Articles you may be interested inSymmetry determination on Pb-free piezoceramic 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 using convergent beam electron diffraction method J. Appl. Phys. 115, 054108 (2014) Temperature dependent dielectric permittivity studies demonstrated frequency independent behavior, indicating that the studied sample was not a typical relaxor ferroelectric. A polymorphic phase transition between rhombohedral and tetragonal phase was noticed near room temperature followed by a tetragonal to cubic transition with 97 C as the temperature of maximum permittivity. The macroscopic values of d 33 and d 31 were $350 pC/N and À141 pm/V, whereas the electromechanical coupling factors k p and k t were 44.5% and 41.6%, respectively. Bulk P-E hysteresis loop was obtained with saturation polarization 11 lC/cm 2 and coercive field $4 kV/cm. Distinct polarization contrast with a complex mosaic-like domain structure was observed in the out-of-plane mode of piezoresponse force microscopy. The domain width and the correlation length were estimated to be nearly 2 lm and 827 nm, respectively. Local hysteresis loop with apparent coercive voltage, V c ¼ 15.8 V, was observed. V C 2013 AIP Publishing LLC. [http://dx

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.

Lead-free 0.5BaZr0.2Ti0.8O3–0.5Ba0.7Ca0.3TiO3 (BZT–BCT) thin films were deposited on Pt(1 1 1)/TiO2/SiO2/Si substrates by pulsed laser deposition. The optimal ferroelectric response with a high saturation polarization Ps ~ 110 µC cm−2, remnant polarization Pr ~ 32.5 µC cm−2 along with a coercive field of 0.18 MV cm−1 was observed from the P–E hysteresis loops under an applied frequency of 1 kHz. A giant recoverable energy-storage density of 93.52 J cm−3 at an applied electric field ~3.47 MV cm−1 was observed. The optimized BZT–BCT thin films exhibited a high dielectric constant with a low dielectric loss at room temperature like their bulk counterpart (high dielectric constant (Ɛ ~ 121 81)) and low dielectric loss (tan δ ~ 0.01–0.03) properties. OPP-PFM images revealed switchable ferroelectric distinct polarization contrasts on the application of a  ±12 V dc voltage on the conductive tip at room temperature. Observed enhanced dielectric, ferroelectric and energy density properties of BZT–BCT thin films are useful for next generation electrical energy storage applications.

Pristine (BiFeO3), Pr and Sc co-substituted Bi0.9Pr0.1Fe1−x Sc x O3 (0.01 ⩽ x ⩽ 0.07) ceramics have been investigated for their structural (including x-ray diffraction and Raman), morphological and piezoresponse behaviour. Secondary phases observed in pristine BiFeO3 (BFO) ceramic were significantly suppressed in the co-substituted samples. Grain size decreased in the co-substituted samples. Raman study revealed ten active phonon modes which remained almost invariant with co-substitution. Out-of-plane piezoresponse (OPP-PFM) exhibited negative self-polarization effect in the virgin state (without any poling) which has been explained in terms of built-in electric field. The self-polarization effect is largest in 3% Sc co-substituted sample. Poling with ±30 V dc voltage demonstrated both positive and negative domains. Maximum difference in the peak values (from histograms) of such opposite domains was observed in the Bi0.9Pr0.1Fe0.99Sc0.01O3 sample. Information from local measurements (such as PFM) should be useful in deciding such multiferroic materials for device application.

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