NM, ANDERS~'U, K. CLAtlS~I M.T. Hu'rcm~Gs an~ W.G, ffI'IRLING " fuel cells, i. oxygen ~.~o~ and as a high t~pera-At room t~mperatn~ pu~ zi~onla (ZIO2) has a ~ ~ami~ Its use as an artificialgem stone hasled m~ocilnic crystal stn*ture. On heating it traa~ to the ready availabilily of large s~ngle crystals [l]. fo~ firstly to a tetragonal pha~ at ~ 1273 K ~d The eler i~l neut rallt y of YSZ is maintained by finaUy to a fluotlt e mbiz struct u~ which is stable be-~cancies in the oxyg~ sublat ti~, and t his defccfive t~n 2643 K and the melting temperature of 2988 stmctu~ gi~ rise to its ~ygen ion conductivity. IC The high temperature fluorite plm~ of ZrO2 ~n Diffraction studie~ of stabilized zirconla ruing ele~ bes~abilizedat ambient tempe~turebytheaddition trons [2,3], X-~ys [4] and neutrons [5] have e~ of various ~bic oxides having di-val~t (CaO, M40, t ablished the ~ tlm~a~raged structure of the etc.) or trl-valent (Y20~, LabOr, etc.) cations in a unit r andshowthat~laxation~amund~r wide rouge of ~noentrations. yttria.stabifized zir-vacancy, H~r "Mtb such high v~ncy concen-~nia (YSZ) finds many div~ technologist al~ tmtions st~ng ~eiztions betwe~ the va~ci~ ~r, ~d the~ have b~ p~bcd by diffuse ele~ "v~t a~ X~h~i~ L~., 7112 Tavis~k ~, ~a-t~ [ ~,31, X-my [ 4] and neutron 16-8 ] s~ttetlng, don' WCIH 9LT' gI~ In this paper ~ ~port the ext~sion of ~me of the 9 pre~t address: Rut~rd Appleton ~mt~, CMItua, OXll ~X, tSK. ~rlizr diffu~ neut~n ~ttering mcasu~ments to --Print ~dr~ ~ ~t of ~y,i~ Umve~ of Km~, elevated temperatures in o~der to gain furth~ in for. Keet e, Stuffs,, ST5 5BG, UK. ration on the dynmle bebaviouy of the defects, and