螢光粉早期應用在日光燈、霓虹燈等,以及後來備受矚目的電子顯示器,近年來因為綠色能源的興起,研究多以在白光LED的照明設備上為發展,因此,本研究以溶膠-凝膠法(Sol-Gel Method)製備YVO4及YVO4摻雜Eu3+螢光粉體,探討其粉末合成及其光激發螢光性質。以溶膠-凝膠法製備之YVO4粉末,由DSC及DTA-TGA分析結果顯示,其結晶溫度約在500℃,其結晶活化能約為207.251 kJ/mol。另外根據XRD之分析結果顯示,當煆燒溫度從500℃增加至1200℃時,YVO4並沒有第二相的生成,最佳煆燒條件為800℃,3個小時,晶粒成長活化能約為21.127 kJ/mol。 另外在YVO4摻雜Eu3+離子部分,當煆燒溫度在800℃時,Eu3+離子摻雜量從1 mol%增加至50 mol%時,從XRD結果顯示並無第二相生成。而激發光譜顯示(Y1-xEux)VO4螢光粉體在250~350 nm間出現寬廣之激發帶為Eu3+離子由7F0 → 5H6 的電子躍遷吸收。(Y1-xEux)VO4在318 nm 光源激發下,發光光譜顯示主要放射波長在618 nm位置,來自於5D0→7F2的電偶極能階躍遷,活化中心離子Eu3+在主體晶格中佔據於非對稱中心位置。並且當Eu3+離子濃度增加到10 mol%時,可得到一最佳的發光強度,其CIE色度坐標位於x = 0.6627;y = 0.3367,為一發明亮紅光之螢光粉。由衰減曲線呈現單一指數遞減可知,代表只有一種發光機制,能階的躍遷並沒有發生交互緩解(Cross-Relaxation)的情形,是經由主體晶格先吸收能量,然後主體晶格再將能量以直接轉移的方式,將能量轉移至Eu3+離子的5H6激發態能階,激發態之Eu3+離子再以放光方式回至基態然後放光。濃度淬減效應則發生在Eu3+離子濃度為10 mol%,原因是由於Eu3+離子濃度增加時,使晶格扭曲嚴重而粉體結構變得鬆散,因此導致發光效率下降。
In order to reduce the volatility of vanadium, the sol-gel method is used to prepare the YVO4 and Eu3+-doped YVO4 phosphors. The YVO4 phase was formed at the beginning of 500℃and the optimum condition for YVO4 powders is calcined at 800℃ for 3 hr. The activation energy of crystallization and grain growth for YVO4 is ~ 207.251 kJ/mol and ~ 21.127 kJ/mol, respectively. In addition, europium-activated yttrium vanadate phosphor was synthesized by the sol-gel method. The precursor powders were heated at 800℃ for 3 hr to obtain the good crystallinity with better luminescence properties. XRD results indicate that there is not the second phase presented with increasing the Eu3+ ion concentrations up to 50 mol%. In the photoluminescent (PL) studies, excitation at 318 nm in terms of Eu3+ concentrations in YVO4 powders shows that the YVO4 phosphors display bright red luminescence at about 618 nm belonging to 5D0→7F2 electric dipole transition, and a weak band in the orange region of 5D0→7F1 transition at 594 nm. The time-resolved 5D0→7F2 transition presents a single exponential decay behavior revealing the decay mechanism of the 5D0→7F2 transition is a single decay component between Eu3+ ions only. The saturation of the emission intensity excited by intra-4f transitions occurs when the Eu3+ concentration is 10 mol% with a CIE color coordinate of x=0.6627;y=0.3367 Concentration quenching is active when x > 0.1.