Investigation of electrical properties of Zn substituted polycrystalline

Abstract

Polycryslalline CuCu-,Ti"Oll (CCTO) ceramic, and three ,erie.' of doped cera l.e. "Ca,.,Zn,Cu,Ti,OIl (CZeTO, x=o,o, 0.1, 0.2, 0,3. 0.4)", "Ca,.,La,Cu)Ti"4A1GO'O""' (CCTAO, x-(J O. 0, j. 0,2, (j 3, OAr and «Ca.:>,!La:"CuJTi,_,Al,O"_~;l (CLeTO, y=0.0, OJ)2, 0.04, 0.06 and 008)" were pr~parcJ by a conventionalsolid ,tate reaction technique, The poiycry,talline CeTO IS found to be .,ingle pha,e cubic perov,kite structure. It exhibits a maXImum dielectric constant 80800 and loss tangent 0,18 at lOOllz. Ba,ed upon a widely accepted ;ntcmnl-barrier-]aycr-~apacitancc model, the thelectric loss in the giant dielectric constant CeTO material i, expected to decrease a, the condudi, ity of the CC ro grain increases, The impedance spectroscopy analysis cvidenced thaI thi, idea wa, .,ueecssfully reali7"d for the cera ccramics ,intcred at differcnt temperatures, Thi.' mCan;; that, although the poiycry'talline CCTO has a huge dielectric comtant, it is not a good dielectric ma!elial for making capacitors due to its high dielectric loss. Thc ,arious Ca,_,Zn,CUjTi.;O" samp1Cs cxhibited annnproved dieleclric constanl compal'ed to the ul1dopcd cero, Among these. the Carl(,Zl1o,c,,] Ti40ll sample showed the highest dIelectric conSlant of E'- 165000 and also high los< tangcnt 2.78 at 100 Hz Howcvcr, lhe C~09Zl1<)ICu)Ti.;O" exhibits dielectric conslanl 36000 and a low dls.,ipation faclor O.lJ ~t 100 kHz at room tempCT"lure. The imped~nee 'pectroscopy analysis confim" that the decrease of dielectric loss i, mai nly due 10 the increase 01 wndlLctivity in the CZCTO grain. The La SUbSlillltion III various Ca,_,La,CuJTi),94Aloo,O'I07 also has been shown to I'edu~e lhe diclcctric loss remarkably while maintaining a high dielectric conSlant For Cao,L"o4Cu)TiJ"Aloo,;OII.97, lhe loss tang~'[]t was 0.12 al 100 kHz and the diclectric constanl wa, 7100 al same fre4uency, Jmpedan~e spectt'a indi~aled that due 10 r_aSUbSl1lutionthe conductivity of the CCTAO grain has lllcrea,ed for V"rious Cao sL""Cu) Ti4.yAlyO"_l"" it wa, observed that Al dopmg has reduced the dlC!eclric loss remarkably while mainmining a high dielectric constant. ror Ca"La,,,Cu) T1J'),Alo0.0 II 99, lhe loss tangent was 0,08 over thc fre4uency range of to'-l 0' Hz and thc dielectric constant was 8360 at i 0 kHz, Impedance 'pectra inciic"ted lhat due 10 Al doping the lesisti,ily of thc CCTAO gram boundary has increased by an order of magmtude ""d hence decreasc the dielectne l"s> in thcse ,"mples, These results ,how that the materials are helpful for practical apphcatiol1s.