Properties Of Lead-free Materials Research Articles

Improvement in piezoelectric performance of the lead-free BiFeO3-BaTiO3 ceramics by synergistic approach

High-piezoelectric properties in lead-free materials have been the pursuit for both industry and scientific research. In this work, the synergistic approaches of phase/domain engineering and novel poling method are adopted for the improvement of piezoelectric performance. The strategically designed lead-free donor-doped BiFeO3-xBaTiO3 ceramics at the crystal structure morphotropic phase boundary (MPB) between the rhombohedral and tetragonal phases exhibited a high Curie temperature (TC ≥ 450 °C). Furthermore, simultaneously enhanced static piezoelectric constant (d33) of 436±5 pC/N and thermally stable dynamic piezoelectric constant (d33*) of 550±10 pm/V were achieved. The high piezoelectric performance is collectively attributed to the crystal structure MPB, thermal quenching effect, local structure heterogeneity induced by donor doping, mesoscale nanodomains, and novel poling method inside a magnetic field. The temperature-insensitive and high piezoelectric performance of the current work is superior to the other lead-free piezoceramics. The synergistic approach for the improvement of piezoelectricity provides a path for the development of lead-free ceramics for high-temperature commercial applications.

Lead-free piezoelectrics: Current status and perspectives

In the last few years, there has been tremendous effort to develop lead-free ferroelectric ceramics with high piezoelectric properties by various doping and alloying routes. Several material systems have been explored, however, no prominent alternative to the versatile lead zirconate titanate (PZT) system has been found yet. Despite the achieved improvement in piezoelectric properties, there are problems in the synthesis, processing and poling of the sintered ceramics. Various processing techniques including microwave, hydrothermal, sol–gel, Pechini and spark plasma sintering have been used to overcome the drawbacks related to synthesis issues. In this paper, an attempt is made to review recent developments on lead-free piezo materials emphasizing their preparation, structure–property relations, and consequent physical properties. In this context, both compositional and structural engineering approaches to achieve acceptable piezoelectric properties in lead-free materials are discussed. Piezoelectric properties of the most promising lead-free compositions/families including titanates, alkaline niobates and bismuth perovskites and their solid solutions, along with non-perovskites such as bismuth layer-structured ferroelectrics are reviewed in detail. A brief coverage of the recent developments in the area of piezoelectric energy harvesting is also encompassed.

Ultrasonic Investigation of Field-Induced Piezoelectric Properties in Lead Free Materials

Ultrasonic method was applied for evaluation of piezoelectricity in layered crystals of CuInP2S6 family and of La(Mg1/2Ti1/2)O3-BaTiO3 (BT-LMT) electroceramics. Amplitude of electric signal appearing on the plate under ultrasonic excitation is proportional to appropriate piezoelectric constant. In CuInP2S6 family piezosensitivity was observed only in low temperature phase. In BT-LMT ceramics piezosensitivity had anomalies at low temperature phase transitions and had long tails in the high temperature paraelectric phase. Field-induced hysteresis loops of such ultrasonically detected piezoelectric signal amplitude in the ferroelectric phase were observed. In the paraelectric phase field-induced piezosensitivity due to electrostriction appeared in layered crystals and BT-LMT ceramics when DC bias electric field was applied. In centrosymetric AgInP2Se6 crystals comparatively large piezoelectric sensitivity was induced due to electrostriction by DC bias electric field applied along c-axis.