Synthesis and Luminescence Studies of Eu doped AlSrLaO 4 Phosphor
AlSrLaO4 phosphors were synthesized using standard solid state reaction [SSR] method with varying Eu molar concentration as 0.1, 0.2, 0.3, 0.4, 0.7, 1.0, 1.5, 2.0 and 2.5%. The mixture of reagents was ground together to obtain a homogeneous powder in acetone base. To prepare Aluminum Strontium Lanthanate (ASL) doped with various concentrations of Eu, consists of heating stoichiometric amounts of reactants at 1000°C for 2 h in a muffle furnace. The received powder being ground thoroughly using an agate mortar, to ensure the best homogeneity and reactivity, powder was transferred to alumina crucible, and then reheated in a muffle furnace at 1200°C for 4 hours. The phosphor materials were cooled to room temperature naturally. All samples were found out to be white who are studied for photoluminescence [PL]. Photoluminescence spectra were recorded at room temperature using Shimadzu-5301 Spectrofluorophotometer. The phosphors are characterized using XRD and SEM. The effect of doping of Eu in ASL on the PL emission/excitation was also studied. Eu shows all its primary allowed emissions hence it is concluded that this phosphor can be used in display devices.
Inorganic Phosphors: Compositions, Preparation and Optical Properties
Inorganic Phosphors: Compositions, Preparation and Optical Properties addresses practical and theoretical aspects of inorganic phosphors used in lighting and display applications. Authors Yen and Weber present the synthesis of phosphors in a ...cookbook... style that features nearly 300 ...recipes... using the most up-to-date guidelines and methods. They also categorize nearly 500 phosphors in terms of chemical composition and luminescence output wavelengths, summarizing their physical and emissive optical properties. This book is the first of its kind to provide a combined practical and technical foundation that can be used in commercial and academic research and development of new phosphors and applications.
Hygroscopic Expansion of some Casting Investments
CREDIT is generally given to Taggart1 for introducing the cast gold inlay to the dental profession. Although he realized that gold shrinks when cooled from molten state to solid state of room temperature, the investment available to him did not supply sufficient compensation. In 1910, Van Horn2 published a paper dealing with a method by which he obtained the compensation by means of wax expansion. The next major research in connection with this problem was the work of Coleman3 at the National Bureau of Standards. He determined the gold shrinkage to be 1.25 per cent and presented a casting technic with compensation values of quantitative nature. The total compensation for the gold shrinkage was obtained by the combination of the setting and thermal expansion of the mold. This procedure is the general practice followed at the present time for compensation. There are some disadvantages to this method. Skinner has indicated the difficulty of obtaining smooth castings and the improper compensation for the casting shrinkage.4 It has been found by Hollenback5 and Scheu6a that castings made at a high temperature are rougher than those made at a low temperature (450° C.), depending upon the great difference in thermal expansion between plaster of Paris and silica, which causes a poor union of the fine particles. This may also result in friability and there may be some warpage due to the differential expansion. A method which provides sufficient compensation at a low mold temperature is the hygroscopic casting technic.b Wilson7 showed that certain plasters expand as much as 0.0044 inch to the inch by taking up moisture from the air. With this information at hand, Scheula, b tested some commercial investment to determine what results the addition of moisture would have. He found6b: (1) All of the casting investments that were tested expanded. (2) The thicker the mix, the greater the expansion. (3) A mix with hot water expanded more than one with cold water. (4) The time at which the mix is placed in the water is of great importance. It was found that if the mix is placed in the water early, it would not expand so much as when placed in a little later. It was also found that if the mix was placed in the water after a certain time, it could not expand to the maximal amount. (5) The temperature of the water in which the mix is placed is important, for two reasons; (a) the temperature of the water controls slightly the expansion of the investment, and (b) water at a temperature of 1000 F. slightly softens the wax pattern so that the fine margins are not marred while expansion is taking place. The mix should remain in the water at least 20 minutes to obtain the full expansion, after which time no further expansion is obtained.