Er3＋ doped potassium gadolinium molybdate （KGM） phosphor with sensitizer Yb3＋ ion was synthesized by the Pechini method using citric acid and ethylene glycol. The crystallization processes of the phosphor precurso...Er3＋ doped potassium gadolinium molybdate （KGM） phosphor with sensitizer Yb3＋ ion was synthesized by the Pechini method using citric acid and ethylene glycol. The crystallization processes of the phosphor precursors were characterized by X-ray diffraction （XRD） and thermogravimetry-differential scanning calorimetry （TG-DSC）, which indicated that ultrafine uniform crystallites of KGM：Er,Yb were obtained by sintering the precursors at above 650 ℃ for 5 h. Upconversion luminescence （UL） spectra of the samples were studied by a 976 nm semiconductor laser diode （LD） excitation. The UL spectra exhibited the green and red emission bands that were attributed to the 2H11/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3＋, respectively. The possible UL mechanisms of Er3＋ were explained by means of an energy level diagram. The maximum luminescent intensity was achieved when the concentration of Er3＋, Yb3＋ arrived at 1 mol.% and 20 mol.%, respectively.展开更多
Homogeneous (ZrO_2)_(0.92)(Sc_2O_3)_(0.08) solid solution in fluorite cubic structure was prepared from the gels with altered molar ratios of citric acid (CA) to metal ions (M) and ethylene glycol (EG) via a polymeriz...Homogeneous (ZrO_2)_(0.92)(Sc_2O_3)_(0.08) solid solution in fluorite cubic structure was prepared from the gels with altered molar ratios of citric acid (CA) to metal ions (M) and ethylene glycol (EG) via a polymerization route (Pechini method). Due to the enhanced chemical homogeneity (high level of mixing of metal ions and ligands) in the polymeric gels, Sc-doped zirconia can be crystallized at temperatures as low as 400 ℃. During the evolution from amorphous gel to the crystallized (ZrO_2)_(0.92)(Sc_2O_3)_(0.08) fine powder, the bonding nature between carboxylate groups and Zr/Sc cations changed: unidentate→bridging→ionic upon calcination. The molar ratios of CA/M (1～4) and CA/EG (0.2～4) were demonstrated to affect the thermal behavior of the gels and thus the particle properties of the derived nanoparticulate oxide powders (including particle size and surface area). The as-sintered sample compacted from the nanosized powders prepared by calcining the gel with the highest content of organics (CA/M=4 and CA/EG=0.2) exhibited the best sinterability and the highest oxide ion conductivity.展开更多
Pr0.6-x NdxCa0.4 FeO3-δ （ x = 0.0, 0.2, 0.3, 0.4, 0.5, 0.6） were synthesized using Pechini method. A number of studies were conducted concerning composition, specific area, crystalline structure and microstructure ...Pr0.6-x NdxCa0.4 FeO3-δ （ x = 0.0, 0.2, 0.3, 0.4, 0.5, 0.6） were synthesized using Pechini method. A number of studies were conducted concerning composition, specific area, crystalline structure and microstructure of the samples by means of FT-IR, BET, XRD TG-DTA and SEM. The results show that all the samples with different doping amounts of Pr^3＋ and Nd^3＋ on A-site are fine dispersed, and mean particle size less than 100 nm. The powders have good sinterability, and the relative density is 95% after sintered at 1200 ℃ for 2 h. It is found that all specimens are entirely single phase solid solutions with orthorhombic perovskite structure, the stable perovskitetype phase is formed completely after calcination at 900 ℃.展开更多
Lead-free piezoelectric thin films of 0.055BaZrO_(3)–0.935(K_(0.45)Na_(0.5)Li_(0.05))NbO_(3)–0.01(Bi_(0.5)Na_(0.5))TiO_(3)(BZ–KNLN–BNT)were fabricated on(100)-LaNiO_(3)/SiO_(2)/Si substrates.The Pechini(polymeric ...Lead-free piezoelectric thin films of 0.055BaZrO_(3)–0.935(K_(0.45)Na_(0.5)Li_(0.05))NbO_(3)–0.01(Bi_(0.5)Na_(0.5))TiO_(3)(BZ–KNLN–BNT)were fabricated on(100)-LaNiO_(3)/SiO_(2)/Si substrates.The Pechini(polymeric precursor)method was carried out to prepare the complicated multi-component precursor solution.This method was suited for controlling the complex components accurately.The films crystallized at 700℃ showed a(100)pc-oriented perovskite structure,whose grain size was about 200 nm and thickness was about 700 nm.The Curie temperature Tc of the films was 292℃ that was near to that of the bulk ceramics.The preparation method used in this work provided a possibility for the application of multi-component lead-free piezoelectric films.展开更多
The aim of the present work was to investigate the luminescent properties of europium-doped lanthanum aluminate (LaAlO3) powder prepared by Modified Pechini (MP) method. Samples were prepared at different Eu3+ concent...The aim of the present work was to investigate the luminescent properties of europium-doped lanthanum aluminate (LaAlO3) powder prepared by Modified Pechini (MP) method. Samples were prepared at different Eu3+ concentrations and calcined at 1600°C. Structural and morphology characterizations were obtained by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). Luminescent properties were analyzed by photoluminescence (PL) and thermoluminescent phenomena. The XRD pattern shows pure lanthanum aluminate oxide LaAlO3 with a rhombohedral structure. Photoluminescence studies of the powders was related to 4f → 4f(5D0 → 7Fi) (i = 1, 2, 3, 4) transitions of Eu3+ ion, the most intense emission of Eu3+ in LaAlO3 was registered for the transition 5D0 → 7F1, for 5% of Eu3+. The recorded TL glow curves of excited samples showed a main TL peak, the main peak appeared its maximum as a function of excitation energy. The investigation demonstrates that polycrystalline LaAlO3:Eu3+ powders calcined at 1600°C have interesting luminescent characteristics.展开更多
基金Project supported by Shandong Province Natural Science Foundation (Y2008F10)the Award Fund for Prominent Youth Scientists of Shandong Province (2008BS09006)Shandong Province Higher Educational Science and Technology Program (J10LD1810-13)
文摘Er3＋ doped potassium gadolinium molybdate （KGM） phosphor with sensitizer Yb3＋ ion was synthesized by the Pechini method using citric acid and ethylene glycol. The crystallization processes of the phosphor precursors were characterized by X-ray diffraction （XRD） and thermogravimetry-differential scanning calorimetry （TG-DSC）, which indicated that ultrafine uniform crystallites of KGM：Er,Yb were obtained by sintering the precursors at above 650 ℃ for 5 h. Upconversion luminescence （UL） spectra of the samples were studied by a 976 nm semiconductor laser diode （LD） excitation. The UL spectra exhibited the green and red emission bands that were attributed to the 2H11/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3＋, respectively. The possible UL mechanisms of Er3＋ were explained by means of an energy level diagram. The maximum luminescent intensity was achieved when the concentration of Er3＋, Yb3＋ arrived at 1 mol.% and 20 mol.%, respectively.
文摘Homogeneous (ZrO_2)_(0.92)(Sc_2O_3)_(0.08) solid solution in fluorite cubic structure was prepared from the gels with altered molar ratios of citric acid (CA) to metal ions (M) and ethylene glycol (EG) via a polymerization route (Pechini method). Due to the enhanced chemical homogeneity (high level of mixing of metal ions and ligands) in the polymeric gels, Sc-doped zirconia can be crystallized at temperatures as low as 400 ℃. During the evolution from amorphous gel to the crystallized (ZrO_2)_(0.92)(Sc_2O_3)_(0.08) fine powder, the bonding nature between carboxylate groups and Zr/Sc cations changed: unidentate→bridging→ionic upon calcination. The molar ratios of CA/M (1～4) and CA/EG (0.2～4) were demonstrated to affect the thermal behavior of the gels and thus the particle properties of the derived nanoparticulate oxide powders (including particle size and surface area). The as-sintered sample compacted from the nanosized powders prepared by calcining the gel with the highest content of organics (CA/M=4 and CA/EG=0.2) exhibited the best sinterability and the highest oxide ion conductivity.
文摘Pr0.6-x NdxCa0.4 FeO3-δ （ x = 0.0, 0.2, 0.3, 0.4, 0.5, 0.6） were synthesized using Pechini method. A number of studies were conducted concerning composition, specific area, crystalline structure and microstructure of the samples by means of FT-IR, BET, XRD TG-DTA and SEM. The results show that all the samples with different doping amounts of Pr^3＋ and Nd^3＋ on A-site are fine dispersed, and mean particle size less than 100 nm. The powders have good sinterability, and the relative density is 95% after sintered at 1200 ℃ for 2 h. It is found that all specimens are entirely single phase solid solutions with orthorhombic perovskite structure, the stable perovskitetype phase is formed completely after calcination at 900 ℃.
基金This work was partially supported by a research grant fromAme Hisaharu Foundation,Toyama,Japan.
文摘Lead-free piezoelectric thin films of 0.055BaZrO_(3)–0.935(K_(0.45)Na_(0.5)Li_(0.05))NbO_(3)–0.01(Bi_(0.5)Na_(0.5))TiO_(3)(BZ–KNLN–BNT)were fabricated on(100)-LaNiO_(3)/SiO_(2)/Si substrates.The Pechini(polymeric precursor)method was carried out to prepare the complicated multi-component precursor solution.This method was suited for controlling the complex components accurately.The films crystallized at 700℃ showed a(100)pc-oriented perovskite structure,whose grain size was about 200 nm and thickness was about 700 nm.The Curie temperature Tc of the films was 292℃ that was near to that of the bulk ceramics.The preparation method used in this work provided a possibility for the application of multi-component lead-free piezoelectric films.
文摘The aim of the present work was to investigate the luminescent properties of europium-doped lanthanum aluminate (LaAlO3) powder prepared by Modified Pechini (MP) method. Samples were prepared at different Eu3+ concentrations and calcined at 1600°C. Structural and morphology characterizations were obtained by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscope (TEM). Luminescent properties were analyzed by photoluminescence (PL) and thermoluminescent phenomena. The XRD pattern shows pure lanthanum aluminate oxide LaAlO3 with a rhombohedral structure. Photoluminescence studies of the powders was related to 4f → 4f(5D0 → 7Fi) (i = 1, 2, 3, 4) transitions of Eu3+ ion, the most intense emission of Eu3+ in LaAlO3 was registered for the transition 5D0 → 7F1, for 5% of Eu3+. The recorded TL glow curves of excited samples showed a main TL peak, the main peak appeared its maximum as a function of excitation energy. The investigation demonstrates that polycrystalline LaAlO3:Eu3+ powders calcined at 1600°C have interesting luminescent characteristics.
文摘为开发高性能车载NO_2气体传感器敏感电极材料,以La_2O_3和Sr、Fe、Ni的硝酸盐、柠檬酸和乙二醇为原料,在pH=8～9的碱性条件采用Pechini法合成了约80～90 nm的复合氧化物(La_(0.8)Sr_(0.2))_2FeNiO_(6-δ)(LSFN)双钙钛矿粉末材料,并对合成工艺中柠檬酸(CA)与金属阳离子(M)的配比进行了研究。采用丝网印刷将其制备成基于氧化钇稳定氧化锆(YSZ)的NO_2传感器的敏感电极。运用TG/DTA、XRD、FSEM和ESEM对粉末材料和敏感电极进行了表征,并研究了烧结温度对LSFN敏感电极的NO_2敏感性的影响。研究结果表明:适当的柠檬酸与金属阳离子(CA/M)配比可降低材料的成相温度。XRD测试结果表明,LSFN的结构对称性会被烧结温度改变。对不同温度下烧结的LSFN敏感电极在550℃下的NO_2敏感性测试结果表明,其敏感性受烧结温度的影响,不同烧结温度下敏感电极形态可调控其NO_2敏感性。1300℃烧结的LSFN敏感电极的传感器具有较好的三维网络结构和最薄的电极厚度,表现出最高的NO_2敏感性,其灵敏度高达130. 17 m V/decade。
