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Abstract: The solid solutions in the system of Ca and Pb hydroxyapatite, Ca10− χ Pb χ HA (χ =0–10), were successfully synthesized by high-temperature mixing method (HTMM) at 200°C for 12h under hydrothermal conditions. The samples were characterized by X-ray diffraction, chemical analysis and electron microscopic observation, and the site of the metal ions in the solid solutions was analyzed with the Rietveld method. The lattice parameters of the solid solutions prepared by both of the methods didn’t vary linearly with Pb contents, and they have two turning points of 0.4 and 0.6 of Pb content. It was found that Pb ions in the solid solutions preferentially occupied the M (2) site in the apatite structure. HTMM gives Ca–Pb HA solid solutions much better crystallization. However, due to the formation of intermediate compound of Pb3O2(OH)2 in the Pb(NO3)2·4H2O solution before mixing with (NH4)2HPO4 solution at 200°C, HTMM causes the decrease of crystallization of the samples with high Pb content. [Copyright &y& Elsevier]

Abstract: 0.55Pb(Ni1/3Nb2/3)O3–0.45Pb(Zr0.3Ti0.7)O3(PNN–PZT) ceramics with different concentration of xFe2O3 doping (where x =0.0, 0.8, 1.2, 1.6mol%) were synthesized by the conventional solid state sintering technique. X-ray diffraction analysis reveals that all specimens are a pure perovskite phase without pyrochlore phase. The density and grain size of Fe-doped ceramics tend to increase slightly with increasing concentration of Fe2O3. Comparing with the undoped ceramics, the piezoelectric, ferroelectric and dielectric properties of the Fe-doped PNN–PZT specimens are significantly improved. Properties of the piezoelectric constant as high as d 33 ~956 pC/N, the electromechanical coupling factor k p ~0.74, and the dielectric constant ε r ~6095 are achieved for the specimen with 1.2mol% Fe2O3 doping sintered at 1200°C for 2h. [Copyright &y& Elsevier]

Abstract: The present research describes a modified sol-gel technique used to obtain nano-crystalline potassium niobate (KNbO3) powders by using ethylene diamine tetraacetic acid (EDTA)/citrate as a complexing agent. The metal ions chemically interact with EDTA in the precursor sol. The aging treatments lead to the formation of a precursor-polymeric gel network. The effects of the amounts of citric acid and EDTA on the stability of the precursor sol are investigated. The influence of excess K on the formation of pure-phase KNbO3 powders is also studied. The obtained gels and powders are characterized by thermogravimetric-differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicate that a stable precursor sol is formed when n(CA):n(Mn+) = 3:1 and n(EDTA) :n(NH4OH) = 1:3.5. The xerogel is calcined at 700–850 °C to prepare the KNbO3 nano-powder. The smallest grain size of the sample obtained at 850 °C is about 60 nm when the K/Nb molar ratio equals 1.2. [Copyright &y& Elsevier]

Pure (K,Na)NbO (KNN) powders have been successfully prepared by using traditional hydrothermal method and high-temperature mixing method (HTMM) under solvothermal and hydrothermal conditions. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to show the change of phase, morphology, and size of the as-prepared particles with the alkalinity of the starting solution. Compared with the traditional hydrothermal method, smaller particles with higher phase purity are prepared using HTMM under hydrothermal conditions. It is found that the alkalinity has significant effects on the crystal size. The KNN grain size first increases and then decreases with increasing alkalinity. Typical samples solvothermally synthesized in a mixed solvent with isopropanol/deionized water ratio of 50/50 by volume were made of well-crystallized single-crystalline nanoparticles with size of about 500 nm. [ABSTRACT FROM AUTHOR]

BaTiO nanoparticles were prepared for the first time employing a solvothermal process from the synthetic precursors of KTiO nano-whiskers. The obtained samples were characterized by X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and high-resolution transmission electron microscopy, etc. The results indicate that well-crystallized single-phase BaTiO nanoparticles are synthesized using KTiO as precursors under solvothermal conditions at as low as 0.9 M. The solvothermal method facilitates the crystallinity and formation of the BaTiO nanoparticles. However, the K ions cannot be completely replaced by Ba by the hydrothermal method even at 10 M due to its unique and extremely stable 'tunnel' structure. The solvothermal method provides new avenues for the ion-exchange synthesis of a variety of other perovskite-type materials such as MTiO (M = Pb, Sr, Ca, etc.). [ABSTRACT FROM AUTHOR]

Flower-like MoS 2 spheres were successfully prepared via a facile hydrothermal method. The effects of excess sulfur on the formation of MoS 2 were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The XRD pattern showed that the preferential orientation of the flower-like hexagonal 2H–MoS 2 spheres was the (002) plane, and I 002 / I 100 ratio values indicated that the (002) plane grew more completely than the (100) plane with increasing S/Mo ratio. The FESEM images revealed that the sheet thickness of the MoS 2 spheres increased to ~30 nm with increasing S/Mo ratio, exposing more edges on the nanosheets of the MoS 2 spheres. Photocatalytic properties of the products were studied, and the results showed that the MoS 2 sample with a S/Mo ratio of 2.75 exhibited the highest degradation rate constant and methylene blue degradation rate under 90 min visible light irradiation. The results showed that the enhancement of photocatalytic activity originated from increasing exposed area of the {100} facets with increasing S/Mo ratio under the hydrothermal environment. [ABSTRACT FROM AUTHOR]

A simple low-temperature solid-state reaction in the presence of the surfactant PEG400 was developed to obtain ZnO/CdS nanocomposites. The effects of synthesis temperature and reaction time on crystal structure and optical properties of the nanocomposites were investigated by several technologies. X-ray diffraction (XRD) and high resolution transmission electron microscope (HRTEM) characterizations showed that the products consisted of the nanoparticles, and the grain growth kinetics of the cubic CdS and the hexagonal ZnO phase in the nanocomposites was described. The mechanism analysis suggested that sufficient grinding and heating treatment was a key to form the ZnO/CdS nanocomposites, and the surfactant PEG400 was proved not to involve the reaction and prevent the nanoparticles from aggregating to larger in whole grinding and heat-treatment process. Ultraviolet–visible (UV–vis) spectra revealed that the band gaps of the nanocomposites could be tuned by the reaction temperature and reaction time. Photoluminescence (PL) spectra showed that the changing position and the intensity of the emission peaks resulted from the rate of electron transfer and recombination probability under the different conditions. [ABSTRACT FROM AUTHOR]

Abstract: (K, Na)(Nb, Sb)O3 (KNNS) lead-free peizoceramic powders were successfully synthesized by hydrothermal treatment at 240°C for 8h using the KOH, NaOH, Nb2O5 and Sb2O3 as raw materials. Effects of Sb-doping on the crystal structure and morphology of the as-prepared powders were investigated by powder X-ray diffraction (XRD), Raman spectra (Raman), scanning electron microscope (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The Sb element was successfully doped into the alkaline niobate perovskite structure to form crystalline (K0.7Na0.3)(Nb0.95Sb0.05)O3 lead-free piezoelectric ceramic powder, which has a hexagonal morphology due to the aggregation growth of small grains. Phase and morphology evolutions with the reaction time were also studied, and a possible formation mechanism was proposed. [Copyright &y& Elsevier]

Abstract: The solid solutions in the system of Pb and Sr hydroxyapatite, Sr10−x Pb x HAp (x =0–10), were successfully synthesized by high-temperature mixing method (HTMM) at 160°C for 12h under hydrothermal conditions. The samples were characterized by X-ray diffraction, chemical analysis and electron microscopic observation, and the site of the metal ions in the solid solutions was analyzed with the Rietveld method. The lattice constants, both a and c, of the solid solutions varied linearly with Pb content. It was found that Pb ions in the solid solutions preferentially occupied the M(2) site in the apatite structure. HTMM gives Sr–Pb HAp solid solutions much better crystallization. However, due to the formation of intermediate compound of Pb3O2(OH)2 in the Pb(NO3)2·4H2O solution before mixing with (NH4)2HPO4 solution at 160°C, HTMM causes the decrease of crystallization of the samples with high Pb content. [Copyright &y& Elsevier]

Abstract: In order to prepare the pure (K, Na)NbO3(KNN) particles with higher crystallinity, the high temperature mixing method (HTMM) under hydrothermal conditions was carried out in this work. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM). The results indicate that the KNN particles size decrease gradually with the increase of mineralization concentration in the starting solution. The ratio of K+/(K+ +Na+) in the starting solution has a great effect on the phase of the products, and several phases coexist in the product when the ratio of K+/(K+ +Na+) in the starting solution is 0.7. [Copyright &y& Elsevier]