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.