(Ba,Ca)(Zr,Ti)O3 lead-free piezoelectric ceramics—The critical role of processing on properties

Abstract

Lead-free piezoelectric compositions based on (Ba,Ca)(Zr,Ti)O 3 have been reported to exhibit many piezoelectric properties similar to the conventionally used Pb(Zr,Ti)O 3 materials, and have thus been attracting much attention as potential replacements for lead-based piezoceramics. However, there appears quite a wide variation in the reported piezoelectric properties of the BCZT ceramics, indicating that such properties may be sensitive to fabrication and processing methods. This paper reports an investigation of a wide range of processing factors, including composition (e.g. ratio of Ba(Zr,Ti)O 3 to (Ba,Ca)TiO 3 ), sintering conditions (temperature and cooling rate), particle size of the calcined ceramic powder, structure and microstructure (e.g. phase, lattice parameters, density and grain size), and their effect on the piezoelectric properties. For individual compositions, lattice constants and grain size, which are themselves dependent on the ceramic powder particle size and sintering conditions, have been shown to be very important in terms of optimising piezoelectric properties in these materials.

Phase transition and improved electrical performance of Ba0.85Ca0.15Zr0.1Ti0.9O3–Ca0.28Ba0.72Nb2O6 ceramics with high Curie temperature

“…ACCEPTED MANUSCRIPT 4 performances of BCZT ceramics after the addition of a tungsten bronze structure compound (TBC). TBC ferroelectrics are very attractive from the viewpoint of their potential application; they possess the chemical formula (A1) 2 (A2) 4 (C) 4 (B) 10 O 30 .…”

“…TBC ferroelectrics are very attractive from the viewpoint of their potential application; they possess the chemical formula (A1) 2 (A2) 4 (C) 4 (B) 10 O 30 . In this formula A are cations of the type Sr 2+ , Ba 2+ , Ca 2+ , Pb 2+ , K + , Na + or some rare earth cations occupying the sites A1 and A2; cations Nb 5+ , Ta 5+ occupy octahedral B sites;…”

“…However, high sintering temperatures (~1450 °C), low Curie temperatures (T c~8 0 °C), and weak temperature stabilities hinder their use in practical applications [4,5]. To date, considerable research has been carried out to optimize the synthesis and electrical performances of BZTxBCT based systems: by tuning the Ba/Ca or Zr/Ti ratio [6,7], by doping the metal oxide and sintering aids [2,5, 8], and by adapting new preparation techniques, such as hot-pressing and spark plasma sintering [4,9]. Unfortunately, any improvement in the electrical properties of these systems is usually derived at the expense of the sintering temperature and temperature stability, limiting their practical application.…”

Phase transitions and dielectric, ferroelectric and piezoelectric properties of Bi<inf>0.5</inf>(Na<inf>0.82</inf>K<inf>0.18</inf>)<inf>0.5</inf>TiO<inf>3</inf>-doped (Ba<inf>0.85</inf>Ca<inf>0.15</inf>)(Zr<inf>0.1</inf>Ti<inf>0.9</inf>)O<inf>3</inf> ceramics

“…2 (d)) the coercive electric field was increased. The reported coercive electric field values for pure 0.5BZT-0.5BCT [8] are much smaller than for 18BNKT [7] (about 0.5 and 1.7 kV/mm respectively). Therefore, in the temperature range 80-110 °C (Fig.…”

“…1 (c)). This may imply 3 corresponding phase transitions, including 2 ferroelectric-ferroelectric and 1 ferroelectricparaelectric transitions [8]. The transition around 90 °C is indicative of the T c , where the remanent polarization dropped to zero as the structure became cubic.…”