Electrochemical Luminescence of Rare Earth Metal Ion Doped MgIn[sub 2]O[sub 4] Electrodes

Abstract

Anodic dc electrochemical luminescence ͑ECL͒ property of nondoped and rare earth ͑RE͒ ion-doped MgIn 2 O 4 electrodes, famous as a transparent electronic conducting material, was investigated. Nondoped and Dy 3+ , Sm 3+ , Ho 3+ , Er 3+ , Eu 3+ , and Tm 3+ doped MgIn 2 O 4 , usually exhibiting no or very weak photoluminescence ͑PL͒, showed ECL under anodic polarization over 20 V. ECL luminescence can be attributed to that from the oxygen defect for nondoped MgIn 2 O 4 and to that from the doped emission centers ͑RE ions͒ for MgIn 2 O 4 :RE, respectively. Doped RE ions form solid solution within MgIn 2 O 4 host. From the Rietveld refinement analysis of X-ray patterns, we concluded that RE ions are located at the 16d site in MgIn 2 O 4 . The ECL intensity dependence on the Er 3+ ion concentration of MgIn 2 O 4 :Er 3+ showed a maximum at ͓Er 3+ ͔ = 2% and then decreased, whereas PL intensity monotonously increased with increasing Er 3+ concentration. These results suggest that electron conductivity of MgIn 2 O 4 host are also related with the ECL property.

Electrochemical luminescence of Mg1−xCaxIn2O4:Er3+ electrodes

“…In Fig. 1 [9]. According to the study of Kawazoe et al [14][15][16][17], about electron conduction mechanism in MgIn 2 O 4 , electrons move through In 3+ ion network (8a and 16d sites).…”

“…In the previous paper, on the basis of the X-ray and neutron diffraction data we have concluded ECL mechanism of MgIn 2 O 4 :RE electrodes as follows. The hot electrons injected via electrochemical reaction under the highly anodic polarization pass through In 3+ network (8a and 16d sites) and excite RE ion by the impact [9]. By exchanging Mg 2+ ion to Ca 2+ ion, slight local strains would be introduced to the host.…”

“…In the previous paper, we reported some rare-earth (RE) ion-doped MgIn 2 O 4 electrodes show bright ECL [9]. With the increase in RE ion concentration, ECL intensity shows a peak at 2%, then steeply decreased.…”

“…In the case of the ntype semiconductor, two types of ECL have been reported [1][2][3][4][5][6][7][8][9]. One is observed under the cathodic polarization and its luminescence originates from the recombination of electron-hole pairs with the aid of hole injection to the valence band of semiconductors by the oxidative electrolyte (e.g., S 2 O 8 2À or Fe(CN) 6 3À ) [1][2][3][4][5].…”

“…One is observed under the cathodic polarization and its luminescence originates from the recombination of electron-hole pairs with the aid of hole injection to the valence band of semiconductors by the oxidative electrolyte (e.g., S 2 O 8 2À or Fe(CN) 6 3À ) [1][2][3][4][5]. In the other mechanism, ECL can be obtained via the impact excitation by hot electrons injected into the n-type semiconductor under strong anodic polarization [6][7][8][9]: the latter mechanism is similar to the ECL device [10,11]. This anodic ECL on the surface of n-type semiconductor is suitable for exploring new ECL materials and optimizing the structure of the host material for similarity in the excitation mechanism.…”