Conductivity of a new pyrophosphate Sn0.9Sc0.1(P2O7)1−δ prepared by an aqueous solution method

New pyrophosphate Sn_0.9Sc_0.1(P₂O₇)_1−δ was prepared by an aqueous solution method. The structure and conductivity of Sn_0.9Sc_0.1(P₂O₇)_1−δ have been investigated. XRD analysis indicates that Sn_0.9Sc_0.1(P₂O₇)_1−δ exhibits a 3 × 3 × 3 super structure. It was found that Sn_0.9Sc_0.1(P₂O₇)_1−δ prepared by an aqueous method is not conductive. The total conductivity of Sn_0.9Sc_0.1(P₂O₇)_1−δ in open air is 2.35 × 10⁻⁶ and 2.82 × 10⁻⁹ S/cm at 900 and 400 °C respectively. In wet air, the total conductivity is about two orders of magnitude higher (8.1 × 10⁻⁷ S/cm at 400 °C) than in open air indicating some proton conduction. SnP₂O₇ and Sn_0.92In_0.08(P₂O₇)_1−δ prepared by an acidic method were reported fairly conductive but prepared by similar solution methods are not conductive. Therefore, the conductivity of SnP₂O₇-based materials might be related to the synthetic history. The possible conduction mechanism of SnP₂O₇-based materials has been discussed in detail.     

Magnetic properties of (Fe)1−x–(Al2O3)x and (Fe50Ni50)1−x–(Al2O3)x nanocomposite magnetic media synthesized using gel like Al2O3 matrix

Composites with ferromagnetic nanoparticles, Fe and Fe₅₀Ni₅₀, dispersed in Al₂O₃ have been synthesized by a solution phase technique. The structure and magnetic properties of these composites with varying fractions of Al₂O₃ have been investigated. Both Fe and Fe₅₀Ni₅₀ nanoparticles are amorphous in the as-prepared state and become crystalline on heat treating with near equilibrium lattice parameters of 0.287 nm and 0.358 nm respectively. The interparticle distance increases with increasing Al₂O₃ from 0 wt.% to 20 wt.%. The size of Fe nanoparticles is 40 nm while the Fe₅₀Ni₅₀ nanoparticles are 20 nm in size. The Fe and Fe₅₀Ni₅₀ nanoparticles dispersed composites are found to be ferromagnetic at room temperature both in the as-prepared and heat treated conditions with clear coercive fields of 5.5–35 × 10³ A m⁻¹. The saturation magnetization increases by orders of magnitude on heat treatment, for e.g. from <1.0 emu g⁻¹ to 143.4 emu g⁻¹ for Fe–15 wt.% Al₂O₃ and 95.6 emu g⁻¹ for Fe₅₀Ni₅₀–15 wt.% Al₂O₃. The Fe-composites exhibit a Curie transition at 1000 K while the Fe₅₀Ni₅₀ composites exhibit a transition at 880 K, both temperatures close to bulk values.     

New dielectric material system of La(Mg1/2Ti1/2)O3–Ca0.6La0.8/3TiO3 for microwave applications

The microstructure and microwave dielectric properties of xLa(Mg_1/2Ti_1/2)O₃–(1 − x)Ca_0.6La_0.8/3TiO₃ ceramics system with ZnO additions (0.5 wt.%) investigated by the conventional solid-state route have been studied. Doping with ZnO (0.5 wt.%) can effectively promote the densification and the dielectric properties of xLa(Mg_1/2Ti_1/2)O₃–(1 − x)Ca_0.6La_0.8/3TiO₃ ceramics. 0.6La(Mg_1/2Ti_1/2)O₃–0.4Ca_0.6La_0.8/3TiO₃ ceramics with 0.5 wt.% ZnO addition possess a dielectric constant (_r) of 43.6, a Q × f value of 48,000 (at 8 GHz) and a temperature coefficient of resonant frequency (τ_f) of −1 ppm/°C sintering at 1475 °C. As the content of La(Mg_1/2Ti_1/2)O₃ increases, the highest Q × f value of 62,900 (GHz) for x = 0.8 is achieved at the sintering temperature 1475 °C. A parallel-coupled line band-pass filter is designed and simulated using the proposed dielectric to study its performance.     

Thermodynamic studies on LaFeO3(s)

The enthalpy increments and the standard molar Gibbs energies in the formation of LaFeO₃(s) have been measured using a high-temperature Calvet micro-calorimeter and a solid oxide galvanic cell, respectively. The corresponding expression for enthalpy increments is given as:

H°(T)−H°(298.15 K)(J mol⁻¹)(±1.2%)=−36887.27+103.53 T(K)+25.997×10⁻³T²(K)+11.055×10⁵/T(K).

The heat capacity, the first differential of H°(T)−H°(298.15 K) with respect to temperature, is given as:

C_p,m°(T)(JK⁻¹mol⁻¹)=103.53+51.994×10⁻³T(K)−11.055×10⁵/T²(K).

From the measured e.m.f. of the cell, (−)Pt/(LaFeO₃(s)+La₂O₃(s)+Fe(s))//CSZ//(Ni(s)+NiO(s))/Pt(+), and the relevant Δ_fG_m°(T) values from the literature, the Δ_fG_m°(LaFeO₃, s, T) was calculated, and is given as:

Δ_fG_m°(LaFeO₃, s, T)(kJmol⁻¹)(±0.72)=−1319.2+0.2317T(K).

The calculated Δ_fH_m°(LaFeO₃, s, 298.15 K) and S°(298.15 K) values obtained using the second law method are −1334.7 kJ mol⁻¹ and 128.9 J K⁻¹ mol⁻¹, respectively.     

Study of (1 − x)(Mg0.6Zn0.4)0.95Co0.05TiO3–xCa0.61Nd0.26TiO3 microwave dielectrics

The microwave dielectric properties and the microstructures of the (1 − x)(Mg_0.6Zn_0.4)_0.95Co_0.05TiO₃–xCa_0.61Nd_0.26TiO₃ ceramic system were investigated. In order to achieve a temperature-stable material, we studied a method of combining a positive temperature coefficient material with a negative one. Ca_0.61Nd_0.26TiO₃ has a large positive temperature coefficient of resonant frequency. (Mg_0.6Zn_0.4)_0.95Co_0.05TiO₃ possesses a negative temperature coefficient of resonant frequency. By appropriately adjusting the x value in the (1 − x)(Mg_0.6Zn_0.4)_0.95Co_0.05TiO₃–xCa_0.61Nd_0.26TiO₃ ceramic system, a near-zero τ_f value can be obtained. A new microwave dielectric material of 0.8(Mg_0.6Zn_0.4)_0.95Co_0.05TiO₃–0.2Ca_0.61Nd_0.26TiO₃ possesses the excellent dielectric properties of a dielectric constant of 28.6, a Q × f value of 80,600 GHz and a temperature coefficient of resonant frequency of 4.1 ppm/°C and has a lower sintering temperature of 1250 °C.     

Electrochemical performances of Ag–(Bi2O3)0.75(Y2O3)0.25 composite cathodes

The electrochemical performances of Ag–Y_0.25Bi_0.75O_1.5 (YSB) composite cathodes on Ce_0.8Sm_0.2O_1.9 (SDC) electrolytes have been investigated at intermediate temperature using AC impedance spectroscopy. The results indicated that the electrochemical performances of these composites are quite sensitive to the compositions and the microstructures of the cathode. The optimum YSB addition to Ag resulted in 10 times lower area specific resistance. The ASR of Ag-50 vol.% YSB was about 0.12 Ωcm² at 700 °C as compared to 3.9 Ωcm² for Ag cathodes. The observed high performance of Ag–YSB composite cathodes might be due to the high oxygen-ion conductivity of YSB and its high catalytic activity for oxygen reduction.     

Structural, magnetic and electrical properties of (La0.70−xNdx)Sr0.30Mn0.70Cr0.30O3 with 0 ≤ x ≤ 0.30

The structural, magnetic and electrical properties of (La_0.70−xNd_x)Sr_0.30Mn_0.70Cr_0.30O₃ perovskites (0 ≤ x ≤ 0.30) prepared by the usual ceramic procedure were investigated. Structural Rietveld refinement revealed that these compounds crystallize in a rhombohedral perovskite structure when x = 0, 0.10 and 0.20, while for x = 0.30 the structure becomes orthorhombic (Pbnm). It was found that the substitution of La by Nd reduces the Curie temperature (T_C). The FC, ZFC, M(H) and AC susceptibility measurements show typical canted-antiferromagnetism for the Nd-doped samples, in which a ferromagnetic component coexists with predominant antiferromagnetic interactions. The values of the magnetization (M(H)) decrease very slightly when increasing the Nd content, compared to the undoped sample (M_S values at 5 T and 2 K are, respectively, 47.9, 47.3 and 47.5 emu/g for x = 0.10, 0.20 and 0.30, compared to 48.2 emu/g for x = 0), indicating that the Nd³⁺ contribution is negligible compared to the total moment of the ferromagnetic (Mn/Cr) network. The resistivity increases by several orders of magnitude with Nd-doping and the semi-conducting behaviour persists in the whole temperature range. The interaction between Mn⁴⁺–O–Cr³⁺and Cr³⁺–O–Cr³⁺ is responsible for the semi-conducting state.     

Microstructure and electrical properties of Y(NO3)3·6H2O-doped ZnO-Bi2O3-based varistor ceramics

Y(NO₃)₃·6H₂O-doped ZnO-Bi₂O₃-based varistor ceramics were prepared using a solid reaction route. The microstructure, electrical properties, degradation coefficient (D_V), and dielectric characteristics of varistor ceramics were studied in this paper. With increasing amounts of Y(NO₃)₃·6H₂O in the starting composition, Y-containing Bi-rich, Y₂O₃, and Sb₂O₄ phases were formed, and the average grain size decreased. Results also showed that with the addition of 0.16 mol% Y(NO₃)₃·6H₂O, Y(NO₃)₃·6H₂O -doped ZnO-based varistor ceramics exhibit comparatively better comprehensive electrical properties, such as a threshold voltage of 425 V/mm, a nonlinear coefficient of 73.9, a leakage current of 1.78 μA, and a degradation coefficient of 1.7. The dielectric characteristics and lightning surge test also received the same additional content of Y(NO₃)₃·6H₂O. The results confirmed that doping with rare earth nitrates instead of rare earth oxides is very promising route in preparing high-performance ZnO-Bi₂O₃-based varistor ceramics.     

Preparation and characteristic of spherical Li3V2(PO4)3

Spherical Li₃V₂(PO₄)₃ was synthesized by using N₂H₄ as reducer. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that single-phase, spherical and well-dispersed Li₃V₂(PO₄)₃ has been successfully synthesized in our experimental process. Electrochemical behaviors have been characterized by charge/discharge measurements. The initial discharge capacities of Li₃V₂(PO₄)₃ were 123 mAh g⁻¹ in the voltage range of 3.0–4.3 V and 132 mAh g⁻¹ in the voltage range of 3.0–4.8 V.     

Self-healing mechanism of a protective film prepared on a Ce(NO3)3-pretreated zinc electrode by modification with Zn(NO3)2 and Na3PO4

Self-healing mechanism of a protective film against corrosion of zinc at scratches in an aerated 0.5 M NaCl solution was investigated by polarization measurements, X-ray photoelectron spectroscopy (XPS) and electron-probe microanalysis (EPMA). The film was prepared on a zinc electrode by treatment in a Ce(NO₃)₃ solution and addition of aqueous solutions containing 9.98 or 19.9 μg/cm² of Zn(NO₃)₂ · 6H₂O and 55.2 μg/cm² of Na₃PO₄ · 12H₂O. After the coated electrode was scratched with a knife-edge crosswise and immersed in the NaCl solution for many hours, polarization measurements, observation of pit formation at the scratches, XPS and EPMA were carried out. This film was remarkably protective and self-healing against zinc corrosion on the scratched electrode. The cathodic and anodic processes of zinc corrosion were markedly suppressed by coverage of the surface except for scratches with a thin Ce₂O₃ layer containing a small amount of Ce⁴⁺ and the surface of scratches with a layer composed of Zn₃(PO₄)₂ · 4H₂O, Zn(OH)₂ and ZnO mostly.     

Phase relations and flux research for zinc oxide crystal growth in the ZnO–K2O–P2O5 system

The subsolidus phase relations of the ternary system ZnO–K₂O–P₂O₅ were investigated by means of X-ray diffraction (XRD). There are 7 binary compounds, 6 ternary compounds and 20 three-phase regions in this system. The phase diagram of the pseudo-binary system KZn₄(PO₄)₃–ZnO was also investigated by means of XRD and differential thermal analysis (DTA) methods. KZn₄(PO₄)₃–ZnO is a eutectic system with eutectic temperature about 952 °C and eutectic point at about 2 mol% ZnO. Only narrow composition range in the KZn₄(PO₄)₃–ZnO system is suitable for the growth of ZnO crystals.     

X-ray scattering from Co0.83[Pt(C2O4]2]·6H2O: A system with two coupled order parameters

X-ray studies of the quasi-one-dimensional conductor Co_0.83 [Pt(C₂O₄)₂]·6H₂O, Co(def)OP, show both a Peierls distortion with a period of 2k_F = 1.70·2π/c and a separate (earlier reported) three-dimensional superlattice. The two distortions couple, so that the drastic decrease in electrical conductivity is accompanied by the occurence of the superlattice spots with a common critical temperature, T = (297 ± 4)K. The striking differences between Co(def)OP and Mg(def)OP are discussed and explained in terms of the different atomic structures of the cations.     

Subsolidus phase relations of the ZnO–Li2O–P2O5 system

As a systematic search for suitable flux to grow zinc oxide single crystals, the subsolidus phase relations of the ternary system ZnO–Li₂O–P₂O₅ were investigated by means of X-ray diffraction (XRD). There are 6 binary compounds, 5 ternary compounds and 17 three-phase regions in this system. A new compound, Li₆Zn(P₂O₇)₂, is found in this system based on XRD experiments. The phase diagrams of the pseudo-binary systems Li₃PO₄–ZnO and LiZnPO₄–ZnO are investigated. It shows that the compounds, Li₃PO₄ and LiZnPO₄, are not suitable as flux for the growth of ZnO single crystals below 1250 °C.     

Synthesis of CeO2/TiO2 nanoparticles by laser ablation of Ti target in cerium (III) nitrate hexahydrate (Ce(NO3)3·6H2O) aqueous solution

A new synthesis process, laser ablation in an aqueous solution of target material, was applied to synthesize nanostructured CeO₂/TiO₂ catalyst particles. Reactivity within the laser plume (plasma) can be used to synthesize CeO₂ from an aqueous solution, 2 M cerium (III) nitrate hexahydrate (Ce(NO₃)₃·6H₂O) aqueous solution, and to fabricate TiO₂ from Ti target. CeO₂/TiO₂ nanoparticles were successfully synthesized by the laser ablation of Ti target in 2 M cerium (III) nitrate hexahydrate (Ce(NO₃)₃·6H₂O) aqueous solution. Laser ablation of Ti in a liquid environment and chemical reactions of the solution within a plasma plume are discussed.     

Improved high-Q microwave dielectric resonator using ZnO-doped La(Co1/2Ti1/2)O3 ceramics

The microwave dielectric properties and the microstructures of ZnO-doped La(Co_1/2Ti_1/2)O₃ ceramics prepared by conventional solid-state route have been studied. Doped with ZnO (up to 0.75 wt%) can effectively promote the densification of La(Co_1/2Ti_1/2)O₃ ceramics with low sintering temperature. At 1320 °C, La(Co_1/2Ti_1/2)O₃ ceramics with 0.75 wt% ZnO addition possesses a dielectric constant (_r) of 30.2, a Q × f value of 73,000 GHz (at 8 GHz) and a temperature coefficient of resonant frequency (τ_f) of −35 ppm/°C.     

Parallelogram-like microparticles of calcium dihydrogen phosphate monohydrate (Ca(H2PO4)2·H2O) obtained by a rapid precipitation route in aqueous and acetone media

Calcium dihydrogenphosphate monohydrate (Ca(H₂PO₄)₂·H₂O) was prepared by a rapid and simple precipitation method using CaCO₃ and H₃PO₄ in aqueous and acetone media at ambient temperature. The thermal transformation of the synthesized Ca(H₂PO₄)₂·H₂O at 500 °C was obtained to be CaP₂O₆ occurred through the dehydration and the phosphate condensation reactions, as revealed by thermoanalytical techniques (TG/DTG/DTA). The synthesized Ca(H₂PO₄)₂·H₂O and its decomposition product CaP₂O₆ were characterized by X-ray powder diffraction (XRD), Fourier transfer infrared (FTIR) spectroscopy and scanning electron microscope (SEM). Thermal behavior and the morphology of the synthesized Ca(H₂PO₄)₂·H₂O in aqueous and acetone media are compared with those of other works. The SEM micrograph of Ca(H₂PO₄)₂·H₂O show parallelogram-like microparticles containing small and large grain sizes. The aqueous and acetone media are proposed to play an important role in the synthetic process of calcium phosphates in exhibiting different physical properties, which are important for specific applications.     

Crystallization kinetics of new compound of V2O5–PbO–Li2O–Fe2O3 glass using differential thermal analysis

Different glasses with nominal compositions of (70 − x)V₂O₅–xPbO–20Li₂O–10Fe₂O₃ (0 ≤ x ≤ 12.5 mol.%) were successfully obtained by the melt quenching technique. Crystallization kinetics of these glasses was studied under non-isothermal conditions using the formal theory of transformations for heterogeneous nucleation. The procedure was applied to the experimental data obtained by differential thermal analysis, using several measurements at different heating rates. In addition, from the heating rate dependence of the glass transition temperature, the glass transition activation energy was derived. The crystallization results are analyzed and both the activation energy of crystallization process and the crystallization mechanism are characterized in terms of Gao–Wang method. The phases at which the glass crystallizes after the thermal process have been identified by X-ray diffraction. The diffractogram of the transformed material indicates the presence of microcrystallites of LiV₁₅O_35.5, Pb₃(VO₄)₂ and PbO₂ beside the remaining an additional amorphous matrix.     

Substitutionsvarianten von Nickel(II) amid: ternäre amidoniccolate mit Lithium und Caesium Li3Ni4(NH2)11·NH3 und Cs2Ni(NH2)4·NH3

The red substance Li₃Ni₄(NH₂)₁₁·NH₃ crystallizes from liquid ammonia at room temperature when LiNO₃, LiCl or LiBr reacts with Na₂Ni(NH₂)₄ in a pressure-resistant glass vessel. A similar reaction between CsNH₂ and Ni(NH₂)₂ gives orange crystals of Cs₂Ni(NH₂)₄ ·NH₃. X-ray investigations gave the following data: Li₃Ni₄(NH₂)₁₁·NH₃: Pna2₁; fZ = 4; ; ; ; p(X-ray) = 1.942 g cm⁻³; N(F_o² 3σ(F_o²) = 944; N(Variable) = 157; R/R_w = 0.059/0.072. Cs₂Ni(NH₂)₄ · NH₃: P2₁/c; Z = 4; ; ; ; β = 129.96(3)°; p(X-ray = 2.960 g cm⁻³;N(F_o² 3σ(F_o²) = 1488; N(Variable) = 73; R/R_w = 0.045/0.052. The synthesis, thermal behaviour, IR spectroscopic characteristics and crystal structures of the compounds are reported and comparisons made with Ni(NH₂)₂ and other amidonickel(II) compounds.     

Crystal structure of Nax(MoO)5(P2O7)4 studied by synchrotron X-ray diffraction

The crystal structure of sodium pentamolybdyl tetradiphosphate Na_x(MoO)₅(P₂O₇)₄ has been determined from synchrotron diffraction data collected at 293 K on two microcrystals. The compound crystallizes in a monoclinic space group I 1 1 2/a (no. 15, setting 11), with unit cell parameters a = 22.905(3), b = 23.069(2), c = 4.8537(2) Å, γ = 90.641(9)° and a = 22.898(3), b = 23.056(2), c = 4.8551(2) Å, γ = 90.82(1)°, for crystals I and II, respectively. The structure is pseudo-tetragonal, and the crystals are pseudo-merohedrally twinned by 90° rotation around the c-axis. The structure closely resembles the previously reported Li-deintercalated Mo_1.3OP₂O₇ [V.V. Lisnyak, N.V. Stus, P. Popovich, D.A. Stratiychuk, Ya. Filinchuk, V.M. Davydov, J. Alloys Compd. 360 (2003) 81–84]. Comparison of the two structures led us to conclude that the Mo₂ and Mo₃ clusters were erroneously identified in Mo_1.3OP₂O₇. A revised structure of Mo_1.3OP₂O₇ contains a fully occupied oxygen site instead of the 16% occupied Mo(2) site, thus the revised formulae for the Li-deintercalated compound is (MoO)₅(P₂O₇)₄. In both structures, the (MoO)₅(P₂O₇)₄ framework strongly resembles the one in the earlier reported Ag(MoO)₅(P₂O₇)₄, while the location of Na and Ag atoms differ.     

Structural and piezoelectric properties of LiNbO3-modified BiScO3–PbTiO3 ceramics

Piezoelectric perovskite materials based on the solid solution (1 − x)BiScO₃–xPbTiO₃ (BSPT) have been attracting attention for their high Curie temperature (T_c = 450 °C) and excellent piezoelectric properties. The LiNbO₃ (LN), which has a T_c as high as 1150 °C, has been recently reported forming a phase pure perovskite solid solution with some perovskite structure compounds. In the current work, the effects of LN substitution on the structural and electrical properties of BSPT ceramics were investigated in the 0.36BiScO₃–0.64{(1 − x)PbTiO₃–xLiNbO₃} (BSPTLNx) system. The results of LN addition in the BSPT ceramics show significant enhancement of the piezoelectric properties. The piezoelectric constant d₃₃, planar electromechanical coupling coefficient and remnant polarization P_r values reached 465 pC/N, 0.57 and 48 μC/cm², respectively, for x = 0.04. The T_c gradually decreases with increasing LN content in the BSPTLNx system, due to the structure transform from the tetragonal to the rhombohedral. A typical relaxor behavior is also produced with the LN substitution in the BSPTLNx system.