Rock-salt Block Research Articles

Combined effect of charge carriers and crystal structure on high-Tc superconductivity in codoped Y1-xCaxBa2-yLayCu3Oz

Polycrystalline samples of Y1-xCaxBa2-yLayCu3Oz cuprate superconductors with both x and y ranging from 0 to 0.5 were investigated. The combinative energy between the perovskite block and the rock-salt block in this codoped system was calculated according to a previously proposed “block model”. By defining a new parameter γ describing the combined effects of the combinative energy (lattice degree of freedom) and the charge carrier density (charge degree of freedom), it is revealed that the tendency of γ changing with doping is well consistent with that of the superconducting transition temperature (Tc) over the whole doping range, suggesting the important roles of both the lattice and charge degrees of freedom in influencing the unconventional superconductivity.

Rock splitting techniques for reducing undesirable cracks and fissures in rock salt blocks

Massive deposits of rock salt are mined in the Salt Range area of Pakistan. The main export products of rock salt include salt lamps, blocks, and tiles, while local consumption includes the chemical industry and domestic use. The profitable production of salt for value addition depends on the quality, size, and shape of the block. Salt processing for value addition is easier when very few cracks are present in the blocks. The current salt mining practice involves drilling and blasting, which introduces undesired fractures in the material. This paper focuses on the extraction of rock salt blocks by applying conventional cuboid-shaped block mining methods used in quarries. The techniques include wedges and feathers, expansion chemicals, and blasting with low-yield explosives. Experimental work involved both laboratory-scale and in-situ field testing. Laboratory experiments assisted with the determination of splitting force, load-deformation curves, and other rock mechanics parameters. Regression analysis proposes a relationship for the estimation of radial strain from the load in the case of the wedges and feathers method. The splitting force obtained from the laboratory tests was used to confirm the accuracy of the already published empirical relationship. The results of the laboratory as well as in-situ tests showed that the wedges and feathers technique is the most suitable method for mining rock salt blocks of the desired size, shape, while minimizing cracking.

Crystal structure and electronic property modification of Ca2RuO4 thin films via fluorine doping

Layered ruthenium oxyfluorides have various crystal structures and Ru oxidation states and exhibit unique physical properties. While various layered ruthenates have reportedly been topochemically fluorinated with Sr as $A$ sites, investigation of the fluorination of layered ruthenates containing smaller Ca ions is lacking. In this paper, we fabricated phase-pure and single-crystalline thin films of ${\mathrm{Ca}}_{2}{\mathrm{RuO}}_{2.5}{\mathrm{F}}_{2}$ on ${\mathrm{LaSrAlO}}_{4}$ (001) substrates via topochemical fluorination of the ${\mathrm{Ca}}_{2}{\mathrm{RuO}}_{4}$ precursor using polyvinylidene fluoride. The obtained fluorinated thin films had a chemical composition of ${\mathrm{Ca}}_{2}{\mathrm{RuO}}_{2.5}{\mathrm{F}}_{2}$ with the ${\mathrm{Ru}}^{3+}$ state, as determined by energy-dispersive x-ray spectroscopy and x-ray photoemission spectroscopy, whereas the film prepared via ${\mathrm{Sr}}_{2}{\mathrm{Ru}}^{4+}{\mathrm{O}}_{4}$ fluorination had a composition of ${\mathrm{Sr}}_{2}{\mathrm{Ru}}^{4+}{\mathrm{O}}_{3}{\mathrm{F}}_{2}$. Scanning transmission electron microscopy revealed that ${\mathrm{Ca}}_{2}{\mathrm{RuO}}_{2.5}{\mathrm{F}}_{2}$ has only 1 ${\mathrm{F}}^{\ensuremath{-}}$ site in CaO rock-salt blocks, whereas ${\mathrm{Sr}}_{2}{\mathrm{RuO}}_{3}{\mathrm{F}}_{2}$ has two inequivalent ${\mathrm{F}}^{\ensuremath{-}}$ sites in the SrO layers. The ${\mathrm{Ca}}_{2}{\mathrm{RuO}}_{2.5}{\mathrm{F}}_{2}$ film was insulating, with a resistivity (\ensuremath{\rho}) of $8.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}$ at 300 K. Moreover, the temperature behavior of \ensuremath{\rho} was well described by the two-dimensional variable range hopping model. These results demonstrate that local distortion is an important factor that governs the topochemical fluorination of ruthenates and affects the crystal and electronic structures of the reactants.

K2NiF4 type oxides, Ln2-xSrxNiO4+δ (Ln = La and Pr; x = 0–1.4) as an oxygen electrocatalyst for aqueous lithium–oxygen rechargeable batteries

The structural and electrochemical characteristics of the Ln2-xSrxNiO4+δ (Ln = La and Pr; x = 0–1.4) system were investigated to clarify the relationship between the electrocatalytic activity and various characteristics such as the structure, composition, electrical conductivity, and oxygen content. Rietveld analysis of the powder X-ray diffraction (XRD) data showed that the tetragonal distortion of the NiO6 octahedra decreased monotonically with an increase of x, while the Ln (Sr)–O (//c-axis) in the rock-salt block was expanded with an increase in x, although the tetragonality, c/a showed a maximum at x = 0.6. Cyclic voltammetry (CV) measurements showed that the activity for the oxygen evolution reaction (OER) increased with x, while that of the oxygen reduction reaction (ORR) was independent of x. The characteristic peak due to oxygen insertion into the lattice was observed at ca. 1.45 V vs. RHE, the intensity of which increased with the Sr content, which reflects the increase in the internal chemical diffusion of oxygen species. X-ray photoelectron spectroscopy (XPS) measurements for the constituent elements confirmed the presence of OH− groups inside the catalyst particles, especially in the Sr-rich region. It is suggested that the reversible intercalation ability of the OH− group into the rock-salt layer in the Ruddlesden-Popper (RP) phase (An+1BnO3n+1) contributes significantly to the improvement of the OER activity.

Protonic transport in the new phases BaLaIn0.9M0.1O4.05 (M=Ti, Zr) with Ruddlesden-Popper structure

The new proton-conducting phases BaLaIn0.9M0.1O4.05 (M = Ti, Zr) with Ruddlesden-Popper structure were obtained. The substitution of In3+ ions by the Ti4+ and Zr4+ ions leads to the expansion of the ab plane due to the incorporation of the oxygen interstitials in the La–O rock-salt blocks. It was established that all investigated samples were capable for the water uptake from the gas phase due to the presence in the structure of La–O blocks. The degree of hydration increased with an increase in the size of the salt blocks. It was proved that doping led to the increase in the oxygen ionic conductivity due to the formation of interstitial oxygen. The conductivity values for doped sample BaLa0.9M0.1InO3.95 were higher than for undoped composition BaLaInO4 by ~1 order of magnitude. The new phases BaLaIn0.9M0.1O4.05 (M = Ti, Zr) demonstrate the predominant protonic conductivity at Т<450 °C and pH2O = 2·10−2 atm.

Block Extraction of Himalayan Rock Salt by Applying Conventional Dimension Stone Quarrying Techniques

A salt block is a regular prism of rock salt containing least undesirable cracks which is mainly used for carving artifacts especially salt lamps, tiles and other products. This research work is focused on the comparison of three common and simple dimension stone quarrying techniques including wedges and feathers, expansive cement, and controlled blasting methods for the extraction of rock salt block. The selected techniques were applied at the underground working face of Khewra Salt Mines (Punjab, Pakistan) to extract representative blocks in accordance with a predefined field experimental program. In order to find out the most suitable block extraction technique in terms of the quality of excavated salt blocks, physical and mechanical rock property tests were performed comprising of core recovery, uniaxial compressive strength, Brazilian tensile strength, dynamic Young’s modulus, quality and P-wave velocity. This paper statistically confirms that the rock salt blocks excavated by using wedges and feathers method have higher quality in comparison to the blocks obtained by expansive cement and controlled blasting techniques. Further the results of overall technique wise comparison are also discussed.

平面四配位を有する酸化物における圧力誘起相転移

A spin state transition in a square planar coordinated iron was found in SrFeO2 and Sr3Fe2O5 under high pressure. This transition occurs as a consequence of enhanced Fe-Fe direct interactions between adjacent face-to-face FeO4 square planar units. We also found a pressure-induced structural transition in Sr3Fe2O5, which is viewed as a B1（NaCl structure） to B2（CsCl structure） structural transition. Such a B1-B2 structural transition generally occurs in intergrowth system consisting of rock-salt blocks and square-planar blocks, as found in A2MO3 （A＝Ca, Sr; M＝Cu, Pd）. An empirical relation between the structural transition pressure Ps and the ionic radius for the binary system holds well for the intergrowth structure, which indicates that the square-planar block is highly compressible along the out-of-plane direction.

Outstanding Atomic Order in Ruddlesden–Popper Oxide Microcrystals

Ruddlesden–Popper’s manganates, An+1MnnO3n+1, built from the ordered intergrowth between one rock-salt and n perovskite blocks, display a wide variety of functionalities related to their physical-chemistry properties which can be in principle tuned by chemical modifications. Nevertheless, the poor thermodynamic stability of the high members constitutes an inherent impediment, limiting the development of new functionalities in this family. Actually, for n ≥ 2, defects involving disordered intergrowths between perovskite and rock-salt blocks are always present avoiding the correct characterization of their properties. For that purpose, the use of sophisticated and expensive physical methods is required. In this article, the stabilization, following a chemical strategy, of micrometric La0.5Ca2.5Mn2O7 crystalline particles exhibiting a well ordered distribution of two perovskite and one rock-salt block, according to an ideal n = 2 unit cell, is reported. This apparently long-range structural ordering is linke...

Misfit-layered Bi1.85 Sr2 Co1.85 O7.7-δ for the hydrogen evolution reaction: beyond van der Waals heterostructures.

Recent research on stable 2D nanomaterials has led to the discovery of new materials for energy-conversion and energy-storage applications. A class of layered heterostructures known as misfit-layered chalcogenides consists of well-defined atomic layers and has previously been applied as thermoelectric materials for use as high-temperature thermoelectric batteries. The performance of such misfit-layered chalcogenides in electrochemical applications, specifically the hydrogen evolution reaction, is currently unexplored. Herein, a misfit-layered chalcogenide consisting of CoO2 layers interleaved with an SrO-BiO-BiO-SrO rock-salt block and having the formula Bi1.85 Sr2 Co1.85 O7.7-δ is synthesized and examined for its structural and electrochemical properties. The hydrogen-evolution performance of misfit-layered Bi1.85 Sr2 Co1.85 O7.7-δ , which has an overpotential of 589 mV and a Tafel slope of 51 mV per decade, demonstrates the promising potential of misfit-layered chalcogenides as electrocatalysts instead of classical carbon.

Oxide ion conductivity in defect perovskite, Pr&lt;sub&gt;2&lt;/sub&gt;NiO&lt;sub&gt;4&lt;/sub&gt; and its application for solid oxide fuel cells

Oxide ion conductivity in defect perovskite, mainly Pr2NiO4 with K2NiF4 structure, was studied in details. Defect perovskite oxide consists of perovskite block connected series to oxygen deficient block and although it is known that oxygen deficient block traps mobile oxide ion in lattice, interstitial oxygen introduced at rock salt block in Pr2NiO4 shows high mobility resulting in the high oxide ion conductivity. Oxide ion conductivity is much increased by doping Cu and Ga for Ni site and Pr deficient. The observed oxide ion conductivity was high like log (σ/Scm−1) = −0.25 at 1173 K. Conducting property of Pr1.91Ni0.75Cu0.21Ga0.05O4(PNCG)/Ce0.8Sm0.2O2(SDC) nano laminated film was further studied and the conductivity was much increased by formation of residual strain and the ion blocking method shows the transport number of the laminated film is almost unity and so high conductivity of PNCG/SDC laminated film could be assigned to pure oxide ion. Application of PNCG for anode of SOFC was further studied and it was found that surface activity of Pr2NiO4 doped with Cu and Ni shows high and so superior cathodic property was achieved at low temperature by mixing Pr2NiO4 with SDC. The maximum power density of the cell using LaGaO3 thin film electrolyte was achieved at 0.12 W/cm2 at 673 K.

Thermoelectric misfit-layered cobalt oxides with interlayers of hydroxide and peroxide species

Among the thermoelectric misfit-layered cobalt oxides, [MmA2Om+2]qCoO2, the parent m=0 phases exhibit divergent chemical features but are less understood than the more common m>0 members of the series. Here we synthesize Sr-for-Ca substituted [(Ca1−xSrx)z(O,OH)2]qCoO2 zero phases up to x=0.2 through low-temperature hydrothermal conversion of precursor powders of the m=1 misfit system, [Co(Ca1−xSrx)2O3]qCoO2. In the zero-phase [(Ca1−xSrx)z(O,OH)2]qCoO2 system, as the Sr content x increases the lattice expands anisotropically along the c axis such that the ab-plane dimension and the misfit parameter q remain essentially constant. X-ray absorption spectroscopy data suggest the presence of peroxide-type oxygen species in the (Ca1−xSrx)z(O,OH)2 rock-salt block and together with infrared spectroscopy, thermogravimetric and low-temperature resistivity and thermopower measurements evidence that the isovalent Sr-for-Ca substitution controls the balance between the peroxide and hydroxide species in the (Ca1−xSrx)z(O,OH)2 block but leaves the valence of Co essentially intact in the CoO2 block. The higher electrical conductivity of the Sr-substituted phases is explained as a consequence of increased carrier mobility.

FIXED TRIANGLE IN Bi2-XPbXSr2CaCu2O8+Y AND Bi2-XPbXSr2Ca2Cu3O10+Y SYSTEMS

The structural characteristics of Bi 2-x Pb x Sr 2 CaCu 2 O 8+y( Bi -2212) and Bi 2-x Pb x Sr 2 Ca 2 Cu 3 O 10+y( Bi -2223) with x changing from 0 to 0.8 were studied by X-ray diffraction and Rietveld refinement. By careful calculation of chemical bond lengths and angles, it is found that there exists a fixed triangle on the Cu–O planes in the two systems, and then makes the Cu–O planes stable. The fluctuations of this fixed triangle were investigated, and it is found that there is a close relationship between it and Tc's. In addition, we discussed the origin of this special local structure. It may be caused by the interaction between the perovskite block and the rock salt block in a unit cell, which may play an important role in the mechanism of high temperature superconductivity.

Expanding the Ruddlesden–Popper Manganite Family: The n = 3 La3.2Ba0.8Mn3O10 Member

La(3.2)Ba(0.8)Mn(3)O(10), a representative of the rare n = 3 members of the Ruddlesden-Popper manganites A(n+1)Mn(n)O(3n+1), was synthesized in an evacuated sealed silica tube. Its crystal structure was refined from a combination of powder X-ray diffraction (PXD) and precession electron diffraction (PED) data, with the rotations of the MnO(6) octahedra described within the symmetry-adapted mode approach (space group Cccm, a = 29.068(1) Å, b = 5.5504(5) Å, c = 5.5412(5) Å; PXD R(F) = 0.053, R(P) = 0.026; PED R(F) = 0.248). The perovskite block in La(3.2)Ba(0.8)Mn(3)O(10) features an octahedral tilting distortion with out-of-phase rotations of the MnO(6) octahedra according to the (Φ,Φ,0)(Φ,Φ,0) mode, observed for the first time in the n = 3 Ruddlesden-Popper structures. The MnO(6) octahedra demonstrate a noticeable deformation with the elongation of two apical Mn-O bonds due to the Jahn-Teller effect in the Mn(3+) cations. The relationships between the octahedral tilting distortion, the ionic radii of the cations at the A- and B-positions, and the mismatch between the perovskite and rock-salt blocks of the Ruddlesden-Popper structure are discussed. At low temperatures, La(3.2)Ba(0.8)Mn(3)O(10) reveals a sizable remnant magnetization of about 1.3 μ(B)/Mn at 2 K, and shows signatures of spin freezing below 150 K.

Magnetic and magnetotransport properties of misfit cobaltate Ca3Co3.93O9+δ

Samples of Ca3Co3.93O9+δ, prepared by classical ceramic route (CCR) and spark plasma sintering (SPS), were characterized by means of magnetic, electrical, and thermal experiments in a broad temperature range. The low temperature specific heat measured down to 0.3 K, reveals two important electronic contributions: the first one, dominated by magnetic excitations, that can be suppressed by an external magnetic field, and the second, due to band-like carriers, characterized by γ ∼ 50 mJ mol−1 K−1 for both samples. The ferrimagnetism, associated with the long-range magnetic order of IS Co3+ species in rock-salt blocks detected below TF ∼15 K in the CCR samples, is absent in the SPS samples. Similarly, the specific heat peaks detected for the CCR sample at 410 and 840 K are not reproduced in the case of the SPS sample. In both samples the low temperature thermoelectric power is quantitatively explained by supposing the strongly correlated carriers are carrying the spin entropy. The lower hole concentration in the SPS than in the CCR sample is likely responsible for its higher thermopower, namely, at high temperatures where the configuration entropy of hopping carriers dominates.

B1-to-B2 Structural Transitions in Rock Salt Intergrowth Structures

The rock salt (B1) structure of binary oxides or chalcogenides transforms to the CsCl (B2) structure under high pressure, with critical pressures P(s) depending on the cation to anion size ratio (R(c)/R(a)). We investigated structural changes of A(2)MO(3) (A = Sr, Ca; M = Cu, Pd) comprising alternate 7-fold B1 AO blocks and corner-shared MO(2) square-planar chains under pressure. All of the examined compounds exhibit a structural transition at P(s) = 29-41 GPa involving a change in the A-site geometry to an 8-fold B2 coordination. This observation demonstrates, together with the high pressure study on the structurally related Sr(3)Fe(2)O(5), that the B1-to-B2 transition generally occurs in these intergrowth structures. An empirical relation of P(s) and the R(c)/R(a) ratio for the binary system holds well for the intergrowth structure also, which means that P(s) is predominantly determined by the rock salt blocks. However, a large deviation from the relation is found in LaSrNiO(3.4), where oxygen atoms partially occupy the apical site of the MO(4) square plane. We predict furthermore the occurrence of the same structural transition for Ruddlesden-Popper-type layered perovskite oxides (AO)(AMO(3))(n), under higher pressures. For investigating the effect on the physical properties, an electrical resistivity of Sr(2)CuO(3) is studied.

Mixed Conductivity, Nonstoichiometric Oxygen, and Oxygen Permeation Properties in Co-Doped Sr3Ti2O7−δ

Electrical conductivity and oxygen permeation rates in Co-doped Sr(3)Ti(2)O(7-δ) with Ruddesden-Popper type structures were investigated. The effects of metal dopants (M) in the Ti site of Sr(3)Ti(2)(M)O(7-δ) on the mixed conductivity were also studied. Doping of Sr(3)Ti(2)O(7-δ) with Co was found to be effective for improving the electrical conductivity as well as the oxygen permeation rate, which could be assigned to the increased oxygen vacancy concentration by doping Co(3+) into Ti(4+) sites. The nonstoichiometric oxygen of these oxides was measured by using a thermal gravimetric method. The creation of oxygen vacancies, which is compensated with Co(3+) doping, leads to higher oxide ion conductivity. The oxygen permeation rate monotonously increased with increasing amounts of Co in the Ti site. Sr(3)Ti(0.8)Co(1.2)O(7-δ) exhibited high oxide ion conductivity and a large oxygen permeation rate. The highest oxygen permeation rate achieved a value of 2.02 cc min(-1) cm(-2) at 1273 K for Sr(3)Ti(0.8)Co(1.2)O(7-δ). Neutron diffraction analysis and redox titration suggests that the oxygen diffusion occurs through oxygen vacancies in the perovskite block, but not through excess oxygen in the rock salt block.

Relation of Structure and Superconductivity in Self-compensated Y1−x Ca x Ba2Cu3−x Al x O z System

The co-doped compounds of Y1−xCaxBa2Cu3−xAlxOz, with x from 0.1 to 0.4, were synthesized through a solid-state reaction method. Structural and superconducting properties have been investigated by X-ray diffraction, Rietveld refinement, and DC magnetization measurement. The lattice constant a decreases while b increases with the addition of x. The difference between a and b diminishes gradually. Careful study of the crystalline structure shows that the critical temperature (Tc) changes monotonically with some local structural parameters, such as the difference between Ba and Cu(2) atoms’ Z coordinates, the bond length of Cu(2)–O(4), and the bond angle of Cu(2)–O(2)–Cu(2), which are all closely related to the interaction between the perovskite block and the rock salt block in the unit cell. The results indicated that the influence of the crystalline structure on superconductivity is important and independent of the carrier concentration.

The fixed triangle chemical bond and its effect in the Y1−xCaxBa2−yLayCu3Oz system from underdoped to overdoped

Samples of Y1−xCaxBa2−yLayCu3Oz (YCBLCO) were synthesized by the standard solid-state reaction with both x and y taking values from 0 to 0.5. Structural and superconducting properties have been investigated by x-ray diffraction, Rietveld refinement and dc magnetization measurement. The three-dimensional phase diagram in the YCBLCO system is obtained, describing the dependence of Tc on the content of two dopants simultaneously. By careful study of the chemical bond lengths related to the Cu(2)O2 plane and the Cu(1)–O chain, it is found that Tc has opposite dependences on the bond lengths of Cu(1)–O(4) or Cu(2)–O(4) in the underdoped (x<y) and overdoped (x>y) regions. In addition, calculation of the bond angles for the optimal-doped samples indicates that Tc is closely related to four pairs of bond angles, all of which characterize the curvature of the CuO2 plane. It is demonstrated that the interaction between the perovskite block and the rock salt block in a unit cell has a close relationship with the superconductivity. The calculation of bond lengths and angles indicates that Cu(2), O(2) and O(3) on the CuO2 plane form a ‘fixed triangle’, independent of the doping level in the system. It is suggested that the collective behavior of the fixed angle might result in a particular phonon mode, which may induce a special kind of electron–phonon coupling, different from that appearing in conventional superconductors. This may be of great importance for uncovering the elusive mechanism of high-temperature superconductivity.

Relationship among thermal anomalies, superconductivity and structural blocks indifferent-metal-site-doped YBCO

Three series of polycrystalline samples ofYBa2Cu3−xNixOy(YBCNO),Y1−xPrxBa2Cu3Oy (YPrBCO)and YBa2−xLaxCu3Oy (YBLCO) (x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, respectively), synthesized by a solid state reaction technique, werecharacterized by thermogravimetry, differential scanning calorimetry, DC magnetizationmeasurement, temperature dependent x-ray diffraction and Rietveld refinement. To ourknowledge this is the first systematic report of two phase transitions at about 400 and850 °C before melting. By careful measurements it was seen that the amountsof the percentage weight loss and the DSC changes, along withTc,decrease with increasing dopant. Combining the theory of oxygen diffusion with the block model inYBCO, the mechanism of the phase transitions can be explained as follows: the phase transition at400 °C comes directly from O(1) in the rock salt block, while the phase transition at850 °C is related to the perovskite block. The calculation of the combinative energybetween the two structural rock salt and perovskite blocks shows that,with increasing dopant, the higher the combinative energy the lower theTc, and vice versa. The results indicate that there exits a triangular relationship amongthermal anomalies, superconductivity and structural blocks in different-metal-site-dopedYBCO, which may be significant for understanding the mechanism of high-temperaturesuperconductivity.

Unknown phase transitions, superconductivity and structural blocks inYBa2Cu3−xNixO7−δ

Polycrystalline samples of YBa2Cu3−xNixO7−δ (x = 0,0.05, 0.10, 0.15, 0.20, and 0.25) (YBCNO) were investigated by means of differentialscanning calorimetry, thermogravimetry, temperature dependent x-ray diffraction,Rietveld refinement with the help of the bond valence sum method, magneticmoment–temperature measurement and combinative energy calculation between thetwo structural blocks, perovskite and rock salt. It was observed that there aretwo thermal anomalies of weight loss and heat flow change at about 400 and850 °C in each sample before melting. By careful measurement it was found that theweight loss and endothermal absorption, as well as the critical temperatureTc,decrease with the increase of dopant. Combining the theory of oxygen diffusion with the block modelin YBCO, the mechanism of the phase transitions can be explained as follows: the phase transitionat 400 °C comes directly from O(1) in the rock salt block, while the phase transition at850 °C corresponds to O(2) and O(3) in the Cu(2)–O plane. When a phase transitionoccurs, the oxygen at O(2) and O(3) sites is rearranged and a few oxygenatoms enter the O(1) site of the Cu(1)–O plane through the O(4) bridgeatoms, finally escaping from the crystal cell. Thus the phase transition at850 °C is related to the perovskite block. The calculation of the combinativeenergy between the rock salt and perovskite blocks shows that withincreasing Ni content, the higher the combinative energy and the lower theTc. The results indicate that there is a close relationship among thermal phasetransitions, superconductivity and structural blocks in YBCNO, which may besignificant for understanding the mechanism of high temperature superconductivity.