superconducting onset temperature decreases from 93.5 to 40.0 K with increasing x. In comparison with the superconductivity of the La1+x Ba2-x Cu3O y system, there appears to be little influence of the magnetic ion Nd3+ on the T c in the Nd1+x Ba2-x Cu3O y system.

The high-T c superconductor Bi2(Sr, Ca)4Cu3O y with T c=110 K is examined by high resolution electron microscopy. Most of the perovskite-related layers are composed of three CuO2 and four (Sr, Ca)O layers, separating two Bi2O2 layers by 1.8 nm. Intergrowths of perovskite-related layers containing two, four and five CuO2 layers are observed, where the Bi2O2 layers are separated by 1.5, 2.1 and 2.4 nm, respectively. The structural modulation, similar to that reported in the 80 K low-T c superconductor Bi2(Sr, Ca)3Cu2O y (Y. Matsui et al.: Jpn. J. Appl. Phys. 27 (1988) L372), is also observed.