PRODUCTION AND THERMAL ANNEALING OF LATTICE DEFECTS IN KCl

Some investigations were performed to obtain more information about the production of defects in alkali halides during X-irradiation. Combined measurements of tIie macroscopic volume change and the change of the Iattice parameter of KC1 were performed. Color centers in additively colored KC1 are formed from Schottky-defect vacancies, whereas in X-irradiated KC1 they are formed from vacancies which are parts of Frenkel defects. Further, the production of vacancies, i. c. a plus F centers by X-rays in KCI of different origins, dislocation densities and of different divalent impurities is studied at liquid helium temperature. It is concluded that the generation of vacancies at liquid helium temperature is an intrinsic process. The annealing behaviour of a, Fand Hcenters and the annealing of an absorption band at 195 nm shows, that during X-irradiation at liquid hclium temperature vacancies and interstitials are formed in KC1 which recombine in distinct annealing stages. An analysis of the annealing curves gives the activation energy and the order of reaction. It is concluded from combined irradiation and annealing experiments at liquid helium and at liquid nitrogen temperature that the same pri~nary process should be valid for the defect formation at liquid helium and at liquid nitrogen temperature. Introduction. Though KC1 with color centers about the type of disorder, which color centers reprehas been investigated many times, little is known sent in thc crystal Iattice, can be obtained from combiabout the mechanis~n by which they are formed ned measurements of the macroscopic volume change during irradiation [l]. There are some indications and the change of lattice parameter. B centers were that during irradiation of alkali halides color centers introduced by additive coloration and X-irradiation are formed as Frenkel defects (see e, g. [2]). Investigaat room temperature. Lattice paratneter change was tions of the growth of the color center absorption obtained from the shift of the (800) Cu Kx X-ray bands especially F band 131 show that a t liquid helium diffration peaks. The volume change was studied by temperature the creation of F centers should be an measuring the mass-density change using a hydrostatic intrinsic process. The purpose of this paper is to flotation method. report about some recent investigations performed The results are given in figure l. Curve A shows to get more informations about the production of the results Tor additively colored KC1 and curve X defects in alkali halides during X-irradiation. shows the results for two different samples of KC1 after subsequent X-irradiation. The dashed lines I . Volume and lattice parameter change in X-irxaindicate the expected results for different kinds of diated and additivcly colored KCI. Informations disorder. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1967428 C 4 164 A. BEHR, H. PBISL AND W. WAXDELICH FIG. 1 . Rclaiivc lattice parameter change An/n and relative mass-density change 113 A p / p in ndditively wlored (curve A) and X-irradiated (curve X) KCI. If only Schattky defects are created, the relative rnacroscopic density change is mainly caused by the creation of additional lattice sites and onIy partly because of latticc pararnclcr change. The concentration of additional created latticc sites which is equal to the concentration of vacant lattice sites c, can bc obtained from the dcnsity and lattice parameter data : c, = Aplp 3 Anla . For pure FrenkcI disorder