Preparation and Characterization of Orthophosphates for Optics and Electronics

The present work concerns sustainable development of environmentally compatible electronic materials. Our investigations have mainly focused on nonlinear orthophosphate compounds and more particularly on eulytite phases. Phosphate eulytites crystallize with the non centrosymmetric space group 1-43d which is compatible piezoelectronic and nonlinear optical properties. Indeed, second harmonic generation （SHG） tests performed on systems of the type BIIaMm（PO4）3 （with Bn= Cd, St, Ba, Pb; MIII= Ln, Bi） showed better performance than KDP （about 100 KH2PO4）1）＇2）. The practical interest of eulytite compounds has been evidenced by various authors in various domain of modem technology; i） medicine （positron tomography）, ii） nuclear industry （fuel rods control）, iii） high energy physics （CERN detector）, iv） etc. Indeed CERN in Geneva is currently using 1300 liters of Bi4（GeO4）3 single crystals. Then, bismuth silicates and bismuth germinate Bi4（SiO4）3 and Bi4（GeO4）3 have important applications in high energy physics as for example, scintillators （ionizing radiation detectors, etc.）. The main aim of our research work is to try to correlate between the chemical composition, the crystalline structure and the physical properties （optical, piezoelectric, etc.） of the phosphate eulytites free of toxic elements with various dopants （Ce3＋, Eu3＋, etc.）. As single crystals are of high cost and difficult to grow, glasses have low technological efficiency of our planed optical applications. Therefore, we are trying to prepare transparent ceramics which are expected to give rather excellent satisfaction. We prepared BaaBi（PO4）3 eulytite phases by two difference methods. One is based on the use of CO2 gas blowing in order to dissolve starting materials （like Baa（PO4）2） and crystallize pure eulytites. The second process is using the sol-gel method.

Preparation of titanium phosphate white pigments with titanium sulfate and their powder properties

Titanium oxide that has photocatalytic activity is used as white pigment for cosmetics.A certain degree of sebum on the skin is decomposed by the ultraviolet radiation in sunlight.In this work,as novel white pigment,titanium phosphates were synthesized with titanium sulfate and phosphoric acid for cosmetics.Their chemical composition,powder properties,photocatalytic activity,color phase,moisture retention,and smoothness were studied.These titanium phosphates had less photocatalytic activity to protect the sebum on the skin.Samples without heating and those heated at 100℃showed high reflectance in the range of visible light.Sample prepared in Ti/P=3/2 had higher moisture retention than samples prepared in other Ti/P ratios.

Microstructure,hardening and deuterium retention in CVD tungsten irradiated with neutrons at temperatures of defect recovery stagesⅡandⅢ

Samples of ultra-high-purity tungsten prepared using chemical vapour deposition(CVD)technique were irradiated with neutrons at temperatures T_(irr)=373-483 K(stage Ⅱ of defect recovery)and T_(irr)=573-673 K(stage Ⅲ)up to 0.15 displacements per atom(dpa)in the Belgian reactor(BR2).The study of the microstructure of neutron-damaged samples using transmission electron microscopy(TEM)revealed visible defects with a predominance of dislocation loops.With an increase in the neutron irradiation temperature,the spatial distribution of the loops acquired pronounced inhomogeneity,and their average size moderately increased.Cavities and voids were not observed.Irradiation-induced hardening was found and a linear correlation was obtained between Vickers microhardness and nanohardness for undamaged and neutron-irradiated CVD-W samples.Irradiation of tungsten with neutrons led to a significant increase in the retention of deuterium,which accumulated mainly in vacancy-type traps.Furthermore,the influence of the columnar grain structure in low-dose neutron-irradiated tungsten seemed to be non-trivial upon deuterium retention.