This study offers a new method to synthesize facilely willemite (Zn2SiO4) based phosphor at the temperature of 800 °C. The ZnO-SiO2 nanocomposite was calcined at different temperatures between 500 and 1000 °C. The structural, morphological and optical properties of the nanocomposite obtained at various calcination temperatures were studied using different techniques. The FT-IR, XRD and the UV-vis result confirmed the formation of willemite phase. The precursor was confirmed to be amorphous by XRD at room temperature, but upon calcination temperature at 500 °C, it was transformed into a crystalline structure. The crystallinity and the particle size of the nanocomposite increase as the calcination temperature were increased as revealed by XRD and TEM measurement. The sample exhibits a spherical morphology from 500 to 800 °C and dumbbell-like morphology above 800 °C as shown by the FESEM images. The absorption spectrum suffers intense in lower temperature and tends to shift to lower wavelength in the UV region as the calcination temperature increases. The band gap values were found to be increasing from 3.228-5.550 eV obtained between 500 to 1000 °C, and all the results confirm the formation of willemite phase at 800 °C.

Worldwide commercial interest in the production of cerium doped yttrium aluminium garnet (YAG:Ce) phosphors is reflected in the widespread use of white light emitting devices. Despite of the fact that YAG:Ce is considered a “cool phosphor” it is the most important in white LED technology. This article reviews the developed techniques for producing phosphors with superior photoluminescence efficiency, including solid-state reaction, sol-gel and (co)precipitation methods. Also, by co-doping with rare earth elements, a red/blue shift is reached in the spectrum. The characteristics of YAG:Ce phosphors are investigated because the properties of the phosphors are strongly influenced by the synthesis routes and the sintering temperature treatment. After the phase analysis, morphology and emission studies of the phosphors there may be seen the conditions when the transition from the amorphous phase to the crystalline phase appears, when luminescent properties are influenced by the crystalline form, purity, average size of the particles, co-doping and so on.

In zinc electrowinning, small amounts of manganese ions additives are needed in the electrolyte to reduce the corrosion of anodes and minimize the contamination of cathodic zinc by dissolved lead. However, excess manganese oxide could cover the dimensionally stable anodes (DSA) surface and decrease their service life. Additives of phosphoric acid are put in the electrolyte to complex the manganic Mn3+ ion and hence reduce its disproportionation to MnO2. In the investigation, phosphoric acid was added to sulfuric acid or zinc electrolytes, and conventional and recent electrochemical measurements were carried out to examine electrochemical behaviour of DSA (Ti/IrO2-Ta2O5) anode during zinc electrolysis at 48 mA/cm2 and 39°C. It was observed that the anodic potentials of DSA anodes were lower by 27 mV after 5 h polarization in the zinc electrolyte containing 35 g/L phosphoric acid at 39°C. Electrochemical impedance measurements show that the addition of 35 ml/L H3PO4 to the zinc electrolyte can increase impedance resistances of the DSA mesh anodes. Cyclic voltammogram studies (CV) at a scan rate of 5 mV/s without agitation show that the oxidation peak in the solution with 35 ml/L phosphoric acid addition is highest, followed by that with 17 ml/L phosphoric acid addition and that without addition of phosphoric acid.