Enhancement of Cathodoluminescent Characteristic from CaTiO 3 :Pr 3+ , by Ga 3+ Addition
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Enhancement of Cathodoluminescent Characteristic from CaTiO3:Pr3+, by Ga3+ Addition Jung-Woo Byun, Byung-Kyo Lee, Dong-Kuk Kim1, Seong-Gu Kang2, Seung-Youl Kang3 and Kyung-Soo Suh3 Dep. of Inorg. Mat. Eng., Kyungpook Nat’l Uni., 1370, Sankyuk-Dong, Puk-Gu, Taegu, 702-701, Korea 1 Dep. of Chem., Kyungpook Nat’l University, 1370, Sankyuk-Dong, Puk-Gu, Taegu, 702701, Korea 2 Dep.of Chem. Eng., Hoseo Uni., Asan, Chungnam, 336-795, Korea 3 Micro-electronics Lab., ETRI, 161, Kajong-Dong, Yusong-Gu, Taejon, 305-350, Korea ABSTRACT CaTiO3:Pr3+ as an oxide phosphor is expected to be applied for a field emission display(FED) due to its relatively high conductivity. For the practical use, however, the CL intensity of CaTiO3:Pr3+ has to be enhanced. We introduced Ga3+ as a co-activator into the phosphor and investigated the CL characteristics with various Ga3+ concentrations. The CL intensity of CaTiO3:Pr3+ was remarkably increased when Ti4+ atom was replaced by the Ga3+. When the Ga3+ concentration is 5 times of Pr3+ molar concentration, the emission intensity of the CaTiO3:Pr3+ phosphor with Ga3+ is about 5 times higher than Ga3+-free samples. So, it was concluded that the addition of Ga3+ is essential to enhance CL property at low voltage. We proposed the following mechanism that excitation into the host lattice leads to the formation of electrons in the conduction band and holes in the valence band. The electrons in the conduction band recombine with the holes trapped at Ga3+ and this energy is effectively transferred to Pr3+ ion, which gives its own characteristic red emission. INTRODUCTION Recently, field emission displays (FEDs) have been developed as next-generation flatpanel displays, which have replaced cathode-ray tubes (CRTs) and liquid–crystal displays(LCDs). The low voltage operation and high emission source of FED lead to high performance for FED[1]. So the development of new phosphors for FEDs is necessary. In 1994, a new red-emitting phosphor for FEDs, CaTiO3:Pr3+, was developed. This phosphor is highly regarded as a low-voltage red phosphor because of its good color quality and intrinsic conductivity. [2] In calcium titanates, one can expect efficient excitation processes through the conduction band (CB) of the host and/or the Pr3+ 4f5d band, followed by strong luminescence intensities due to non-centrosymmetric cation sites. G3.6.1
Considering the ionic size, Pr3+ is very probable to replace the Ca2+. Since the substitution of Pr3+ for Ca2+ will break the charge balance, it is necessary to add other ions with the oxidation state of +3 in the Ti4+ site. The Ga3+ is a good candidate for the co-dopant due to its similar ionic size (Ti4+ : 0.61
, Ga3+: 0.62 ) and its oxidation state. The similar behavior
was observed also for SrTiO3:Pr3+ of Al3+ addition [3-5] In this work, we investigated the luminescence characteristics of CaTiO3:Pr3+, Ga3+ phosphors and suggested the effect of Ga3+ on the luminescence properties. EXPERIMENTAL DETAILS The CaTiO3:Pr3+, Ga3+ phosphor samples were prepared by solid solid react
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