http://cgcri.csircentral.net/911/3/SPS-J_Alloys_Compd.pdf

EPR, FTIR, optical absorption and photoluminescence studies of Fe2O3 and CeO2 doped ZnO–Bi2O3–B2O3 glasses

Cerium oxide is commonly added to silicate glasses as an optical property modifier In particular, UV absorption, decoloration via redox coupling, and resistance to radiation-induced darkening are influenced by the addition of this rare-earth oxide However, the limited solubility and visible color of rare-earth oxides in silicate glasses prevent any further beneficial enhancement of properties which might result from increasing the CeO2 content In contrast, rare-earth oxides are extremely soluble in phosphate glasses; for example, a binary cerium phosphate glass can incorporate up to 40 mol% CeO2 Moreover, since the UV absorption edge of the phosphate network is blue-shifted compared to the silicate network, the effect of the Ce3+ absorption band tail on yellow coloration can be minimized In this study, glasses in the cerium aluminosilicophosphate system were synthesized and a variety of physical and optical properties were measured including: density, refractive index, glass transition temperature, hardness, fracture toughness, and the location of the UV absorption edge At ∼9 mol% CeO2, these cerium aluminosilicophosphate glasses exhibit similar coloration to commercially available silicate glasses which contain ∼04 mol% CeO2 Semi-quantitative photoemission analysis of the Ce oxidation states showed insignificant differences in the Ce3+/Ce4+ ratio between the phosphate and silicate glass systems

Synthesis and properties of cerium aluminosilicophosphate glasses

A new inorganic pigment based on rare earth phosphate has been synthesized with the goal of preparing ecologically and environmentally friendly specific pigments. A yellow–green pigment that consists of nontoxic elements was obtained by doping calcium ions into the cerium orthophosphate lattice. Characterizations using XRD, UV–vis spectroscopy, and colorimetric assessment revealed that the formation of a Ca-doped CePO4 solid solution was responsible for the appearance of the color.

Synthesis of an Environmentally Friendly and Nontoxic New Pigment Based on Rare Earth Phosphate

Nanocrystalline rod shaped calcium doped cerium phosphate yellow-green pigment particles having an average length of ~100 nm and aspect ratio 10 even after calcination at 600 °C have been realized through an aqueous sol–gel process. The morphology, particle size and identification of the phase are determined by using different analytical tools such as transmission electron microscopy (TEM), photon correlation spectroscopy (PCS), Fourier-transform IR (FTIR) and X-ray diffraction (XRD). Brunauer–Emmett–Teller (BET) nitrogen adsorption analysis showed the pigment particles are mesoporous texture having specific surface area 42 m2 g−1 and average pore size 153 A. Thermogravimetric (TG) analysis is used to explain the thermal phase stability of the pigment. UV–Visible spectroscopy and colorimetric analysis are also done. The typical yellow-green color has been obtained even after heating to as low as 600 °C, which is 300 °C lesser than reported. Systematic study on synthesis and effect of temperature on color are presented.

Environmentally benign sol–gel derived nanocrystalline rod shaped calcium doped cerium phosphate yellow-green pigment

Green and selective toluene oxidation–Knoevenagel-condensation domino reaction over Ce- and Bi-based CeBi mixed oxide mixtures

In a number of ionic crystals an absorption peak or peaks just beyond the sharp absorption edge and due to excitons is frequently observed. The shape of the curve of exciton absorption has been well accounted for by Toyozawa [1]. Mort and Davis [2] have discussed the possibility of the existence of excitons in glassy materials. Originally it was suggested that exciton states should exist but that their lifetime would be so short that it would be virtually impossible to detect them. More recently it seems that glassy SiO2 is rather different in its electronic structure from other oxide glasses whose optical properties have been studied. The electron drift mobility is much higher than the normal values characteristic of a hopping process and suggests that the mobility edge in SiO2 is very near the band edge, so that the behaviour of electrons is more nearly similar to that in a crystalline semiconductor. There is evidence of exciton absorption in SiO2 and this has been discussed in detail by Mott [3]. This process is substantially modified by the incorporation of sodium monoxide in the silica as

Ravishankar Harani

Papers

Excitonic absorption in cerium phosphate glasses