Yunfei Chang

⟨001⟩ textured (K0.5Na0.5)(Nb0.97Sb0.03)O3 piezoelectric ceramics with high electromechanical coupling over a broad temperature range

⟨001⟩-oriented (K0.5Na0.5)(Nb0.97Sb0.03)O3 (KNNS) ceramics with a narrow orientation distribution (full width at half maximum=7.0°) were produced by templated grain growth using NaNbO3 templates. Excellent electromechanical properties were obtained from −70 °C to the polymorphic phase transition (PPT) at 160 °C. Textured KNNS ceramics show very high electromechanical coupling factors kp=0.64 and k31=0.37, high piezoelectric constants d33=208–218 pC/N and d31=−82 pC/N, and modest strain hysteresis (6.3%) at room temperature. These properties are superior to those of randomly oriented KNN-based ceramics with similar PPT temperatures.

Microstructure development and piezoelectric properties of highly textured CuO-doped KNN by templated grain growth

This paper demonstrates the production of 〈00l〉-oriented CuO-doped (K0.476Na0.524)NbO3 (KNN) piezoelectric ceramics with a polymorphic phase transition (PPT) temperature greater than 180 °C by templated grain growth (TGG) using high aspect ratio NaNbO3 template particles. A novel (to the KNN system) two-step sintering and annealing process combined with CuO doping is demonstrated to improve density and maximize texture quality (F00l = 99% and rocking curve FWHM = 6.9°) in textured KNN ceramics. The best electromechanical properties (kp ≈ 0.58, k31 ≈ 0.33, d33 ≈ 146 pC/N, To-t ≈ 183 °C, Tc ≈ 415 °C, er = 202, and tan δ = 0.016) are achieved in 1 mol% CuO-doped KNN with F00l = 99% and a relative density of 96.3%. The values of d33, kp, and k31 are 70–90% higher than randomly oriented ceramics and are obtained without a significant reduction in the PPT temperature, resulting in stable piezoelectric performance over a wide temperature range (−50 to 180 °C). These results show that high-quality textured KNN can be obtained by TGG and that a reactive matrix is unnecessary.

Enhanced texture evolution and piezoelectric properties in CuO-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 grain-oriented ceramics

In this work, both crystallographic texture and doping engineering strategies were integrated to develop relaxor-PbTiO3 (PT) based ternary ferroelectric ceramics with enhanced texture evolution and superior electromechanical properties. CuO-doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (PIN-PMN-PT) piezoelectric ceramics with [001]c texture fraction ≥97% were synthesized by templated grain growth. The addition of CuO significantly promotes densification and oriented grain growth in the templated ceramics, leading to full texture development at dramatically reduced times and temperatures. Moreover, the CuO dopant remarkably enhances the piezoelectric properties of the textured ceramics while maintaining high phase transition temperatures and large coercive fields. Doping 0.125 wt. % CuO yields the electromechanical properties of d33 = 927 pC/N, d33* = 1510 pm/V, g33 = 43.2 × 10−3 Vm/N, Kp = 0.87, Ec=8.8 kV/cm, and tan δ = 1.3%, which are the best values reported so far in PIN-PMN-PT based ceramics. The hi...