Effects of Cd-Substitution Site on the Electrical Conductivities in Pb(Ni1/3Nb2/3)O3-PbZrO3-PbTiO3 Ceramics

The effects of Cd²⁺ substitution for Pb²⁺ and Ni²⁺ ions (on the A-site and B-site of the ABO₃ perovskite structure, respectively) on the electrical conductivities in Pb(Ni_1/3-Nb_2/3)O₃-PbZrO₃-PbTiO₃ (PNN-PZ-PT) ceramics have been investigated. Generally, the compounds that contain PbO show p -type conductivity, because of PbO evaporation. Thus, the conductivities are known to be proportional to the PbO evaporation. However, PNN-PZ-PT ceramics exhibit a reciprocal relationship between the conductivities and the evaporation of PbO. Generally, no vacancy change is observed with the substitution of the same-charge valence ion. However, in the PNN-PZ-PT ceramic, lead vacancies could be created or annihilated by replacing Pb²⁺ and Ni²⁺ ions with Cd²⁺ ions, because of incomplete substitution. The electrical conductivities are influenced by this incomplete substitution.     

Properties of Sm2O3─Al2O3─SiO2 Glasses for In Vivo Applications

The compositional range for glass formation below 1600°C in the Sm₂O₃─Al₂O₃─SiO₂ system is (9–25)Sm₂O₃─(10–35)Al₂O₃─(40–75)SiO₂ (mol%). Selected properties of the Sm₂O₃─Al₂O₃─SiO₂ (SmAS) glasses were evaluated as a function of composition. The density, refractive index, microhardness, and thermal expansion coefficient increased as the Sm₂O₃ content increased from 9 to 25 mol%, the values exceeding those for fused silica. The dissolution rate in 1 N HCl and in deionized water increased with increasing Sm₂O₃ content and with increasing temperature to 70°C. The transformation temperature ( T _g ) and dilatometric softening temperature ( T _d ) of the SmAS glasses exceeded 800° and 850°C, respectively.     

Phase Equilibria in the System ZrO2─InO1.5

Phase equilibria in the system ZrO₂─InO_1.5 have been investigated in the temperature range from 800° to 1700°C Up to 4 mol%, InO_1.5 is soluble in t -ZrO₂ at 1500°C. The martensitic transformation temperature m → t of ZrO₂ containing InO_1.5 is compared with that of ZrO₂ solid solutions with various other trivalent ions with different ionic radii. The diffusionless c → t ' A phase transformation is discussed. Extended solid solubility from 12.4 ± 0.8 to 56.5 ± 3 mol% InO_1.5 is found at 1700°C in the cubic ZrO₂ phase. The eutectoid composition and temperature for the decomposition of c -ZrO₂ solid solution into t -ZrO₂+InO_1.5 solid solutions were determined. A maximum of about 1 mol% ZrO₂ is soluble in bcc InO_1.5 phase. Metastable supersaturation of ZrO₂ in bcc InO _1.5 and conditions for phase separation are discussed.     

Glass Formation in the System SiO2–PbO Containing Transition-Metal Oxides

Glass-forming regions, valence states, and viscosities in SiO₂–PbO systems containing various transition-metal oxides as a third component were investigated. The glasses were prepared by melting in an open atmosphere. The glass-forming regions ranged as follows: MnO≡ZnO > FeO_1.5>NiO. The ratios Fe²⁺/(Fe²⁺+ Fe³⁺) and Mn³⁺/ (Mn³⁺+ Mn²⁺) in the glasses were determined by chemical analysis. The Fe²⁺/ (Fe²⁺+ Fe³⁺) ratio in SiO₂–PbO–FeO_1.5 glasses ranged from 0.016 to 0.050. The Mn³⁺/ (Mn³⁺+ Mn²⁺) ratio in SiO₂–PbO–MnO glasses ranged from 0.056 to 0.30. The fraction of manganese (III) ions in the glasses varies considerably with the glass composition. The effects of transitionmetal oxides on the viscosity are discussed.     

Porous Glass-Ceramics with a Skeleton of the Fast-Lithium-Conducting Crystal Li1+xTi2−xAlx(PO4)3

Porous glass-ceramics with a skeleton of the fast-lithium-conducting crystal Li_{1+ x} Ti_{2− x} Al _x (PO₄)₃ (where x = 0.3–0.5) were prepared by crystallization of glasses in the Li₂O─CaO─TiO₂─Al₂O₃–P₂O₅ system and subsequent acid leaching of the resulting dense glass-ceramics composed of the interlocking of Li_{1+ x} Ti_{2− x} Al _x (PO₄)₃ and β-Ca₃(PO₄)₂ phases. The median pore diameter and surface area of the resulting porous Li_{1+ x} Ti_{2− x} Al _x (PO₄)₃ glass-ceramics were approximately 0.2 μm and 50 m²/g, respectively. The electrical conductivity of the porous glass-ceramics after heating in LiNO₃ aqueous solution was 8 × 10⁻⁵ S/cm at 300 K or 2 × 10⁻² S/cm at 600 K.     

Gamma-Induced Absorption Bands Associated with Tl+, Pb2+, or Bi3+ in Potassium Borate Glasses

Gamma irradiation of potassium borate glasses containing about 1.8 mole % Tl⁺, Pb²⁺, or Bi³⁺ resulted in two induced absorption bands which the authors call T and L bands. The T band was observed at about 1.1, 1.55, or 1.8 ev, and the L band was observed at about 1.8, 2.6, or 2.7 ev in alkali borate glasses containing Tl⁺, Pb²⁺, or Bi³⁺, respectively. The shifting of the band positions to higher energies was attributed to the increasing polarizing power of these ions as in the case of the F band induced in alkali halides. The effect of the addition of cerium on the intensity of the T and L bands induced in glasses containing lead or thallium and prepared under different melting conditions suggested strongly that these two bands are associated with electron trap centers near these ions.     

New Yellow Ceramic Pigment Based on Codoping Pyrochlore-type Y2Ti2O7 with V5+ and Ca2+

A new yellow pigment with the pyrochlore structure Ca_xY_{2− x} V _x Ti_{2− x} O₇ was prepared as a substitute for the decreasing variety of available yellow ceramic pigments due to the severe regulation of toxic lead and cadmium. The solubility limit of vanadium in this pigment was found to be 1.5 wt% as V₂O₅ or 0.13 as x in the above formula expression. Characterization of vanadium in the vanadium pyrochlore yellow pigment by electron spectroscopy for chemical analysis and electron spin resonance showed that the oxidation state of vanadium was V⁵⁺ and its yellow color mostly originated from V⁵⁺ substituted for Ti⁴⁺. Comparison of color characteristics of Ca_xY_{2− x} V _x Ti_{2− x} O₇ with those of commercial V–SnO₂ and V–ZrO₂ revealed that Ca _x Y_{2− x} V _x Ti₂₋O₇ had better color strength and brightness than the commercial pigments.     

Substitution of Bi and Nb Ions in Lead Zirconate-Titanate

Solid-state substitution of Bi and Nb ions in the perovskite crystal structure of Pb(Ti_0.47Zr_0.53)O₃ was investigated by sample weight changes at 1150°C in an "equilibrium" PbO atmosphere. A model is discussed that includes the effect of charge neutralization, requiring weight losses for A-site substitutions and weight gains for B-site substitutions. Experiments support the substitution of Bi as Bi³⁺ on the Pb²⁺ A site and Nb as Nb⁵⁺ on the (Ti,Zr)⁴⁺ B site of lead zirconate-titanate. For each mole of BiO_1.5 added to a specimen, 1.5 moles of PbO are lost; for each mole of NbO_2.5 added, 0.5 moles of PbO are gained. These results agree with the proposed model and with ionic size arguments. The weight changes were time-dependent during the first 30 to 40 h at 1150°C. This behavior is accounted for by the presence of transient second phases.     

Electrical Condultion and Polarization in Lead Silicate Glasses

Thermally stimulated polarization and depolarization current (TSPC/TSDC) and dc conductivity measurements on a series of lead silicate glasses were made between −196° and 190°C. The general composition of the glasses was xPbO·(100 − x )SiO₂, where x = 30, 40, 45, 50, and 65. The dc conductivity exhibits a monotonic increase with increasing PbO content. For x > 45, the rise in conductivity with increasing PbO content is much less than for x < 45. Two TSDC peaks have been observed in all the glasses. The smaller of the two TSDC peaks, occurring at lower temperatures, increases linearly in size with increasing concentrations of PbO. The high-temperature TSDC peak does not saturate from −196° to 190°C. Direct current conductivity in these glasses is ionic and due to the motion of Pb²⁺ ions. The behavior of the low-temperature TSDC peak is consistent with the hypothesis that it is caused by short-range motion (orientational polarization) of Pb²⁺ ions. The origin of the high-temperature TSDC peak is tentatively attributed to space charge polarization of Pb²⁺ ions.     

Sintering Behavior of Cadmium-Doped Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 Ceramics

Substituting Cd²⁺ ions into the A and B sites in a Pb(Ni_1/3Nb_2/3)O₃PbZrO₃PbTiO₃ (PNNPZPT) ternary perovskite material made it possible to determine the effects of the Cd²⁺ ion substitution site on sintering behavior. The substitution site of the Cd²⁺ ion was identified by using X-ray photoelectron spectroscopy spectra. Although Cd²⁺ ions were substituted into the A and B sites in PNNPZPT, the Cd²⁺ ions preferred the A site over the B site. When Cd²⁺ ions replaced Pb²⁺ ions, a weight gain was observed during sintering. On the other hand, replacing Ni2 ions with Cd²⁺ ions promoted weight loss. Those weight changes indicated that Cd²⁺ ions change the bonding strength between the B-site cations and the oxygen of the octahedron in a perovskite structure. Density was influenced by the Cd²⁺ ion substitution site, and the A-site-doped compositions had higher densities than the B-site-doped compositions.     

Li2O─SiO2─Al2O3─MeIIO Glass-Ceramic Systems for Tile Glaze Applications

In order to verify the possibility of using glass-ceramic materials as tile coatings, the devitrification processes of three industrial formulations belonging to the Li₂O─Al₂O₃─SiO₂ glass-ceramic system were investigated by differential thermal analysis, X-ray diffractometry, scanning electron microscopy, and IR spectroscopy. Compositional variations were made by addition of large amounts of MgO or CaO or PbO (ZnO) oxides as well as through smaller additions of other oxides. In these systems the surface crystallization contributes appreciably to the bulk crystallization mechanism. All the systems investigated show a high tendency toward crystallization even at very high heating rates, developing a very close network of interlocked crystals of synthetic β-spodumene-silica solid solutions (LiAlSi₄O₁₀). The results of this research are expected to establish the conditions under which these glass-ceramic systems can be practically used as tile glazes.     

Effects of M3+ Ions on the Conductivity of Glasses and Glass-Ceramics in the System Li2O—M2O3—GeO2—P2O5 (M = Al, Ga, Y, Dy, Gd, and La)

Glasses with compositions Li_1.2M_0.2Ge_1.8(PO₄)₃ (M = Al, Ga, Y, Gd, Dy, and La) were prepared and converted to glass-ceramics by heat treatment. The effects of the M³⁺ ions on the conductivity of the glasses and glass-ceramics were studied. The main phase present in the glass-ceramics was the conductive phase LiGe₂(PO₄)₃. Al³⁺ and Ga³⁺ ions entered the LiGe₂(PO₄)₃ structure by replacing Ge⁴⁺ ions, but lanthanide ions did not. The glass-ceramics exhibited much higher conductivity than the glasses. With increased ionic radius of the M³⁺ ions, the conductivity remained almost unchanged at ∼3 × 10⁻¹² S/cm for the glasses, but it decreased from 1.5 × 10⁻⁵ to 8 × 10⁻⁹ S/cm for the glass-ceramics at room temperature. The higher conductivity for Al³⁺- and Ga³⁺-containing glass-ceramics was suggested to result from the substitutions of Al³⁺ and Ga³⁺ ions for Ge⁴⁺ ions in the LiGe₂(PO₄)₃ structure.     

Subsolidus Phase Relationships in Part of the System Si,Al,Y/N,O: The System Si3N4─AIN─YN─Al2O3─Y2O3

The subsolidus phase relationships in the system Si,Al,Y/N,O were determined. Thirty-nine compatibility tetrahedra were established in the region Si₃N₄─AIN─Al₂O₃─Y₂O₃. The subsolidus phase relationships in the region Si₃N₄─AIN─YN─Y₂O₃ have also been studied. Only one compound, 2YN:Si₃N₄, was confirmed in the binary system Si₃N₄─YN. The solubility limits of the α'─SiAION on the Si₃N₄─YN:3AIN join were determined to range from m = 1.3 to m = 2.4 in the formula Y _{m /3}Si_{12- m} Al _m N₁₆. No quinary compound was found. Seven compatibility tetrahedra were established in the region Si₃N₄─AIN─YN─Y₂O₃.     

Photoluminescence Characteristics of Energy Transfer Between Eu3+and Bi3+in LiEu1−xBix (WO4)0.5(MoO4)1.5

A series of novel red phosphors LiEu_{1− x} Bi _x (WO₄)_0.5(MoO₄)_1.5 ( x =0, 0.05, 0.10, 0.15, 0.20, 0.30, 0.40, and 0.50) were synthesized by the conventional solid-state reaction method. The spectrum and the crystal structure of the phosphors were characterized by Fluorescence spectrophotometry and X-ray diffraction, respectively. The photoluminescent results show that all samples can be excited efficiently by UV (396 nm) and blue (467 nm) light and that they emit red light at 615 nm with line spectra, which are coupled well with the characteristic emissions from UVLED and blue light-emitting diode (LED), respectively. There is an efficient energy transfer from Bi³⁺ to Eu³⁺ ions, leading to the emission intensity of Eu³⁺ being enhanced by 1.5 times, and even more when Bi³⁺ ions are introduced into LiEu (WO₄)_0.5(MoO₄)_1.5. The introduction of Bi³⁺ ions broadened the excitation band of the phosphor, and the optimum doping concentration is found to be 10 mol% of Bi³⁺.     

2223 Phase Formation in Bi(Pb)─Sr─C─a─Cu─O: II, The Role of Temperature—Reaction Mechanism

The formation mechanism, the temperature range for the growth, and the thermal stability of the 2223 phase in Bi(Pb)─Sr─Ca─Cu─O have been investigated using DTA/TG, XRD, SEM/EDAX, TEM, EPMA, four-probe resistance and acsusceptibility measurement. The formation of the 2223 phase was found to follow a dissolution–precipitation process. A 2212 phase first reacts with the liquid phase formed via an incongruent melting of the Ca₂PbO₄ phase, and a dissolution of CaO and CuO takes place. The 2201 phase, which has the largest negative free energy, is then precipitated from the melt; the nucleation and growth of the 2223 phase are subsequently developed by the reaction between the 2201 phase precipitates and ions of Ca²⁺ and Cu²⁺ present in the liquid phase. The 2223 phase is formed at temperatures in the range 827°C T < 856°C. The optimum temperature T _f for the formation of 2223 phase is 845°± 5°C. The 2223 phase is thermodynamically unstable at temperatures above 856°C.     

Subsolidus Relations in the La2O3─CuO─CaO Phase Diagram and the La2O3─CuO Binary Join

The phase diagram for the CuO-rich part of the La₂O₃─CuO join was redetermined. La₂Cu₂O₅ was found to have a lower limit of stability at 1002°± 5°C and an incongruent melting temperature of ∼1035°C. LagCu₇O₁₉ had both a lower (1012°± 5°C) and an upper (1027°± 5°C) limit of stability. Subsolidus phase relations were studied in the La₂O₃─CuO─CaO system at 1000°, 1020°, and 1050°C in air. Two ternary phases, La_1.9Ca_1.1Cu₂O_5.9 and LaCa₂Cu₃O_8.6, were stable at these temperatures, with three binary phases, Ca₂CuO₃, CaCu₂O₃, and La₂CuO₄. La₂Cu₂O₅ and La₈Cu₇O₁₉ were stable only at 1020°C, and did not support solid-solution formation.     

Thermodynamic Assessment of the ZrO2─YO1.5 System

An optimal set of thermodynamic functions for the ZrO₂─YO_1.5 system are obtained using phase diagram and thermodynamic data. The liquid is described by a subregular solution model. Both cubic ZrO₂ and YO_1.5 solid solutions are regarded as one cubic solution, which is also treated as a subregular solution. The ordered Zr₃Y₄O₁₂ phase is treated as a stoichiometric compound. A regular solution model is applied to the other solid solutions. Tentative equilibrium boundaries between monoclinic and tetragonal ZrO₂ solid solutions are evaluated from information about the T ₀ line. The calculated phase diagram and thermodynamic functions agree well with experimental data.     

Low-Temperature Synthesis of Lead Tantalate Pyrochlore Solid Solutions Pb1.5+x(Ta2−yPby)O7−δ (0.0 < x < 0.5; 0.0 < y < 0.6)

Synthesis of lead tantalate pyrochlores by the reaction of PbO and Ta₂O₅ in various molar ratios between 1.5 and 4.0 at low temperatures (500–650°C) has been carried out. It has been shown that when PbO is reacted with Ta₂O₅ in various molar ratios at low temperatures, metastable lead tantalate pyrochlore solid solutions having cubic symmetry are formed. X-ray diffraction data give evidence for an increase in the a lattice parameter with increasing PbO content and partial occupancy of Pb in the Ta sites leading to the formula Pb_{1.5+ x} ²⁺(Ta_{2− y} Pb _y ⁴⁺)O_7−δ (0.0 < x < 0.5; 0.0 < y < 0.6) for this phase. It has also been found that the intermediate members of the solid solutions are metastable and tend to segregate into Pb-deficient and Pb-excess compositions leading to significant compositional inhomogeneity for the intermediate members.     

Peculiar Dielectric Behaviors of (Na1/2Bi1/2)0.87Pb0.13TiO3 Thin Films

PbTiO₃-doped sodium bismuth titanate (Na_1/2Bi_1/2)_{1− x} Pb _x TiO₃ of perovskite structure is one of the best-known piezoelectrics/ferroelectrics. However, it has not been properly investigated in any thin-film forms. In this study, the dielectric properties of (Na_1/2Bi_1/2)_0.87Pb_0.13TiO₃ thin films synthesized via a sol–gel route were investigated. They exhibit a strong frequency dispersion of the dielectric permittivity at relatively high frequencies, which is shifted to lower frequencies with increasing temperature. The electrical behavior can be fitted using Jonscher's universal law for dielectric relaxation. The peculiar dielectric behaviors observed can be ascribed to the coexistence of two different dielectric phases in the films, which is believed to be associated with the growth of the local Pb²⁺TiO₃ nanoclusters upon substitution of Pb²⁺ for Na⁺/Bi³⁺ in the (Na_1/2Bi_1/2)_{1− x} Pb _x TiO₃ films.     

Copper ⇌ Alkali Ion Exchange of Alkali Aluminosilicate Glasses in Copper-Containing Molten Salt: II, Divalent Copper Salts, CuCl2 and CuSO4

The ion-exchange mechanism between copper and alkali ions, when 20R₂O · 10Al₂O₃· 70SiO₂ (R = Li, Na, and K) glasses are immersed in divalent copper-containing molten salts in air and nitrogen at 550°C, has been investigated. In molten CuCl₂, the ion-exchange behavior in both air and nitrogen was very close to that in molten CuCl in air reported previously. This is explained by assuming that CuCl₂ decomposes into CuCl and Cl₂ at 550°C and the Cu⁺ ions thus formed mainly diffuse in glasses to replace alkali ions, where Cl₂ acts as an oxidizing agent just like oxygen. In the case of molten CuSO₄─₂SO₄, a small amount of Cu⁺ which is present in the molten state plays a primary role in the Cu ⇌ R⁺ ion exchange process, although the contribution of direct Cu²⁺⇌ 2R⁺ ion exchange cannot be ignored.