Enhanced temperature stability and quality factor with Hf substitution for Sn and MnO2 doping of (Ba0.97Ca0.03)(Ti0.96Sn0.04)O3 lead-free piezoelectric ceramics with high Curie temperature

In this work, the process of two-stage modifications for (Ba0.97Ca0.03)(Ti0.96Sn0.04-xHfx)O-3 (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 (T-C) of about 112 degrees C, a piezoelectric charge constant (d(33)) of 313 pC/N, an electromechanical coupling factor (k(p)) of 0.49, a mechanical quality factor (Q(m)) of 122, and a remnant polarization (P-r) of 19 mu C/cm(2). In addition, the temperature stability of the resonant frequency (f(r)), k(p), and aging d(33) could be tuned via Hf content. Good piezoelectric temperature stability (up to 110 degrees 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 degrees C, k(p) similar to 0.39, d(33) similar to 230 pC/N, Q(m) similar to 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)O-3 ceramics suitably adjusts the compositions for applications in piezoelectric motors and actuators. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).