Synthesis And Characterization Of Rare Earth Phosphate Whiskers Via Solid State Reaction

Chapter One: Reseaches of rare-earth phosphate whisker have become a focus on nano-meterials. Rare-earth phosphate whiskers and theirs new developments on applications were reviewed in this chapter. The methods of synthesis and the growth mechanism formation explaining the mechanism of lanthanum phosphate whiskers were also introduced in this chapter. Research clew and meaning of this thesis were described.Chapter Two: The novel method for synthesis of lanthanum phosphate was studied, the target product was got successfully with Ammonium phosphate mono-basic and lanthanum nitrate as materials, and PEG-400 as template via low heat solid state reaction. Basis of the application of uniform experimental design as well as data mining technology, this paper took an experiment under different factors, established a mathematical model related the crystallite to the different factors by stepwise regression analysis. In this way it can gets the optimal synthesis process. The optimized synthesis process conditions were as follow: starting materials molar rate (La(NO₃)₃·6H₂O: NH₄H₂PO₄) was 1:1.3, time of grinding was 35min, warming of temperature was 50℃, time of warming was 10h. The product was characterized by TG/DTA and XRD. And the results indicated that the product was LaPO₄·0.5H₂O with size of 27.3nm and the crystallite is 93.53% under optimal synthesis process conditions.Chapter Three: The lanthanum phosphate whiskers were prepared by annealing a precursor powder at different temperatures and using different smelter flux. The precursor powders of lanthanum phosphate were synthesized at different template via low heat solid state reaction with Ammonium phosphate mono-basic and lanthanum nitrate as materials. The experimental results showed that: the products exhibit one-dimensional structure with average diameters 50～200 nm and lengths about 10～15μm. On the basic of the novel method for synthesis of lanthanum phosphate Whiskers, It can gets the optimal synthesis process data that as follows: The lanthanum phosphate Whiskers were prepared by annealing a precursors powder in the closed crucible at 1250℃for 2.5h using potassium sulfate as smelter flux. The precursor powders were synthesized with ammonium phosphate mono-basic and lanthanum nitrate as materials, and PEG-400 as template. This paper discussed the problem that why the lanthanum phosphate whisker has choice to the smelter flux and why the morphology of lanthanum phosphate whiskers is rod. Besides, this paper brought the growth mechanism formation forward to explain the mechanism of lanthanum phosphate whiskers.Chapter Four: On the basic of the optimal synthesis process for synthesis of lanthanum phosphate whiskers, The rare-earth phosphate whiskers including cerium phosphate whiskers, praseodymium phosphate whiskers, europium phosphate whiskers were prepared by annealing precursor powder in the closed crucible at 1250℃for 2.5h using potassium sulfate as smelter flux. The rare-earth phosphate precursor powders were synthesized with Ammonium phosphate mono-basic and rare-earth nitrate as materials and PEG-400 as template. On the studies, this parper discussed the problems that why the rare-earth phosphate whiskers have different morphology and what the photoluminescence property of rare-earth phosphates those were doped europium nitrate in the high temperature. In addition, this parper brought the growth mechanism formation forward to explain the mechanism of lanthanum phosphate whiskers.Chapter Five: On the basic of the optimalsynthesis process for synthesis of lightly rare-earth phosphate whiskers via solid state reaction, The heavy rare-earth yttrium phosphate whiskers were prepared by annealing yttrium phosphate nano-particles precursor powder in the closed crucible at 1250℃using potassium suifate as smelter flux. The whiskers of yttrium phosphate were smooth-faced, diameter existing a lowest limit, appeared few dislocation and fault. Based on these facts, the solid-liquid growth mechanism of the synthesis was suggested.