Effect of oriented defect-dipoles on the ferroelectric and piezoelectric properties of CuO-doped (K0.48Na0.52)0.96Li0.04Nb0.805Ta0.075Sb0.12O3 ceramics

The orientation characteristics of the defect dipoles formed by acceptor ions (CuNb″′) and oxygen vacancies (VO
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- ) in CuO-doped (K0.48Na0.52)0.96Li0.04Nb0.805Ta0.075Sb0.12O3 piezoceramics were investigated. The ferroelectric and piezoelectric properties of the ceramics were obviously affected by the defect dipoles which are oriented along with the domains when poled under a dc electrical field of 3.5 kV/mm at the temperature near TC. The poled ceramics with 1.0-3.0 mol% CuO displayed strong asymmetric P-E loops and a large internal bias field (Ei), 3.89-4.57 kV/cm, when polarized at the temperature near TC. The enhanced piezoelectric coefficient d33, 186-192 pC/N, was obtained for the ceramics poled near TC when 0.02 ≤ x ≤ 0.03. The ceramics with oriented defect dipoles showed a relatively good thermal stability of d33 until 180 °C.