SrO Powders Research Articles

Radiation damage in oxides. II. Defect formation in CaO and SrO

For pt.I see abstr. A36337 of 1973. The formation of cation and anion vacancies has been studied in high purity CaO and SrO powders after irradiation by 20 MeV protons. The rate of formation of cation vacancies fits a model of interstitial-vacancy recombination. Isochronal annealing curves show that the isolated vacancy concentration is enhanced by thermal treatment at temperatures just below those at which the isolated vacancy begins to disappear. This is interpreted in terms of the decomposition of a vacancy-vacancy or vacancy-impurity aggregate. At slightly higher temperatures (640K for CaO) the isolated vacancy is converted to the vacancy-hydroxyl ion complex and isothermal data indicates close to 100% conversion. At higher temperatures the vacancy-hydroxyl ion complex is destroyed. The probable mechanism of the first process is vacancy diffusion with an activation energy of 1.8 eV, to a hydroxyl ion where the vacancy is trapped and partial charge compensation occurs. At higher temperatures it seems likely that diffusion of interstitial cations to the vacancy occurs with an activation energy of 3.1 eV. The efficiency of vacancy production is an order of magnitude less than that predicted for primary displacements confirming the importance of recombination between vacancies and those interstitials formed within a critical volume around the vacancy.

Phase study on solid fission products, Ba, Sr and Zr in oxide fuel

Behavior of pseudo-fission products (Ba, Sr, and Zr) as oxides in UO 2 has been investigated by means of high-temperature X-ray diffraction and microprobe analysis. Two identifiable compounds were formed as reaction products in the mixed oxides which initially consisted of UO 2 , BaO, SrO, and ZrO 2 powder. These compounds were present and were identified crystallographically as (Ba, Sr) ZrO 3 and (Ba, Sr)UO 3 after heat treatment of the powders at 1500°C for 30 min. Both compounds are isostructural with perovskite, CaTiO 3 , and the lattice parameters of both (Ba, Sr)ZrO 3 and (Ba, Sr)UO 3 decrease with increasing content of Sr. (Ba, Sr)UO 3 is decomposed almost completely at 1800°C while (Ba, Sr) ZrO 3 is stable up to 2000°C. The behavior of Ba, Sr, and Zr in fuel under irradiation is discussed. Le comportement des produits de pseudo-fission (Ba, Sr et Zr) comme oxydes dans UO 2 a été étudié par diffraction aux rayons X à haute température et par analyse à la microsonde. Deux composés identifiables se forment comme produits de réaction dans les oxydes mixtes qui étaient constitués initialement par une poudre de UO 2 , BaO, SrO et ZrO 2 . Ces composes étaient présents et furent identifiés du point de vue cristallographique comme étant (Ba, Sr)ZrO 3 et (Ba,Sr)UO 3 après traitement thermique des poudres à 1500°C pendant 30 min. Ces deux composés sont isomorphes de la perovskite CaTiO 3 et les paramètres réticulaires à la fois de (Ba, Sr)ZrO 3 et (Ba,Sr)UO 3 diminuent avec la teneur croissante en Sr. (Ba,Sr)UO 3 est décomposé presque entièrement a 1800°C tandis que (Ba,Sr)ZrO 3 est stable jusqu'à 2000°C. Le comportement de Ba, Sr et Zr dans le combustible sous irradiation est discuté. Das Verhalten der Spaltproduktoxide des Bariums, Strontiums und Zirkons in UO 2 wurde durch Simulationsversuche röntgenographisch bei hohen Temperaturen und mit der Mikrosonde untersucht. Im Oxidgemisch, das ursprünglich aus UO 2 , BaO, SrO und ZrO 2 bestand, werden als Reaktionsprodukte zwei Verbindungen gebildet, die nach einer halbstündigen Wärmebehandlung der Pulver bei 1500°C kristallographisch als (Ba, Sr)ZrO 3 und (Ba,Sr)UO 3 indentiflziert wurden. Beide Verbindungen sind dem Perovskit CaTiO 3 isotyp, die Gitterkonstante des (Ba,Sr)ZrO 3 und (Ba,Sr)UO 3 nimmt mit zunehmendem Strontium-Gehalt ab. (Ba,Sr)UO 3 zerfällt fast vollständig bei 1800°C, während (Ba,Sr)ZrO 3 bis 2000°C stabil ist. Das Verhalten von Barium, Strontium und Zirkon im Brennstoff unter Bestrahlung wird diskutiert.

Far-infrared surface-activated band-mode absorption in strontium oxyde crystalline powder

Far-infrared transmission measurements of crystalline SrO powder sample at 300°K and 100°K have been performed. The free boundary of individual grain activates one-phonon band-mode absorption and yields information about phonon frequencies at critical points of the perfect crystal. Measured values are correlated with dispersion curves obtained by J.P. Mon using breathing-shell model. Discussion of Rosenstock-Hass approach is done.