Structure-property relationships in the lead-free piezoceramic system K0.5Bi0.5TiO3 - BiMg0.5Ti0.5O3

Abstract

Distinctive structure-property relationships are revealed in the relaxor ferroelectric ceramic solid solution, (1x)K 0.5 Bi 0.5 TiO 3 -xBiMg 0.5 Ti 0.5 O 3 : 0.02 < x < 0.08. The constructed phase diagram and results of in-situ synchrotron X-ray diffraction provide explanations for temperature and electric field dependent anomalies in dielectr ic, ferroelectric and electromechanical properties. At room temperature a mixed phase tetragonal and pseudocubic phase field occurs for compositions 0 > x ≤ 0.07. As temperature rises to ≥ 150 °C, the ferroelectric tetragonal relaxor phase changes to a pseudocubic ergodic relaxor phase; this change in length scale of polar order is responsible for an inflection in relative permittivity -temperature plots. The transitio n is reversed by a sufficient electric field, thereby explaining the constricted form of polarisation-electric field loops measured at >150°C. It is also responsible for a change in slope of the strain-electric field (S-E) plots which are relatively linear in the ferroelectric regime i.e. at temperatures up to 150 °C, giving unipola r strains of 0.11 % at 20 °C and 0.14% at 150 °C (50 kV cm -1 field). The additional contribution from the effect of the field-induced pseudocubic to tetragonal transition, generates strains of ~ 0.2 % at 185 °C.Unusual for a piezoelectric solid solution, the maximum strains and charge coefficients (d33 =150 pC N -1 , 20 °C) do not coincide with a morphotropic or polymorphic phase boundary.

Energy harvesting, electrical, and magnetic properties of potassium bismuth titanate-based lead-free ceramics

“…Perovskite-type ceramics ABO 3 are widely used in the electronics industry. Lead zirconate titanate (PZT) is an ABO 3 ceramic that is the most widely used piezoelectric ceramic owing to its excellent electrical properties [1][2][3]. However, since lead is hazardous and the toxicity of lead is recognized to be a serious problem, many lead-containing ceramics are banned [1,4].…”

“…Lead zirconate titanate (PZT) is an ABO 3 ceramic that is the most widely used piezoelectric ceramic owing to its excellent electrical properties [1][2][3]. However, since lead is hazardous and the toxicity of lead is recognized to be a serious problem, many lead-containing ceramics are banned [1,4]. Among others, the European Union has passed legislations limiting the amount of lead in electronics, with the exception of piezoelectrics until lead-free alternatives are available [5,6].…”

“…Moreover, BKT has also attracted interest because of its high depolarization temperature (T d ~ 250°C). This is good for the applications at high temperature such as in electromechanical devices which operate at high temperatures, for example in the fuel injection systems [1]. The BKT ceramic seems to be a candidate for lead-free piezoelectrics with a high T c and T d values.…”

“…d 33 and k p values, of the BKT ceramic. Structureproperty relationships of the lead-free (1-x)BKT-xBMT system were investigated by Zeb et al [1,23,24]. They reported that the BKT ceramic was modified by BMT, they obtained an improvement in the d 33 and room temperature electromechanical bipolar strains.…”

“…Since the BKT ceramic is an important lead-free material employed in actual applications [1,5,13], its modification is of considerable interest, and this ceramic is expected to exhibit better properties than those of the single phase. In the present research, the modification of the BKT ceramic by BNiT was achieved with the aim of improving its properties.…”