Mn4+ doped and Gd3+, Lu3+ co-doped MgAl2\ud
Si2O8-based phosphors were first of all synthesized by solid\ud
state reaction at about 1300.0 C. They were characterized\ud
by thermogravimetry, differential thermal analysis, X-ray\ud
powder diffraction, photoluminescence, and scanning electron\ud
microscopy. The luminescence mechanism of the\ud
phosphors which showed broad red emission bands in the\ud
range of 610–715 nm and had a different maximum intensity\ud
when activated by UV illumination was discussed. Such a\ud
red emission can be attributed to the intrinsic 2E+ 4A2\ud
transitions of Mn4
Mn4+ doped and Pr3+,4+, Nd3+ co-doped MgAl2Si2O8-based phosphors were first of all synthesized about\ud
1300 8C. They were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray\ud
powder diffraction (XRD), photoluminescence (PL) and scanning electron microscopy (SEM). The\ud
luminescence mechanism of the phosphors, which showed broad red emission bands in the range of 610–\ud
715 nm and had a different maximum intensity when activated by UV illumination, was discussed. Such a\ud
red emission can be attributed to the intrinsic d–d transitions of Mn4+
Mn4+ doped and Eu3+, Yb3+ co-doped MgAl2\ud
Si2O8-based phosphors were prepared by conventional\ud
solid state reaction at 1,300 C. They were characterized\ud
by thermogravimetry, differential thermal analysis, X-ray\ud
powder diffraction, photoluminescence, and scanning\ud
electron microscopy. The luminescence mechanism of the\ud
phosphors, which showed broad red emission bands in the\ud
range of 600–715 nm and had a different maximum\ud
intensity when activated by UV illumination, was discussed.\ud
Such a red emission can be attributed to the\ud
intrinsic 2E + 4A2 transitions of Mn4+
The total conductivity (σ T ) in the β-phase and δ-Bi 2 O 3 doped with Tb 4 O 7 system was measured in the composition range between 1 and 30 mol% Tb 4 O 7 at different temperatures. According to the DTA/TG results, this tetragonal type solid solution was stable up to about ∼740 • C, and the solubility limit was found at ∼5 mol% Tb 4 O 7 in the β-phase; this fcc type solid solution was stable up to about ∼740 • C, and the solubility limit was found at ∼30 mol% Tb 4 O 7 in the δ-phase. All phases showed predominant oxide ionic conduction. It has been proposed that β-and δ-Bi 2 O 3 phases contain a large number of oxide anion vacancies and incorporated terbium cations at tetrahedral sites that affect the oxygen sublattice of the crystal structure.Keywords bismuth oxide, oxygen ionic conductivity, terbium oxide
INTRODUCTIONSolid electrolytes are the most important components of solid-state electrochemical devices, which are becoming increasingly important for applications in energy conversion, chemical processing, sensing, and combustion control. Bismuth oxide systems exhibit high oxide ionic conductivity and have been proposed as good electrolyte materials for applications such as solid oxide fuel cell and oxygen sensors. However, due to their instability under low oxygen partial pressure conditions there has been difficulty in developing these materials as alternative electrolyte materials compared to state-of-the-art cubic stabilized zirconia electrolyte. Bismuth oxide and doped bismuth oxide systems exhibit a complex array depending on dopant concentration, temperature, and atmosphere. [1][2][3][4][5] Six polymorphs of Bi 2 O 3 have been reported in the literature: monoclinic α-Bi 2 O 3 , tetragonal β-Bi 2 O 3 , cubic (bcc) γ -Bi 2 O 3 , cubic (fcc) δ-Bi 2 O 3 , orthorhombic ε-Bi 2 O 3 , and triclinic
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