Enhanced piezoelectric properties of Fe2O3 and Li2CO3 co-doped Pb[(Zr0.48Ti0.52)0.8(Zn1/3Nb2/3)0.125(Mn1/3Nb2/3)0.075]O3 ceramics for ultrasound transducer applications

Pb [(Zr0.48Ti0.52)0.8(Zn1/3Nb2/3)0.125(Mn1/3Nb2/3)0.075]O3 + 0.07 wt.% Li2CO3 + x wt.% Fe2O3 ceramics (PZT–PZN–PMnN; x = 0–0.35) were prepared following the B-site oxide mixing method. Results obtained using the Rietveld refinement and Raman spectroscopy techniques revealed that all ceramic samples possessed a single perovskite phase and exhibited the coexistence of rhombohedral (domains of 71° and 109°) and tetragonal phases (domains of 90° and 180°) (R3c-P4 mm). The widths of these domains ranged between 60 and 120 nm. However, the tetragonality c/a ratio tended to increase with an increase in the Fe2O3 content. The resultant 0.25 wt.% Fe2O3 and 0.07 wt.% Li2CO3 co-doped PZT–PZN–PMnN ceramic exhibited good dielectric and piezoelectric properties (density (ρ) = 7.86 g/cm3). The materials were also characterized by good dielectric constant (εr) = 1408, coupling coefficient in the planar mode (kp) = 0.64, piezoelectric constant (d33) = 455 pC/N, and excellent mechanical properties (mechanical quality factor (Qm) = 1455, dielectric loss (tanδ) = 0.003). The sample properties were analyzed at the low sintering temperature (TS) of 1000 °C. Further, a Langevin transducer was fabricated under conditions of the optimal ceramic composition. The Langevin transducer was characterized by a resonant frequency (fr) of 46.8 kHz and an anti-resonance frequency (fa) of 48.5 kHz. The coupling coefficient was 0.26, and the corresponding impedance values were 45.5 Ω (at fr) and 11,663 Ω (at fa), respectively.