Preparation Of Polymer-Derived Blue Excited Europium-Containing Silicon Oxynitride Phosphor

Blue excited phosphors have received extensive attention due to high efficiencies of blue light chips.The europium(Eu),cerium(Ce),or praseodymium(Pr)-activated silicon oxynitride phosphors have been achieved by employing the polymer-derived method under mild conditions with simple preparation process,unfortunately,their excitation spectra are mainly limited in UV region.Therefore,it is meaningful to investigate how to prepare the blue excited silicon oxynitride phosphors by the polymer-derived method.In this work,we explored the conditions for preparing the blue excited silicon oxynitride phosphors by using polycarbonsilane(PCS),europium(Eu)-acetylacetonate and calcium(Ca)-acetylacetonate hydrate as raw materials.The effects of synthesis temperatures,sintering methods,sintering temperatures,and holding times were discussed.The process conditions for preparing the blue excited Eu-activated silicon oxynitride phosphors were determined.The effects of the initial atomic ratios of raw materials on the chemical compositions,phase structures,morphologies,and photoluminescence properties of the Eu-activated silicon oxynitride phosphors were compared.The microstructures for the blue excited phosphor with the strongest emission intensity were characterized.The excitation mechanism for the blue excited Eu-activated silicon oxynitride phosphors was discussed.It was found that to achieve the blue excited Eu-activated silicon oxynitride phosphors by the polymer-derived method,the initial atomic ratios of Eu/(Si+Ca)should be greater than 0.1/29 with non-zero Ca contents and the sintering temperature should be above 1550℃.By using the one-step sintering process with the holding time 3 h,and Eu/(Si+Ca)atomic ratio greater than 0.1/29,the phosphors with the initial atomic ratios of Eu/(Si+Ca)greater than 0.1/29 and non-zero Ca contents under blue excitation 468 nm were orange-red emitted(～600 nm)and yellow emitted(～570 nm)when they were sintered at 1650℃ and 1550℃,respectively.The emission intensity of the phosphors with the initial atomic ratios of Ca/Si being 1/12 increased as the increase of the initial atomic ratios of Eu/(Si+Ca).The emission intensity of the phosphors with the initial atomic ratios of Eu/(Si+Ca)being 1/29 increased first and then decreases as the increase of the initial atomic ratios of Ca/Si.The yellow phosphor(SiO0.42N0.89C0.03Ca0.12Eu0.06)synthesized at 320℃ and sintered at 1650℃ with the initial atomic ratios of Eu/(Si+Ca)and Ca/Si being 1/29 and 1/12,respectively,had the strongest emission intensity among all phosphors.It turned out that β-Si3N4 was the main phase for the blue excited Eu-activated silicon oxynitride phosphors prepared by the polymer-derived method when the initial atomic ratios Ca/Si were less than 1/12.Both of Eu and Ca ions were present in the single-crystallized particles with the β-Si3N4 phase.The joint action of the Eu ions and the alkaline earth metal Ca ions located at interstitials of β-Si3N4 was attributed to the appearance of the major blue excitation band for the blue excited Eu-activated yellow silicon oxynitride phosphor.