Effect of oriented defect-dipoles on the ferroelectric and piezoelectric properties of CuO-doped (K 0.48 Na 0.52 ) 0.96 Li 0.04 Nb 0.805 Ta 0.075 Sb 0.12 O 3 ceramics

Abstract The orientation characteristics of the defect dipoles formed by acceptor ions ( Cu Nb ″ ′ ) and oxygen vacancies ( V O • • ) in CuO-doped (K 0.48 Na 0.52 ) 0.96 Li 0.04 Nb 0.805 Ta 0.075 Sb 0.12 O 3 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 T C . The poled ceramics with 1.0–3.0 mol% CuO displayed strong asymmetric P - E loops and a large internal bias field ( E i ), 3.89–4.57 kV/cm, when polarized at the temperature near T C . The enhanced piezoelectric coefficient d 33 , 186–192 pC/N, was obtained for the ceramics poled near T C when 0.02 ≤ x ≤ 0.03. The ceramics with oriented defect dipoles showed a relatively good thermal stability of d 33 until 180 °C.