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13477-34-4Relevant articles and documents
Synthesis and red luminescence of Pr3+-doped CaTiO3 nanophosphor from polymer precursor
Pan, Yuexiao,Su, Qiang,Xu, Huifang,Chen, Tianhu,Ge, Weikun,Yang, Chunlei,Wu, Mingmei
, p. 69 - 73 (2003)
Uniform and sphere-like nanoparticles of crystalline Pr3+-doped CaTiO3 have been prepared from complex polymer precursor at 600°C, in which, metal atoms are previously dispersed by citric acid in ethylene glycol solvent. The decomposition process of the precursor, crystallization, and particle sizes of CaTiO3 have been investigated by using thermal analysis, powder X-ray diffraction and transmission electron microscopy. Diffuse reflectance spectra, photoluminescence and decay curve indicate that a strong red emission located at the nearly NTCS ideal red site is deduced from the energy transfer from the band gap absorption to doping Pr3+ ions. The thermoluminescence curves exhibit that a potential long phosphorescent material based on Pr3+-doped CaTiO3 will be explored in future.
Borchardt, H. J.,Thompson, B. A.
, p. 5630 - 5632 (1960)
Ewing, W. W.,Krey, N. L.,Law, H.,Lang, E.
, p. 1958 - 1962 (1927)
Particle size dependence on the structural, transport and optical properties of charge-ordered Pr0.6Ca0.4MnO3
Kumar, Satyam,Dwivedi,Lourembam,Kumar, Shiv,Saxena,Ghosh,Chou,Chatterjee, Sandip
, p. 1094 - 1101 (2015)
Abstract Structural, transport and optical properties of nano-crystalline Pr0.6Ca0.4MnO3 have been investigated to emphasize on the semiconducting properties of charge-ordered manganite. Rietveld refinement of X-ray diffraction pattern of Pr0.6Ca0.4MnO3 nanoparticles show that due to increase in sintering temperature, MnO6 octahedra elongated along z-direction and compressed in x-y plane. Both Mn-O-Mn angles are found to decrease with increasing sintering temperature. Fourier transform infrared (FTIR) spectroscopy measurements reveal that the stretching and bending vibration of Mn-O-Mn is responsible for the change in Mn-O-Mn bond length and bond angle respectively. With increasing sintering temperature, these vibrations tend to increase, which resulted in the further distortion of MnO6 octahedra. Magnetic measurements suggest that charge ordering is established and system becomes antiferromagnetic with increasing particle size. Resistivity behavior of Pr0.6Ca0.4MnO3 nanoparticles clearly exhibit semiconducting nature of these systems, which is due to the formation of charge-ordered state of Mn3+ and Mn4+. Estimated optical band-gap of ～3.7 eV for Pr0.6Ca0.4MnO3 nanocrystals, makes it a potential candidate for wide band-gap magnetic semiconductors.
Rasulic, G.,Jovanovic, S.,Milanovic, Lj.,Petkovic, D.
, p. 661 - 670 (1987)
Synthesis of pure cementitious phases by sol-gel process as precursor
Stephan, Dietmar,Wilhelm, Patrick
, p. 1477 - 1483 (2004)
Calcium silicates and aluminates are the main constituents of ordinary Portland cement (OPC) and calcium aluminate cements (CAC) and therefore the pure phases are of great importance for the investigation of interactions between binder and additives or admixtures. Additionally, investigations on clinker phases doped with foreign ions enable the improvement of the performance of cements. For this purpose great amounts of pure phases are needed. These phases are hard to synthesize via a solid state reaction of solid educts. Thus there is a need for a new, more efficient route to synthesize these phases. The sol-gel process as precursor provides an alternative to the conventional method. In this paper experimental evidence is presented for an improved synthesis of calcium silicates and aluminates via sol-gel processes, the characterisation of these clinker phases and their hydration behaviour.
Structural and optical characterization of Eu and Dy doped CaWO4 nanoparticles for white light emission
Kaur, Puneet,Khanna, Atul,Singh, M. N.,Sinha, A. K.
, (2020)
The structural and light emission properties of calcium tungstate (CaWO4) nanoparticles containing Eu3+ and Dy3+ are studied. CaWO4 nanoparticles were prepared by chemical routes followed by drying at 80°C, doping with 1, 3, 5, 7 and 10 mol% of Eu2O3 and/or Dy2O3 and final annealing at 800oC. The samples were characterized by field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), synchrotron X-ray diffraction (XRD), Raman and photoluminescence (PL) spectroscopy. FE-SEM studies show that CaWO4 sample dried at 80°C contains spherical particles of diameter ～5 μm, and upon annealing at 800°C, dense and irregular shaped structures are formed. EDS mapping found a uniform distribution of Eu and Dy ions and only a small segregation in the CaWO4 matrix is observed. XRD studies revealed the co-existence of the tetragonal CaWO4 and cubic Dy2O3 and/or Eu2O3 phases in the doped samples and rule out the replacement of Ca2+ by rare-earth ions. The structural parameters: crystallite size, lattice strain, unit cell dimensions, atomic position coordinates, bond-lengths, bond-angles and cation-oxygen coordination numbers were determined. The short-range structure of CaWO4 consists of interconnected CaO8 and WO4 units. All the W–O bonds in WO4 units have the same length whereas two types of Ca–O bond-lengths exist in CaO8 units. The undoped CaWO4 sample annealed at 800°C, has the smallest Ca–O bond-lengths and unit cell dimensions due to the compressive macrostrain induced by heat-treatment. On incorporating Eu3+ and Dy3+, the W–O and Ca–O bond-lengths increase slightly. Raman spectra of all the samples are similar and show W–O vibrational modes. PL studies found that the undoped CaWO4, Eu and Dy-doped CaWO4 samples emit blue, red and yellow light respectively. The co-doped sample: 2 mol% Eu2O3–5 mol% Dy2O3–CaWO4 was closest to the ideal white light emission properties.
Synthesis & characterization of Dy and Ca Co-doped ceria based solid electrolytes for IT-SOFCs
Tanwar, Khagesh,Jaiswal, Nandini,Kumar, Devendra,Parkash, Om
, p. 683 - 690 (2016)
Numerous compositions in the system, Ce1-x-yDyxCayO2-δ have been synthesized using citrate-nitrate auto-combustion route. Samples sintered at 1350 °C for 4 h have density more than 93% of the theoretical value. Single phase formation has been confirmed by X-ray diffraction in all the samples. Reitveld refinement has been carried out to confirm the cubic fluorite structure with space group Fm3 m. Surface morphology of the sintered samples show the distinct grains and grain boundaries. Complex plane impedance analysis has been employed to separate the contribution of the grains, grain boundaries and electrode/specimen interface polarizations. A significant improvement in the electrical conductivity has been observed by partial replacement of Dy3+ with Ca2+ in Ce0.80Dy0.20O1.90 (keeping total number of oxygen vacancies fixed). Composition, Ce0.83Dy0.14Ca0.03O1.90 shows the highest conductivity, 1.45 × 10-2 S/cm at 600 °C. This value is about two orders of magnitude higher than that of singly Dy3+ doped ceria (6.01 × 10-4 S/cm) at the same temperature.
Weimarn, P. P. v.
, p. 89 - 89 (1908)
Purification of sphene concentrate to remove phosphorus impurity with dilute mineral acids
Nikolaev,Petrov,Pleshakov,Bychenya,Kadyrova
, p. 860 - 863 (2007)
Methods of crystal-optic, X-ray phase, chemical, and IR spectroscopic analyses were used to study the interaction of sphene and fluorapatite concentrates with dilute mineral acid solutions. The conditions under which the sphene concentrate can be purified