A Study on the Synthesis and Luminescent Properties of Novel Indates and Germanates Phosphors
Teng - Ming Chen
第二章及第三章：關於新穎場發射式顯示器（FEDs）用螢光體的開發。兩種主體晶格SrIn2O4及CaIn2O4的能隙分別為3.6 eV及3.9 eV，具導電性。傳統螢光體在低電壓使用時、電荷累積的問題可以得到解決。
第六章：研究n S 2 組態離子；也就是Bi3+（6 S 2）離子，在Ca2GeO4晶格的發光現象。多數Bi3+ 活化的螢光體在低溫放射，但本研究中的螢光體在室溫即放射可見光。與稀土離子相較，Bi3+ 離子的發光研究顯得相當稀少且不完整。在本文中，光譜均被詳細標記，並且詳述A帶放射的組態模式；A帶的放射機制以及"不規則放射"的機制。在Bi3+ 螢光體的簡短回顧中；Bi3+ 激發帶的位置，被發現與主體中、未被取代的陽離子的電負度有關。其關連性是第一次被提及。另外；文中也收錄以Eu3+、Pr3+及Tb3+離子做為活化劑時、相關的圖譜及圖表。
Several unprecedented inorganic phosphors of indates and germinates have been prepared via solid-state routes and their relevant luminescent properties were investigated in the present research. In the quest for new inorganic phosphors with great potential for modern displays applications and to gain a deeper insight into the luminescence for Pr3+ ( 4 f 2 ), Eu3+ ( 4 f 6 ), Tb3+ ( 6 f 8 ), and Bi3+ ( 6 s 2 ) activators, we have initiated investigations on phosphors with hosts such as semiconducting SrIn2O4 and CaIn2O4, insulating Sr2GeO4 and Ca2GeO4. Furthermore, the luminescence of self-activated Zn2GeO4 was also studied. The configurational coordinate diagrams and band structure for these indates and germanates have been adopted as an illustrative model to rationalize the observed photoluminescence emission and excitation spectra for Eu3+, Pr3+, Tb3+and Bi3+, in particular, the emissions attributed to Eu3+ activated Sr2GeO4 and Ca2GeO4 and Bi3+ activated Ca2GeO4 has been thoroughly analyzed and assigned using band structure model. Furthermore, these new phosphors have been characterized with X-ray diffraction (XRD) for phase identification and structure analysis, photoluminescence (PL) spectra for investigations of luminescent properties, and the diffuse reflectance (DR) spectra to understand energy absorption and band gap energy estimation. In addition, brightness and chromaticity coordinates and diagrams were also measured to characterize the chromaticity under ultraviolet excitation for the phosphors. Our research interests were also extended to a series of self-activated Zn2GeO4 phosphors whose presence and importance may have been overlooked for years in the literature. A mechanism for rationalization of self-luminescence from the host lattice has been proposed. Furthermore, the effects of synthetic conditions (i.e., temperature, atmosphere and duration of reduction), excitation wavelengths and, possibly, oxygen defects present in the host lattice on the luminescence for Zn2GeO4 phases. Consequently, the knowledge established on the basis of results from this work may open the door to the exploratory work into a completely new area in phosphor materials research.
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