粉红色釉料的研究

用陶瓷法、溶胶一凝胶法和共沉淀法以及三种矿化剂试验确定形成可用于透明釉和乳浊釉的粉红色料的最佳方法。

Rietveld refinement and optical properties of SrWO_4:Eu^(3+) powders prepared by the non-hydrolytic sol-gel method

We investigated the effect of annealing time on the structure and optical properties of Sr WO4：Eu^3＋ powders prepared by the non-hydrolytic sol-gel method and heat treated at 800 ℃ for 2,4,8 and 16 h.Thermogravimetric and differential thermal analyses revealed that Sr WO4：Eu^3＋ powders were obtained at about 800 ℃.X-ray diffraction patterns and Rietveld refinement data confirmed that all powders had a scheelite-type tetragonal structure.Micro-Raman and Fourier transform infrared spectra indicated structural order at short range and anti-symmetric stretching vibrations of O-W-O bonds associated with tetrahedral[WO4]clusters.Optical properties were investigated by ultraviolet-visible（UV-vis）diffuse reflectance,and photoluminescence（PL）data which provided the evolution of quantum efficiency（η）and lifetime（τ）.UV-vis spectroscopy evidenced intermediate energy levels within the band gap of Sr WO4：Eu^3＋ powders.PL properties validated that the Eu^3＋ electric-dipole（^5D0→^7F2）transition in PL emission spectra was dominant which proved that Eu^3＋ ions were positioned in a site without an inversion center.[（^5D0→^7F2）/（^5D0→^7F1）]band ratios showed that Eu^3＋ ions were located in a low symmetry environment.The PL emission,ηandτproved the dependence on the annealing time in the behavior of Sr WO4：Eu3＋powders with a higher relative emission PL intensity as well as higherηandτvalues related to other samples when heat treated at 800℃ for 8 h.

Red-emitting CaWO4:Eu^(3+),Tm^(3+)phosphor for solid-state lighting:Luminescent properties and morphology evolution

CaWO_(4):xEu^(3+),yTm^(3+)crystals were obtained by facile synthesis at low temperature by the microwaveassisted hydrothermal method(MAH).The phase formation,morphology,luminescent properties and ene rgy transfer were investigated.The X-ray diffraction(XRD)re sults show the formation of a scheelitelike tetragonal structure without the presence of secondary phases.The growth mechanism of hierarchical micro structures based on self-assembly and Ostwald-ripening processes was evaluated,obtaining different types of morphologies.The luminescence spectra of CaWO_(4):Eu^(3+),Tm^(3+)at 325 nm excitation show the predominance of red emission at the 5 D0→7 F2(Eu^(3+))transition at 624 nm.This feature signals dominant behavior of the electric dipole type.The presence of Tm^(3+)is notably evident in the absorption spectra by the related excitation transitions:3 H6→1 G4,3 H6→3 F3 and 3 H6→3 H4.Color parameters are discussed to characterize CaWO_(4):Eu^(3+),Tm^(3+)emission.The study of the emission spectrum as a function of the concentration of Eu^(3+)(x mol%)and Tm^(3+)(y mol%)indicates that the CaWO_(4):Eu^(3+),Tm^(3+)phosphors show stronger red emission intensity and exhibit the CIE value of x=0.63 and y=0.35.The photoluminescence results show 97%high color purity for CaWO_(4):4 mol%Eu^(3+),a high CRI(92%)and a low CCT of 1085 K.These results demonstrate that the CaWO_(4):Eu^(3+),Tm^(3+)red phosphors are promising as color converters for application in white light-emitting diodes and display devices.

Effect of different starting materials on the synthesis of Ba_(0.8)Ca_(0.2)TiO_(3)

Literature has reported the synthesis of barium calcium titanates by various synthesis methods such as solid state reaction,co-precipitation and polymer precursors.These compounds are usually obtained using calcium carbonate(CaCO_(3)),barium carbonate(BaCO3)and titanium oxide as starting materials.This study investigated the effect of different starting reagents on the synthesis of Ba_(0.8)Ca_(0.2)TiO_(3)(BCT)by complex polymerization method(CPM).Two sets of starting precursors were used:titanium citrate,CaCO_(3)and BaCO3,and titanium citrate and Ba1-xCaxCO3 solid solution precursor.Samples were crystallized at a temperature range from 400℃to 700℃for different time.The obtained powders were characterized by X-ray diffraction(XRD),thermogravimetry(TG)and differential thermal analysis(DTA),and Raman and infrared spectroscopy.The infrared spectroscopy indicated that the chelation processes of Ba,Ca,Ti and CA ions are very similar.The results showed that the use of CaCO_(3)and BaCO3 or Ba1-xCaxCO3 solid solution as precursors does not affect the final properties of BCT powders obtained by CPM.