Crystal LaOCl

Single-crystal LaBg in well-formed parallelipipeds (0.15 X 0.15 X 2 m) grows when LaBrj is used as transport agent in an Ar atmosphere with T in the source and crystallization zones of 1150 and 900°C, respectively. The transport probably proceeds through the subhalide. The amount of transported LaB is increased by a factor of 10 when oxygen is replacing Ar, and LaClj is substituted for LaBrj. The more efficient transport in this case is due to the formation of LaOCl. 

Within the estimated uncertainties, table 7 shows that a common set of intrinsic parameters for k = 6 can be found which describes all samples studied there. One remarkable difference is observed only in the case of B (Rq ) for LaOCl Pr3+. However, this difference was caused simply by the use of different data sets in the determination of the crystal-field parameters. 

The excitation mechanism of the anti-Stokes emission is as follows. First the ion is excited into the Dq level. Although the Fo- Do transition is highly forbidden (J = 0- J = 0), it has a rather high absorption strength in LaOCl due to the strong linear crystal-field component at the La CEu ) site. The lifetime of the Do level is long (of the order of milliseconds). A second photon is now absorbed, which raises the system to the charge-transfer state. This is an allowed transition. More-... 

The halogenides and nitrates of the rare earth elements and yttrium are very soluble in water. Various hydrates may be obtained by evaporation of the solutions until they crystallize when cooled. The nitrates are decomposed to the oxides by ignition, but the hydrated chlorides melt and hydrolyze when ignited and basic chlorides such as LaOCl are formed. The very useful anhydrous chlorides are prepared by the careful heating of hydrated chlorides with excess ammonium chloride. ... 

Membranes of LaOCl can be manufactured from aqueous solutions of lanthanum chloride. After an adequate sintering step, LaOCl crystallizes at 400°C and is very stable up to 800°C, giving pore sizes as small as 1.5 nm [24], These membranes are used as catalytic reactors. 

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