Structure and Morphology of ACEL ZnS:Cu,Cl Phosphor Powder Etched by Hydrochloric Acid

Withnall, Robert; Silver, Jack; Ireland, Terry G.; Fern, George R.; Marsh, Paul

doi:10.1149/1.3207950

Cited by 11 publications

(16 citation statements)

References 27 publications

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“…The symmetry is broken in the perpendicular direction to the major axis, there is no symmetry element such as a mirror or twofold rotational axis perpendicular to the major axis and crystal faces at the top of the crystal are not repeated at the bottom; this produces a hemimorphic crystal. As mentioned previously 8 hydrochloric acid etched ACEL ZnS:Cu particles revealed that a hemimorphic structure is present below the surface topology, an example is shown in the FESEM study shown in Figure 2. Hydrochloric acid etching of the ACEL ZnS:Cu particles allowed a facile evaluation as to the exact orientation of all individual particles relative to an applied electric field and the nature of the emitted light using low magnification optical microscopy imaging.…”

Section: Resultssupporting

confidence: 66%

Studies on the Orientation of ACEL ZnS:Cu Particles in Applied AC Fields

Ireland

Silver

2013

ECS J. Solid State Sci. Technol.

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In the last sixty years the understanding of the mechanisms of alternating current electroluminescence (ACEL) in transition metal-doped zinc sulfides, in particular ZnS:Cu particles has been the goal of all workers in the field. An in depth understanding of the crystallography and uncommon hemimorphic nature of these particles has lead to some understanding as to mechanism of light emission under an alternating current field. Hydrochloric acid etching of ZnS:Cu particles has allowed an intimate study of the hemimorphic nature and high density of planar stacking faults present in the particles that are critical for ACEL to occur. This work using complimentary field emission scanning electron microscopy and digital optical microscopy shows that the alignment of the planar stacking faults of these particles relative to the applied electric field is critical for light emission. Perpendicular alignment of the stacking faults results in no emission of light; as the alignment gradually approaches parallel emission increases and at parallel reaches a maximum. Thus, for devices using these materials alignment of the particles with the electric field is most important to maximize light output.

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Section: Resultssupporting

confidence: 66%

Studies on the Orientation of ACEL ZnS:Cu Particles in Applied AC Fields

Ireland

Silver

2013

ECS J. Solid State Sci. Technol.

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“…On the contrary, other authors in a recent study report large solubility of Cu in ZnS, albeit in the presence of stacking faults, as visualized by HRTEM [22]. Stacking faults seem to be present in all efficient AC-EL phosphors, which has been confirmed very recently by the investigation of etch patterns [23]. On this background, it seems reasonable, that milling procedures play a crucial role in phosphor fabrication [24].…”

Section: Materials For Ac-electroluminescencementioning

confidence: 97%

Materials for Powder-Based AC-Electroluminescence

Bredol

Dieckhoff

2010

Materials

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At present, thick film (powder based) alternating current electroluminescence (AC-EL) is the only technology available for the fabrication of large area, laterally structured and coloured light sources by simple printing techniques. Substrates for printing may be based on flexible polymers or glass, so the final devices can take up a huge variety of shapes. After an introduction of the underlying physics and chemistry, the review highlights the technical progress behind this development, concentrating on luminescent and dielectric materials used. Limitations of the available materials as well as room for further improvement are also discussed.

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“…A crucial feature of the ZnS:Cu phosphors is that Cu has a very low solubility in ZnS and forms conducting Cu x S precipitates in the insulating ZnS host above Cu concentrations of order 400-500 ppm. These precipitates form as the crystal cools and transforms into the cubic sphalerite phase-the stable phase at room temperature [2,5,6] and the phase with the best EL [7]. Although some early papers assumed the defect was Cu 2 S [8], we showed recently that at the nearest neighbor level, the main Cu x S defect is close to that of CuS and quite different from Cu 2 S [9].…”

Section: Introductionmentioning

confidence: 99%

Degradation and rejuvenation studies of AC electroluminescent ZnS:Cu,Cl phosphors

Stanley

Jiang

Bridges

et al. 2010

J. Phys.: Condens. Matter

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We report detailed degradation and rejuvenation studies of AC electroluminescence (EL) of the phosphor ZnS:Cu,Cl, aiming to better understand the physical mechanisms that control EL emission. We find that the AC EL emission spectra vary considerably with the AC driving frequency but all spectra can be fit to a sum of four Gaussians. During degradation, although there is a large overall decrease in amplitude, the shape of the emission spectra measured at a given AC frequency does not change. Annealing the samples after they are significantly degraded can rejuvenate the phosphors with a maximum rejuvenation occurring (for fixed annealing times) near 180 °C. Further, these test cells can be degraded and rejuvenated multiple times. However studies at slightly higher annealing temperatures (240 °C) show significant thermal degradation and, perhaps more importantly, a change in the spectral shape; this likely indicates that two distinct mechanisms are then operative. In extended x-ray absorption fine structure (EXAFS) experiments we find that the CuS nanoprecipitates in the ZnS host (∼ 75% of the Cu is in the CuS precipitates) do not change significantly after the 240 °C anneal; these experiments also provide a more detailed comparison of the local structure about Cu in pure CuS, and in ZnS:Cu,Cl. In addition, the EXAFS experiments also place an upper limit on the fraction of possible interstitial Cu sites, proposed as a blue emission center, at less than 10%. The combined experiments place strong constraints on the mechanisms for degradation and rejuvenation and suggest that EL degradation is most likely caused by either Cu or Cl diffusion under high E-fields, while thermal diffusion at slightly elevated temperatures without E-fields present, re-randomizes the (isolated) dopant distributions. Higher T anneals appear to damage the sharp tips on the precipitates.

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Structure and Morphology of ACEL ZnS:Cu,Cl Phosphor Powder Etched by Hydrochloric Acid

Cited by 11 publications

References 27 publications

Studies on the Orientation of ACEL ZnS:Cu Particles in Applied AC Fields

Studies on the Orientation of ACEL ZnS:Cu Particles in Applied AC Fields

Materials for Powder-Based AC-Electroluminescence

Degradation and rejuvenation studies of AC electroluminescent ZnS:Cu,Cl phosphors

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