YPO[sub 4]:Ce Phosphor Sensitized by Thorium Ions

Awazu, Kenzo; Muto, Katsutoshi

doi:10.1149/1.2411817

Cited by 11 publications

(3 citation statements)

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“…Energy transfer also has been reported in which Ce +3 emission in YPO4 was sensitized by Th +4 (4). The work reported here shows the enhancement of both Ce +~ and Tb +3 emission in the presence of Th +4 in the monazite structure, in which the Th +4 does not have a direct role in the energy transfer in the ultraviolet region.…”

supporting

confidence: 70%

“…The luminescent properties of Ce +s and Tb +~ activation in the monazite structures LaPO4 and CePO4 have been described and the energy transfer from Ce + 3 to Ce +3 and Ce +3 to Tb +3 in these and other structures have been established (1)(2)(3). Energy transfer also has been reported in which Ce +3 emission in YPO4 was sensitized by Th +4 (4). The work reported here shows the enhancement of both Ce +~ and Tb +3 emission in the presence of Th +4 in the monazite structure, in which the Th +4 does not have a direct role in the energy transfer in the ultraviolet region.…”

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confidence: 94%

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Effect of Thorium on Ce+3 Phosphors

Hoffman

1971

J. Electrochem. Soc.

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The luminescent properties of Ce +s and Tb +~ activation in the monazite structures LaPO4 and CePO4 have been described and the energy transfer from Ce + 3 to Ce +3 and Ce +3 to Tb +3 in these and other structures have been established (1-3). Energy transfer also has been reported in which Ce +3 emission in YPO4 was sensitized by Th +4 (4). The work reported here shows the enhancement of both Ce +~ and Tb +3 emission in the presence of Th +4 in the monazite structure, in which the Th +4 does not have a direct role in the energy transfer in the ultraviolet region. ExperimentalTwo methods of preparation were used in these tests. Phosphors were prepared from cerium and lanthanum sources of 99.9% purity by co-precipitation of the composition from nitrate solutions with NaH2PO4-H20. When prepared from oxides of 99.999% purity, the oxides were mixed with (NH4)2HPO4 and fired initially at 300~ Final firing for both methods was 1000~ for several hours.Spectral distribution curves, excitation data, and decay measurements were obtained by methods which have been described previously (5). Reflectance measurements were made on a Cary 14, using BaSO4 as a reference standard. ResultsThe Ce +3 emission in CePO4 and LaPO4 matrices is a double band, peaking at 320 and 340 nm, resulting from the splitting of the group state, 2F5/2 and 2F7/2 ( Fig. 1). Green emisison is present when Tb +3 is incorporated in CePO4, but is very weak in the LaPO4 matrix unless Ce +3 is also present. * Electrochemical Society Active Member.

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confidence: 70%

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confidence: 94%

Effect of Thorium on Ce+3 Phosphors

Hoffman

1971

J. Electrochem. Soc.

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“…shorter than reported previously for Ce z+ phosphors. Awazu and Muto (2) described sensitization of YPO4-Ce by the incorporation of thorium ions, leading to a higher photoluminescent efficiency.…”

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confidence: 99%

Fast-Decay Phosphors

Bril

Blasse

Poorter

1970

J. Electrochem. Soc.

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Decay times, efficiencies, and spectral energy distributions of a number of Ce3+-aetivated phosphors have been determined. Decay times as short as 25-30 nsee are found for YPO4-Ce, YOC1-Ce, and YA13B4OI2-Ce; the two first-named phosphors show a weak, the last a strong, afterglow. The techniques of measurement have been described.Ce3+-activated phosphors are known as phosphors with very short decay times. The emission is ascribed to a 5d -> 4f transition in the Ce ~+ ion. The decay time is found to be shorter than 100 nsec due to the fact that an allowed transition is involved. Recently Ropp (1) summarized the results previously obtained and gave new data on Ce3+-activated rare earth phosphates. The decay times of the latter phosphors are about 30 nsec, i.e. shorter than reported previously for Ce z+ phosphors. Awazu and Muto (2) described sensitization of YPO4-Ce by the incorporation of thorium ions, leading to a higher photoluminescent efficiency.The emission band of Ce~+-activated phosphors has a doublet character due to the splitting (~2000 cm -1) of the ground state (2FT/2,2Fs/2). The emission is nearly always located in the blue or ultraviolet region of the spectrum. An exception is the yellow emission of the phosphor Y3A15012-Ce which has been recently described (3).In this paper, decay times, efficiencies, and spectral energy distribution of the emissions are given for several Ce 3 +-activated phosphors, especially yttrium, scandium, and lanthanum phosphates and borates and yttrium oxychloride.The cerium-activated phosphors find application in: (a) Flying-spot cathode-ray tubes for the TV transmission of films and slides. For color TV, an emission is required covering the whole visible spectrum. (b) A special type of color-TV receiving tube, the so-called index tube where an ultraviolet emitting phosphor is required in order to obtain the index signal (4). ExperimentalThe preparation of the phosphors has been described by us earlier (5). The cerium concentration is 1-2%.The decay times are measured both with ultraviolet and cathode-ray excitation. With cathode-ray excitation, a square pulse of voltage is displayed to the grid of the electron gun of a demountable cathode-ray tube, so that the phosphor can be irradiated during a variable time and with a variable repetition frequency. The method is analogous to that described previously by Bril and Klasens (4), but now much shorter times can be measured due to the use of a square-wave oscillator giving short pulses with a very short rise time (Tektronix Type 109, rise time 0.25 nsec, repetition frequency 550-720 pulses/sec) in combination with an oscilloscope with a wide frequency band (Philips No. 3330, bandwidth 70 MHz). The oscilloscope pictures were photographed with the aid of a Polaroid camera. To find all decay components, it is necessary to irradiate the phosphor with a wide range of excitation times in succession. Suppose a short and a long decay time component of equal efficiency are present, of e.g. 50 nsec and 1 msec. When the phosphor is then ir...

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