Abstract
In this work, the process of two-stage modifications for (Ba0.97Ca0.03)(Ti0.96Sn0.04-xHfx)O3 (BCTS4-100xH100x) ceramics was studied. The trade-off composition was obtained by Hf substitution for Sn and MnO2 doping (two-stage modification) which improves the temperature stability and piezoelectric properties. The phase structure ratio, microstructure, and dielectric, piezoelectric, ferroelectric, and temperature stability properties were systematically investigated. Results showed that BCTS4-100xH100x piezoelectric ceramics with x=0.035 had a relatively high Curie temperature (TC) of about 112 °C, a piezoelectric charge constant (d33) of 313 pC/N, an electromechanical coupling factor (kp) of 0.49, a mechanical quality factor (Qm) of 122, and a remnant polarization (Pr) of 19μC/cm2. In addition, the temperature stability of the resonant frequency (fr), kp, and aging d33 could be tuned via Hf content. Good piezoelectric temperature stability (up to 110 °C) was found with x =0.035. BCTS0.5H3.5 + a mol% Mn (BCTSH + a Mn) piezoelectric ceramics with a = 2 had a high TC of about 123 °C, kp ∼ 0.39, d33 ∼ 230 pC/N, Qm ∼ 341, and high temperature stability due to the produced oxygen vacancies. This mechanism can be depicted using the complex impedance analysis associated with a valence compensation model on electric properties. Two-stage modification for lead-free (Ba0.97Ca0.03)(Ti0.96Sn0.04)O3 ceramics suitably adjusts the compositions for applications in piezoelectric motors and actuators.
Highlights
Lead zirconate titanate, PbZrO3, (PZT)-based piezoelectric ceramics have superior electrical and piezoelectric properties, high Curie temperature, and relatively good temperature stability
Compared with polymorphic phase transition (PPT), morphotropic phase boundary (MPB) would be a disadvantage at the Sn- and Zr-rich boundaries of BCTS or BCTZ ceramics, respectively, which would reduce TC
Probably reduce the stability of the planar electro-mechanical coupling factor and piezoelectric properties with increasing temperature. This is not beneficial for lead-free piezoelectric ceramics applied in electrical devices at high temperature
Summary
Compared with PPT, MPB would be a disadvantage at the Sn- and Zr-rich boundaries of BCTS or BCTZ ceramics, respectively, which would reduce TC and probably reduce the stability of the planar electro-mechanical coupling factor and piezoelectric properties with increasing temperature. This is not beneficial for lead-free piezoelectric ceramics applied in electrical devices at high temperature.
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