Phosphor Brightness

Let us suppose that we have prepared a series of phosphor compositions wherein the activator concentration was the variable. We would need to measure these samples to determine which concentration was near to the optimum. Let us further suppose that we wish to use our phosphor in a LPMV lamp application. Although we could manufacture a test-lamp, usually this is not very feasible. What we do is to prepare a thick layer on a holder and compare it to a standard phosphor having similar emission characteristics. The layer is called a plaque and the apparatus is called a plaque-tester , as shown in the following  

---

The explanation lies in the defect reactions controlling the formation of the phosphor itself. The defect reactions occurring were found to be the substitution of a trlvalent cation on a divalent site and the defects reactions thereby associated. This is shown in the following table which compares these two methods of preparing such materials. In this case, the increase in brightness was found to be related to the amount of activator actually being incorporated into the lattice. It is well known that phosphor brightness is proportional to the numbers of Sb3+ ions (activators) actually incorporated into cation sites of the pyrophosphate structure. 

Silver Phosphates. Silver phosphate [7784-09-0], or silver orthophosphate, Ag3P04, is a bright yellow material formed by treating silver nitrate with a soluble phosphate salt or phosphoric acid. Silver pyrophosphate [13465-97-9], is a white salt prepared by the addition of a soluble... 

Tankwater, Bright dip acid (phosphoric), Cyanide rinse hath, Pickle Liquor, Sodium AJuminate Liquor, N.S.S.C. Liquor, Kraft Liquor, Soda Liquor, Sulfite Liquor, Stillage, Corn Syrup, Gelatin, Salt, Soybean Oil, Steepwater, Sugar, Whey, Mercerizing Caustic, Nylon Salt, Rayon Spin Bath, and Sodium Sulfate. 

Chemical polishing, yielding a surface of high specular reflectivity, exploits fully optimised bright dip solutions often achieved by the further addition of phosphoric acid at the expense of the residual water. Because phosphoric acid is relatively viscous at lower temperatures (e.g. less than 40°C) it can act as diffusion layer promoter (C), but its presence increases the chemical costs considerably. 

Fluorescent lamps are manufactured by squirting a suspension of phosphor particles in an ethyl cellulose lacquer upon the inner surface of a vertical glass tube. Once the lacquer drains off, a film of peuticles is formed. The lacquer is then burned off, leaving a layer of phosphor particles. Electrodes are sealed on the tube is evacuated Hg and inert gas is added and the lamp ends are added to finish the lamp. Lamp brightness and lifetime are dependent upon the particle size distribution of the phosphor particles. The number of small particles is critical since they are low in brightness output... 

In this application of the log-normal plot, note that the "n chanical" separation of "fines" has created anew particle distribution with 62 = 2 p. Even the value of 02 differs from that of the major particle distribution. In the "fines" fraction, it appears that the largest pcirticle does not exceed about 5 p. Needless to say, lamps prepared from this phosphor were inferior in brightness. Armed with this information, one could then recommend that the method of "fines" removal be changed. 

Green emitting (547 nm) phosphor for display screens and color television, not quite as bright as Gd202S Tb3+... 

The future for the use of coordination compounds in phosphors looks very bright indeed. Man s need to illuminate his surroundings, transfer information, and display that information efficiently can only mean an ever more demanding and growing marketplace for materials that emit light. Coordination compounds are, and will remain, in widespread use as both precursors in phosphor synthesis and as major constituents in small molecule OLEDs. 

Some oxide-type minerals have been found to luminesce when irradiated. A simple example is ruby (aluminium oxide with chromium activator), which emits bright-red light. The phosphors are incorporated into colour television screens to emit the colours blue (silver-activated zinc sulphide), green (manganese-activated zinc orthosilicate), and red (europium-activated yttrium vanadate). 

---