**23. Spray pyrolysis**

The aerosol processing, for example spray pyrolysis, is Known as a promising technique, especially to prepare the multi-component oxides like the CaMgSi2O6:Eu (CMS) phosphor. **Fig. 27** shows a simplified schematic diagram displaying the whole preparation steps of CMS phosphor by the spray pyrolysis. An ultrasonic aerosol generator with six vibrators (1.7 MHz) was used to atomize the precursor solution and the produced droplets were carried by the air (45 L min−1) into a hot furnace with a quartz tube (length: 1200mm and inner diameter: 50 mm) at 900 ◦C. The formed particles were collected by a Teflon bag filter and posttreated at the temperature of 1000–1250◦C for 5 h under a reducing atmosphere (5% H2/N2 mixture gas) for crystallization and activation of divalent europium. To test the thermal degradation, the prepared CMS and commercial BAM samples were mixed with commercially available binder paste (Daejoo corporation) which is practically used for the formation of phosphor films in PDPs. Next, the phosphor paste, wherein the fraction of powder was 50 wt.%, was fired at 500 ◦C for 30 min in the air environment. The crystal phase of the prepared CMS particles and PL were then analyzed.X-ray storage phosphors based on BaFBr:Eu are also made using this technique.

Firing (sintering) is a necessary step for solid-state phosphor synthesis since activation energy must be supplied for the activators to go into the crystal structure of the host material. By solid-state reaction, conventional synthesis of phosphors takes many hours even with flux. Microwave processing is a relatively new technique and characterized by substantially accelerated reaction kinetics in the material systems if properly chosen. Using microwave processing, various phosphors have been synthesized. The high efficiency phosphors developed for field emission displays, plasma displays, and white light emitting diodes (LED) tend to be degraded by the operating environment and/or the devices' manufacturing conditions. Transparent oxide coating on phosphor powders is an effective approach to protecting phosphors from ageing, The coating can isolate the phosphor from the environment and could protect both the phosphor and the device. Microwave synthesis of some important phosphors and microwave processing of some phosphors coated with oxides are reported. In one study, microwave synthesis was carried out in a 2.45 GHz, 6 kW capability multimode microwave furnace with atmosphere controlled, although, only about 1 kW or less power was needed in the experiments. The powder sample (30-70 g each) was loaded in an alumina crucible, which was then placed in a properly insulated package with SiC as microwave susceptor. The insulation package was made of porous FiberFrax Duraboard 3000. The temperature of the sample was monitored with an optical pyrometer. The temperature was controlled by adjusting input power. During the microwave processing, the sample was rotating horizontally about the axis. The samples were microwave heated up and held at the designed temperatures for typically 10-20 min. The microwave-synthesized products were characterized for particle size, brightness, phase composition, morphology, luminescence emission, and color coordinates. Optimization of the parameters is required to achieve

The aerosol processing, for example spray pyrolysis, is Known as a promising technique, especially to prepare the multi-component oxides like the CaMgSi2O6:Eu (CMS) phosphor. **Fig. 27** shows a simplified schematic diagram displaying the whole preparation steps of CMS phosphor by the spray pyrolysis. An ultrasonic aerosol generator with six vibrators (1.7 MHz) was used to atomize the precursor solution and the produced droplets were carried by the air (45 L min−1) into a hot furnace with a quartz tube (length: 1200mm and inner diameter: 50 mm) at 900 ◦C. The formed particles were collected by a Teflon bag filter and posttreated at the temperature of 1000–1250◦C for 5 h under a reducing atmosphere (5% H2/N2 mixture gas) for crystallization and activation of divalent europium. To test the thermal degradation, the prepared CMS and commercial BAM samples were mixed with commercially available binder paste (Daejoo corporation) which is practically used for the formation of phosphor films in PDPs. Next, the phosphor paste, wherein the fraction of powder was 50 wt.%, was fired at 500 ◦C for 30 min in the air environment. The crystal phase of the prepared CMS particles and PL were then analyzed.X-ray storage phosphors

**22. Microwave synthesis** 

desired properties **[23].** 

**23. Spray pyrolysis** 

based on BaFBr:Eu are also made using this technique.

Fig. 27. Schematic diagram displaying the whole preparation steps of CaMgSi2O6:Eu blue phosphor particles by the spray pyrolysis **[24].** 
