Cl Phosphors Research Articles

An electrophoretic deposition process for screening phosphor powders for color displays

Abstract— A new process incorporating electrophoretic deposition and a photolithographic technique was developed for coating repeating triads of 75‐μm‐wide stripes composed of green ZnSiO4:Mn (P1), red Y2O3:Eu (P56), and blue ZnS:Ag, Cl (P11) phosphor particles. The resolution of the screens produced is 100 triads of phosphor stripes per inch of substrate. SEM micrographs show a high degree of phosphor stripe edge precision with relatively little cross‐contamination. Cathodoluminescence measurements revealed that the chromaticity of the phosphors were not altered by the coating process.

Effect of zinc metal addition on microstructural evolution of Zn 0.22 Cd 0.78 S$ phosphors studied by transmission electron microscopy

The effect of zinc powder addition on the microstructural evolution of fine Zn0.22Cd0.78S:Ag$, Cl phosphor particles was investigated in relation to the luminescent property of phosphors. The phosphor microstructures were analyzed by high-resolution transmission electron microscopy (HRTEM) using the ultramicrotome technique for specimen preparation. The phosphor baking process at 480 °C for 30 min in air results in significant damage to the surface structure of the phosphors due to the decomposition and oxidation of the phosphor itself. The addition of zinc metal powders into the Zn0.22Cd0.78S$ phosphors suppresses the oxidization and decomposition of phosphors by oxidizing zinc metal during the baking process in air. The oxidation of the zinc powders during baking provides the baking furnace with less oxidizing atmosphere for phosphor particles. The structure of phosphors, especially at the surface region, is much less degraded compared to the phosphors baked with no zinc metal addition. © 2000 Kluwer Academic Publishers

The difference in degradation behaviour of ZnS:Cu,Al,Au and ZnS:Ag,Cl phosphor powders

Auger electron spectroscopy (AES) and cathodoluminescence (CL) measurements showed that surface reactions with the consequent loss of CL intensity occur for both the ZnS:Cu,Al,Au and ZnS:Ag,Cl phosphor powders during prolonged electron bombardment. Although ZnO layers formed on both the ZnS phosphor surfaces there is a difference between the degradation behaviour of these two phosphors. Surface charging occurs during electron bombardment of the aged ZnS:Ag,Cl phosphor due to the formation of a non-conductive ZnO surface layer. Charging of the ZnS:Ag,Cl phosphor resulted in a delay in the surface reactions and to an increase in the CL degradation rate due to band-bending. A much slower degradation in CL intensity was measured for ZnS:Cu,Al,Au, where no charging occurred.

Blue CuxS coated ZnS:Ag,Cl phosphor as potential field emission display material

The ZnS:Ag,Cl phosphor shows a blue luminescence due to electron–hole recombination at donor–acceptor pairs. Ag dopant acts as the acceptor and Cl co-dopant acts as the donor. For conductivity treatment, the CuxS conductive layer is coated on the particle’s surface of ZnS:Ag,Cl by a wet chemical reaction. The low voltage phosphor film is prepared by sedimentation. Analyses by x-ray diffraction patterns and scanning electron microscopy photographs observe a preferential orientation phenomenon of the phosphor film. Electron probe microanalysis reveals that the Cu ions in the CuxS coated ZnS:Ag,Cl are homogeneously distributed. For CuxS coated at room temperature, the luminance intensity of the phosphor film is increased with the coating time and coating solution concentration. However, the luminance of phosphor film will degrade due to the oxidized phosphor’s surface. A proper heat treatment enhances the luminance of the phosphor film. A high luminance is observed from the CuxS coated ZnS:Ag,Cl phosphor and it is compatible for field emission display applications.

Low voltage cathodoluminescent properties of phosphors coated with In 2O 3 by sol-gel method

The phosphors used in usual CRTs are difficult to be used in a lower voltage than 500 V, because of charging-up on their surfaces. ZnS:Ag, Cl phosphor was coated with In 2O 3 using indium- iso-propoxide by the sol-gel method. It was found that a very thin In 2O 3 conductive layer could be coated uniformly on the phosphor surface. The low voltage cathodoluminescent properties were studied and compared with those without In 2O 3. The luminance of the phosphor excited with an electron beam of lower voltage than 500 V was considerably improved. Moreover, it was found that the formation of the thin layer is also quite effective for the improvement of the aging characteristics of cathodoluminescence.

Cathodoluminescent properties of Zn1−xCdxS:Ag, Cl phosphors including In2O3 excited by low‐energy electrons

Abstract— Low‐voltage cathodoluminescent properties of Zn1−xCdxS:Ag, Cl solid‐solution phosphors mixed with In2O3 conductive powder with a ratio of 10 wt.% have been investigated in view of the development of field‐emission displays (FEDs). Luminance of the mixed phosphor was higher than that of the phosphor without In2O3 at excitation voltages lower than 350 V. It was shown that the red luminance of Y2O2S:Eu phosphor with In2O3 is observed to be about four times that of Zn0.28Cd0.72S:Ag, Cl phosphor, which emits red, with In2O3 at 50–500 V.

Blue-Green Emitting SrS:Ce, Cl Thin-Film Electroluminescent Devices Prepared by Reactive Evaporation Using H2S Gas

SrS:Ce, Cl phosphor films were deposited by evaporating Sr metal and CeCl3 in H2S gas. The crystallinity, luminance, and emission spectra of the films were investigated in relation to the deposition conditions. X-ray diffraction intensity from the (200) plane of the SrS films was found to increase with the substrate temperature when the H2S pressure was kept constant, and had the maximum value at the H2S pressure of 1×10-2 Pa when the substrate temperature was kept constant. The variation of luminance in relation to the H2S pressure and the substrate temperature was similar to that of the (200) diffraction intensity. The luminance of 600 cd/m2 and the maximum emission efficiency as high as 1 lm/W were obtained at 1 kHz 30 µs wide ac pulse excitation for the films deposited at 600°C and H2S pressure of 1×10-2 Pa, although the emission color was not blue but whitish green.

Valency and solubility limit of Cu ions in cubic and hexagonal phases of ZnS:Cu:Mn:Dy(Cl) phosphors

Polycrystalline ZnS:Cu:Mn:Dy (Cl) phosphors with varying concentration of Cu and fixed concentrations of Mn and Dy have been prepared, XRD studies showed that the cubic — hexagonal phase transformation in the phosphors is a sensitive function of Cu concentration so that cubic phase dominates at higher Cu concentrations. It has also been found that Cu enters into the cubic ZnS phase as Cu+ while in hexagonal ZnS phase as Cu2+ and their solubility limits are around 0.1 wt.% and 0.25 wt.% respectively. Attempt has been made to confirm the existence of Cu+ in cubic phase and Cu2+ in hexagonal phase from EL emission spectra of the phosphors.

Cubic → hexagonal phase transformation in ZnS:Mn:Cu(Cl) phosphors

From the XRD studies of ZnS:Mn:Cu and ZnS:Mn:Cu(Cl) phosphors, it has been found that Mn 2+ does not play an independent role but incorporation of Cl - ions stimulates the cubic to hexagonal phase transformation so that the hexagonal phase increases with Cl - concentration in ZnS:Mn:Cu(Cl) phosphors. An attempt has been made to explain the role of Mn 2+ and Cl - ions in the mechanism underlying the phase transformation.

Effect of copper on β-α phase transformation in ZnS:Mn:Cu:Dy(Cl) electroluminophors

Electroluminescent polycrystalline ZnS:Mn:Cu:Dy(Cl) phosphors with different concentrations of Cu + and fixed concentrations of Mn 2+ and Dy 3+ have been prepared. The β—α phase transformation is found to be hampered by copper addition. The results obtained are explained on the basis of the effect of incorporation of Mn 2+, Dy 3+, Cu + and Cl − ions on creation of Zn-vacancies and subsequent atomic rearrangements. An attempt has been made to correlate the β—α phase transformation with EL brightness and microstructure.

High-energy emission band nature in ZnS-type phosphors activated with silver and chlorine

The cathodoluminescence emission spectra of cubic blue-emitting ZnS:Ag, Cl, hexagonal green-emitting (Zn0.675, Cd0.325) S:Ag, Cl as well as hexagonal red-emitting (Zn0.27, Cd0.73) S:Ag, Cl phosphors have been measured at 293, 77 and 4.2 K. The measured spectra of the phosphors exhibited a single broad emission band at 293 K, while they had two emission bands at 77 and 4.2 K. The two emission bands shifted to a lower energy with increase of their corresponding half-widths as the temperature at which the spectra were measured was raised. The time-resolved emission spectra measured showed that the low-energy band also shifted in the lower energy direction during the decay of luminescence, confirming its donor-acceptor (DA) transition nature. The high-energy band decayed faster than the low-energy one and no energy shift occurred during its decay; it was attributed to donor-isoelectronic pair (DI) transition. The lifetimes of 0.625 and 4.2 µsec were estimated for high- and low-energy bands, respectively, in the emission spectra of ZnS:Ag, Cl at 4.2 K.

A study of the white electroluminescence in ZnS:Cu,Pr,Cl phosphors

The method of preparation of ZnS phosphors doped with praseodymium and copper is given. The electroluminescence (EL) spectrum of ZnS:Pr,Cl has two broad bands at 470 and 570 nm. ZnS:Cu,Pr,Cl gives white emission with spectral peaks at 470, 520, 570 and 640 nm. The EL spectra of both types of phosphor exhibit a conspicuous colour shift as the frequency of the excitation voltage is varied. Detailed investigations show that the relative intensities of spectral peaks are strongly dependent on the frequency of the excitation voltage. The colour shift is explained on the basis of the Schon-Klasens model.

Effect of chlorine concentration on the spectral characteristics of electroluminescence in ZnS: Cu: Cl phosphor

ZnS: Cu: Cl phosphor prepared under a vacuum firing process is found to give blue electroluminescence with emission peak at 460 nm which remains unaltered with the frequency of the excitation voltage. Addition of excess chlorine in the phosphor gives blue, green and red emission at 460, 520 and 640 nm. The intensity of the blue band decreases and it finally disappears as chlorine concentration is increased. A scheme involving three energy levels attributed to Cu 2+, Cu + and Cl - centres in ZnS explains the experimental results completely.

D - A recombination luminescence in (Zn, Cd)S DCEL powder cells

DCEL powder cells containing ZnS:Cl or (Zn, CdS)Ag, Cl phosphors exhibit D - A recombination luminescence when excited by unipolar pulses. The emission follows and preceeds the voltage pulse and arises from the detrapping of electrons created by the avalanche process. From the temperature dependence of efficiency and thermoluminescence, electron trap depths of 0.36 and 0.41 eV were deduced for ZnS:Cl and ZnS:Ag respectively. The efficiency of recombination can be increased by following the ionisation pulse with a pulse of lower amplitude but opposite polarity. Power efficiencies of 0.005% (blue), 0.008% (green) and 0.001% (orange) were found for (Zn, Cd)S Ag phosphors.

Preparation and Properties of ZnS:Ag, Cu, Cl Phosphor Powder Emitting Blue Electroluminescence

Preparation and Properties of ZnS:Ag, Cu, Cl Phosphor Powder Emitting Blue Electroluminescence

Effect of charged imperfections on electroluminescence of the ZnS:Cu,Cl phosphor

Electroluminescence is very much dependent on the concentration of imperfections created inside the host crystal. The effect of imperfections in ZnS:Cu,Cl is considered for different temperatures and compared with experimental curves. The resemblance supports our theoretical approach, i.e. the impact ionisation mechanism. The phosphor is most sensitive in the concentration range 10 17 to 10 19 per cm 3.

Thermoelectronic mechanism of quenching the photoluminescence of ZnS ? Cl phosphors by an electric field

Results are presented of an investigation of the quenching of the photoluminescence of ZnS — Cl by an electric field as a function of the specimen temperature, the intensity of the exciting radiation, and the electric-field intensity. The experimental data are explained on the basis of a thermoelectronic quenching mechanism.

Effects of heat treatment in vacuum on some properties of ZnCdS � Ag � Cl phosphor

Effects of heat treatment in vacuum on some properties of ZnCdS � Ag � Cl phosphor

The effect of the concentration of activator on the radical-recombination luminescence of ZnS, Mn, Cl phosphors

The effect of the concentration of activator on the radical-recombination luminescence of ZnS, Mn, Cl phosphors

The mechanism of flare-up and extinction in ZnS ? Fe(Cl) phosphors

The mechanism of flare-up and extinction in ZnS ? Fe(Cl) phosphors