Alkaline-earth metal silicates as well as many polyvalent metals silicates are prepared usually through aqueous solutions reactions between an alkaline silicate solution and the solutions of metal salts. The oxide composition of the designed glass is established by estimating of the molar ratios of precursors. The vitrification of the oxide compositions takes place directly by the reaction of the chemical precursors on the substrate. This paper presents an experimental study based on obtaining methods of nanocrystalline Zn(x)Cd(1-x)S from aqueous solutions. We have investigated the dependence of Zn(x)Cd(1-x)S nanoparticles size and properties on composition, pH and concentration of the starting solution. The method consists in co-precipitation of Zn(x)Cd(1-x)S from CdSO(4)/Cd(NO(3))(2) and ZnSO(4)/Zn(NO(3))(2) solutions, by adding an exceeding amount of Na(2)S at pH high values. The precipitation reaction takes place in aqueous solutions, in the presence of a chemical stabilizer as styrene-maleic anhydride or acrylic acid-maleic anhydride co-polymers. The stabilizer provides a colloidal state of the synthesized material and does not allow Zn(x)Cd(1-x)S nanoparticles to agglomerate. The nanocrystalline Zn(x)Cd(1-x)S electroluminescent pigments, the vitrification and the quality of the obtained thin films were studied by Optical Microscopy, Transmission Electron Microscopy and Scanning Electron Microscopy.

Undoped and neodymium doped quartz glasses were obtained by the hybrid sol-gel method. The vitrification was performed in He atmosphere. The Nd(3+) characteristic absorption bands in the UV and VIS were put into evidence. Investigations in the NIR range revealed a small amount (86 ppm) of OH(-) in the vitreous matrix. FTIR and Raman spectra exhibit the SiO(2) glass characteristic vibrations and also the characteristic vibrations of Si-OH and Si-Cl bonds. The photoluminescence peaks at 640, 920 and 1080 nm belonging to the Nd(3+) doped quartz glass were evidenced.

The aim of present paper was to find out the influence of structural inhomogenities upon the main parameter of optical ceramic obtained from zinc sulphide by hot pressing, IR transmission. It is directly influenced of microstructure characteristics of ceramic material. Microstructure of studied optical ceramic from zinc sulphide is influenced by starting powder parameters (purity, particle size distribution, stoechiometry) and processing conditions. Taking into account the experimental results we tried to relate transmission and microstructure, the last one being function of pressure, temperature, time, particle size distribution and purity.

In contrast with transitional metals whose spectra and color depends a lot of the ligands strength field, the sensitivity of the rare earth spectra is significantly weaker. This is the reason why the color of these ions is the same whatever the basic vitreous matrix. These properties permit to establish a relation for the determination of the concentration of these ions in vitreous matrix directly from the optical transmission spectra. The paper presents some samples of silica and phosphate glasses with lanthanides content for nonlinear optical applications synthesized at a laboratory scale. VIS-NIR transmission curves are presented, for several compositions. For the correlation of the lanthanides content with the specific optical absorption peak one used a method starting from the Lambert – Beer law. For the Nd2O3 concentration determination, it was used a method proposed by D.M. Dood and D.B. Fraser for the OH groups content, with an error of +4%. For specific peaks, expressions for lanthanides concentration in ppm, related to the optical transmission were found. A possibility appears to directly find the lanthanides concentration from the absorption coefficient at specific wavelengths for each vitreous matrix. The influence of matrix is discussed.

Alkaline earth metal silicates as well as many polyvalent metals silicates can be obtained through aqueous solutions reactions between an alkaline silicate solution and the solutions of metal salts. The vitrifiation of the oxide compositions, established by the necessary molar ratios for the projected glass, is realised by calculating the concentration of chemical precursors, through their reaction directly on the substrate. The sodium silicate viscosity in aqueous solution and the viscosity of nitrogenated compounds or oxalates necessary in the silicates synthesis is compatible with the necessary viscosity for ink-jet cartridges. The necessary silicates forming reactions were studied directly on the deposition support, so that the functional characteristics of the multicompartment ink-jet cartridges were used. Compositions were realised, in which the colouring effect was obtained with ionic colorants. The vitrifiation and the quality of the obtained thin films were studied through Optical Microscopy and Scanning Electron Microscopy.

The paper deals with optical and electronic properties of the aluminophosphate glasses containing Fe–Mn and Fe–Cr ion pairs in different concentration. The influence of the mixed alkali ions over the electronic properties has been investigated. The optical behavior (optical transmission) of the glass samples has been studied by UV-VIS spectroscopy and the refractive index dependency on wavelength has been discussed. The transmission spectra show features specific for the doping transition ions (TM), revealing different oxidation states of iron (Fe 2+ /Fe 3+ ), manganese (Mn 2+ /Mn 3+ ) and chromium (Cr 3+ /Cr 6+ ) in the vitreous network. Mössbauer spectroscopy offers information regarding the TM oxidation states, redox processes and the iron coordination symmetry in the vitreous network. In the case of Fe–Mn doped glasses, the percentage of Fe 2+ is about 40% and a doubled iron content leads to an increasing of Fe 2+ percentage up to 53%. The replacing of lithium ions by natrium ions (mixed alkali effect) provides an increasing of the Fe 2+ percentage up to 56%. The occurrence of the tetrahedral or octahedral symmetry of Fe 2+ ions bonded by O 2− ions depends on the transition ion nature and Li + /Na + ratio. Infrared absorption spectra of the pair transition ions-doped aluminophosphate glasses reveal optical phonons specific for the phosphate glass matrix.

Zinc and cadmium sulphide is a ternary compound used as a pigment, phosphors and semiconductor material. The paper presents an experimental study regarding the obtaining process of the nanocrystalline compound ZnxCd1-xS. In technical papers there are many recipes for colloidal ZnS and CdS synthesis in different working conditions and from various raw materials. Depending on the chosen recipe one can obtain colloidal ZnxCd1-xS particles of greater or smaller sizes. The pH and the concentration of the synthesis solution have a great influence on the dimensions and properties of synthesised particles. The method consists in co-precipitation of ZnxCd1-xS from CdSO4/ Cd(NO3)(2) and ZnSO4/ Zn(NO3)(2) solutions, by adding an exceeding amount of Na2S at high pH of the solution. The precipitation reaction takes place in the presence of a stabiliser, copolymer stiren-maleic anhydride. The stabilizer provides a colloidal state of the synthesized material and does not allow ZnxCd1-xS nanoparticles to agglomerate. This ternary compound has a high efficiency of the UV exciting energy conversion into visible light, applied in photo and electroluminescent cells.

The paper is an experimental study on obtaining method of nanocrystalline ZnxCd1-xS from aqueous solution. The inorganic ternary compound is used as a pigment, phosphors and semiconductor material. We have investigated the dependence of ZnxCd1-xS nanoparticles size and properties on composition, pH and concentration of the starting solution. The method consists in co-precipitation of ZnxCd1-xS from CdSO4/ Cd(NO3)(2) and ZnSO4/ Zn(NO3)(2) solutions, by adding an exceeding amount of Na2S at high pH of the solution. The precipitation reaction takes place in the presence of a chemical stabilizer as styrene-maleic anhydride or acrylic acid-maleic anhydride co-polymers. The stabilizer provides a colloidal state of the synthesized material and does not allow ZnxCd1-xS nanoparticles to agglomerate. This ternary compound has a high conversion efficiency of the excitation energy into visible light, applied in photo and electroluminescent cells.

The paper presents a wet synthesis method of doped zinc oxide by coprecipitation in order to obtain a semiconductor ceramic with nonlinear electric properties. The manufacturing of varistor with high electric performances involves the using of high purity materials synthesised by successive purification processes at 99.995% purity level. The solutions purification that contains Zn/sup 2+/ ions depends on type of starting zinc salts. The experiments were made with nitrate and sulphate solutions. After doping of these solutions for 0.5% Bi/sub 2/O/sub 3/-1% Sb/sub 2/O/sub 3/-0.5% MnO/sub 2/-0.5% Cr/sub 2/O/sub 3/-0.5% CoO composition, the simultaneous precipitation of all metallic ions was made. The hydroxides precipitation being different at same pH, the corrections for dopant quantities, on base of chemical analysis, were necessary. The resulted precipitates were analysed by DTA. The hydroxides precipitated from zinc sulphate solution show weight losses with 10% grater than hydroxides precipitated from zinc nitrate solution. The thermal decomposition of hydroxides from nitrate is faster and at approximately 400/spl deg/C was finished, comparatively with hydroxides from sulphates, at which this process is not over, up to 880/spl deg/C. The decomposition of hydroxides mixture precipitated from nitrates has an exothermic effect at 250/spl deg/C comparatively with hydroxides mixture from sulphate, which has endothermic effects only. These differences of thermal decomposition functions of synthesised hydroxides have major effects on oxide powders, from which will be formed ceramic for varistors. In this way, the oxide powders are finer than that obtained by normal way and can be sintered at low temperature. The ceramic microstructure realised from these oxides is very fine, the microcrystals grain size having 1-2 /spl mu/m, without porosity and with good chemical homogeneity.

Chemical synthesis by concomitant precipitation of metallic ions for obtaining a PLZT 10/65/35 composition starting from hydroxides and oxalates was made. Another task was the sintering of oxide powders obtained by thermal decomposition of synthesized precipitates using hot pressing method followed of heat treatment in oxygen stream.

These paper present the wet synthesis method of high purity cadmium and zinc sulphides for phosphors. As row materials are used zinc sulphide, cadmium sulphide and cadmium-zinc sulphide in order to obtain a large types of phosphors. These phosphors have incorporated in base structure well-defined quantities of dopants. Changes of dopants and thermal treatment must be obtained different wavelength of emitted radiation and different optic efficiency. Thus, ZnS hex:Cu emits at 561nm (green colour) with optical efficiency 90 % opposite to zinc silicate, ZnS cub:Cu,Ag emits at 528 nm (green colour) with optical efficiency 200 %, ZnS hex:Cu emits at 516 nm (green colour) with optical efficiency 100 %, ZnS cub:Zn emits at 470 nm (blue colour) with optical efficiency 190 %, ZnS cub:hg emits at 455 nm (dark-blue colour) with optical efficiency 220 %, (Zn,Cd)S:Ag emits at 565 nm (yellow colour), 556 nm (yellow-green colour), 550 nm (yellow colour), 540 nm (green colour), 537 nm (green colour) or 528 Nn (green colour) with optical efficiency 370 % opposite to zinc silicate, (ZnS, Cd):Cu emits at 530 nm and 528 nm (green colour) with optical efficiency 140 % opposite to zinc silicate.The utilised zinc sulphide must have a special purity. Was established that any impurities with greater concentration than 10(-6)-10(-5) % modify more or less the properties of product. Practically was established that materials utilised for above-mentioned purpose must have 99.99 - 99.999 % level purity. The control of reaction mechanism in order to achieve the best yield reaction in the same time with an advanced purification was experimented. Were achieved phosphors with 400 - 600 nm emission ranges. Also, influence of material parameters (particle size distribution, chemical homogeneity, structure) on luminescence emission parameters was studied.

The high purity powders synthesis and the hot-pressing technology, regarding optical ceramic materials, like MgF2, CaF2, ZnS, ZnSe was studied. The optimal conditions for the optical windows manufacture were established. It had been established the influences of the material purity and particle size distribution on the optical parameters.