Title: Y_2O_3: Re (Re = Nd, Er, Ce) nanopowders and transparent ceramic preparation and spectral properties ofAuthor: Wang pureDegree awarded: China University of Science and TechnologyKeywords: Y_2O_3: Nd;; Y_2O_3: Er;; Ce;; nano-powder;; transparent ceramicsSummary:
This paper contains the Neodymium Magnets chapters content, introduction describes the background work papers, the second chapter to Chapter IV reported Y_2O_3: Re (Re = Nd, Er, Ce) Preparation, characterization and luminescence properties of the results.
Introduction First introduced in recent years focusing on several types of rare earth luminescent materials, and details the characteristics of rare-earth ion and its light, given the development of transparent ceramics and related preparation process, and finally a brief introduction to solid-phase method, sol-gel method and nano powder prepared by coprecipitation of related content.
In the second chapter, respectively, by solid-phase method, sol-gel method and coprecipitation Y_2O_3: Nd powder, the powder XRD and SEM using the chemical structure and particle morphology characterization, and semiconductor laser with a 808nm excitation of the sample to study the structure of the sample under different methods of morphology and luminescence properties of the difference. Preparation of solid samples, simple operation, but the reaction required high temperature, 800 ℃ calcined under the due Nd ~ (3 +) ion is not had time to spread, the sample is almost no light; the preparation of the powder out of a larger particle size, and pores. Sol-gel samples, particles reunion is more serious and morphology to porous structure of the main complexing agent and metal complexation reactions affected by pH, different pH values to be different from the product of luminous intensity. Coprecipitation samples, get a smaller particle size, about 20 nm in particle dense knot sheet structure, with the basic conditions for preparation of transparent ceramics.
Further study of the different doping concentrations Y_2O_3: Nd nano-powder, and 808 nm lattice constant emission spectra under the excitation laser intensity changes with Nd concentration. When the doping concentration higher than 1%, the samples begin to light quenching, quenching by cross relaxation between the energy levels of the institution.
In the third chapter, with ammonium bicarbonate as the precipitant, changing preparation conditions, the use of coprecipitation Y_2O_3: Er ~ (3 +) nanopowders and transparent ceramics, by FTIR, elemental analysis, XRF and other means of chemical precursors structure and composition, by TG-DTA analysis of the precursors in the process of weight loss in the heating case, the powder XRD and SEM into the phase of the case and the particle morphology characterization. In-depth analysis of Er ~ (3 +) ion spectral characteristics, and pH effects on powder light. The experimental system will be made of ceramic powder samples, analysis of different conditions on ceramic precursor transparency effects, and analysis of the luminescence properties of ceramic powder and the similarities and differences.
pH value changes, the chemical structure of the precursors is essentially the same, but the sediment in Y, Er will change the ratio, pH value of 9.5 when the precursors of the actual content of Er pH 8.5 than at 0.5%, and nanoparticles obtained at different pH of the particle size and distribution vary, the resulting light-emitting properties of the samples differ.
1% added dispersant chemical structure of the precursor product had no effect, but it will change the Y, Er precipitation ratio; and dispersing agent in the different pH values is not the same impact on the powder particles, pH value 8.5, the product particles smaller, wider range of particle size distribution, the surface is very smooth sheet structure, pH value 9.0, the role of dispersant contrary, an increase in the surface debris.
Y_2O_3: 1% Er in the range of 300 ~ 800nm have characteristic absorption, corresponding to the 4f ground state to excited states of the 4f transitions. 380nm wavelength light excitation, the main emission peaks at 500 ~ 600nm range, corresponding to ~ 2H_ (11 / 2) / ~ 4S_ (3 / 2) → ~ 4I_ (15 / 2) transition, the strongest emission peak at 563nm. At 980nm and 808nm laser excitation, monitored on a sample of two-photon conversion green emission phenomenon; when Er doping concentration, the existence of ~ 4S_ (3 / 2) → ~ 4I_ (9 / 2) and ~ 4I_ (15 / 2) → ~ 4I_ (13 / 2) level of cross-relaxation between, so that the red emission enhancement. 980nm excitation, red is the two-photon upconversion process.
Ceramic samples with the XRD diffraction peaks are basically consistent powder samples, but the peak intensity distribution changes, (400) plane priority growth, resulting in the corresponding diffraction peak intensity greatly enhanced. pH and dispersant for ceramic have transparency effects, pH = 8.5 ceramics better transparency. After adding a dispersant, ceramic transparency is not the same degree of change, pH value of 8.0 and 8.5, the effect of dispersing agent is best; the same pH value, the excess dispersing agent hired by the opposite. After high-temperature sintering grain growth better, to enhance the light-emitting ceramic samples of about one order of http://www.everbeenmagnet.com/en/products/110-sintered-neodymium-magnets magnitude.
In the fourth chapter, with the co-precipitation method (Y_ (0.95) La_ (0.05)) _2O_3: Ce powder, analysis of samples of light-emitting properties of Ce and La ion impact.
The first X-ray diffraction results show that the introduction of the matrix in Y_2O_3 5% La does not change the basic structure of Y_2O_3 itself, solid solution (Y_ (0.95) La_ (0.05)) _2O_3 remains cubic phase. Excitation and emission spectra showed that the introduction of 5% La matrix and calcined at 800 ℃ obtained after the sample excitation in the UV 271nm/368nm have broadband emission in the visible band; with samples of different XPS Ce 3d spectra and analysis of O 1s spectrum can be determined from the light-emitting Ce ~ (3 +) ions, and further concluded that the introduction of La matrix on certain conditions, can Ce ~ (3 +) ions have a stabilizing effect.Degree Year: 2010
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