A　CoCO3　added　Pb((Zn1/3Nb2/3)(0.20)(Zr0.30Ti0.50)(0.80))O-3　(0.2PZN-0.8PZT　+　xCoCO(3))　system　has　been　prepared　and　investigated.　The　tetragonal　distortion　c/a　of　specimens　increases　abruptly　with　increasing　CoCO3　content,　but　is　almost　constant　for　x　＞=　0.2　wt%,　confirming　that　the　solubility　limit　of　CoCO3　in　0.2PZN-0.8PZT　is　about　x　=　0.2　wt%.　Complex　impedance　spectroscopic　analysis,　in　the　temperature　range　of　250-300　degrees　C　from　1　mHz　to　10　MHz,　provides　another　evidence　that　0.2　wt%　is　indeed　the　solubility　limit.　Both　spectroscopic　peaks　of　Z　＇＇　and　M　＇＇　vs　frequency　are　observed　in　the　similar　frequency　region,　indicating　the　approximated-Debye　behavior　in　the　studied　systems.　Temperature　dependent　bulk　relaxation　values　are　found　to　obey　linear-Arrhenius　fit.　Based　on　the　activation　energy　values,　it　can　be　concluded　that　in　CoCO3　doping　0.2PZN-0.8PZT,　both　the　single　and　double　ionized　oxygen-vacancies　contribute　to　the　conduction　process.　(C)　2012　Elsevier　B.V.　All　rights　reserved.