Lead zirconate titanate (PZT) based piezoelectric materials are well known for their excellent piezoelectric properties. However, considering the toxicity of lead and its compounds, there is a general awareness for the development of environmental friendly lead-free materials as evidenced from the legislation passed by the European Union in this effect. Several classes of materials are now being considered as potentially attractive alternatives to PZTs for specific applications. In this paper, attempts have been made to review the recent developments on lead-free piezo materials emphasizing on their preparation, structure–property correlation, etc. In this context, perovskite systems such as bismuth sodium titanate, alkali niobates (ANbO3), etc. and non-perovskites such as bismuth layer-structured ferroelectrics are reviewed in detail. From the above study, it is concluded that some lead-free compositions show stable piezoelectric responses even though they do not match the overall performance of PZT. This has been the stimulant for growing research on this subject. This topic is of current interest to the researchers worldwide as evidenced from the large number of research publications. This has motivated us to come out with a review article with a view that it would give further impetus to the researchers already working in this area and also draw the attention of the others.

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Review: environmental friendly lead-free piezoelectric materials

Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol–gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual...

Solution Combustion Synthesis of Nanoscale Materials

Ferroelectric composites are now an established alternative to conventional ferroelectric ceramic materials and to the more recently discovered ferroelectric polymers. These materials due to their unique blending of polymetric properties of mechanical flexibility, formability and low cost with high electro-active properties have been been suggested to be a viable alternative both in piezoelectric and pyroelectric transducer applications. This review is devoted to the piezoelectric and pyroelectric properties exhibited by these type of composites with a special reference to those made of ceramic particles embedded in a polymer matrix (i.e. 0-3 connectivity type composite). A review of models predicting the electro-active properties of 0-3 composites is presented together with a proposal for a new mixed connectivity cubes model to be applicable to the case of high ceramic loading and/or when the ceramic grain size incorporated in the polymer matrix is comparable to the thickness of the sample. A review of the experimental results of the piezo- and pyroelectric properties of various ferroelectric composite materials, reported by several workers, is also presented in this paper. Special reference is made to composites made from calcium modified lead titanate and poly(vinyldene fluoride-trifluorethylene) emphasizing their advantages in the poling process which is a critical phase in the process of obtaining successful electro-active 0-3 composite electrets.

Inorganic ceramic/polymer ferroelectric composite electrets

Ce-doped strontium bismuth titanate (SrBi4Ti4O15, SBT) powders were prepared
 by glycine-nitrate process at 400-500°C and the ceramics were sintered at
 980°C. The phase composition, morphology and electric properties were
 investigated. It was found that the calcined powders consist of a single
 phase SBT and the calcination temperature is lower than that for the
 conventional solid state method. The morphology of Cedoped SBT is flake-like
 and the layer size decreases with Ce-addition from 12 to 2μm confirming
 that the addition of Ce3+ inhibits grain growth. The Curie temperature of
 Ce-doped SBT increased for about 20°C compared to the pure SBT. The tan δ
 was ~0.005 at 35°C and even below 0.05 up to 400°C. The temperature
 coefficient of dielectric constant was ~0.012 and the rate of frequency
 change was 0.01-0.04, which indicated the high stability of dielectric
 properties of the Ce-doped SBT. Impedance analysis revealed that the
 conduction mechanism of the Ce-doped SrBi4Ti4O15 ceramics is mainly grain
 conduction.

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Microstructure evolution and dielectric properties of Ce-doped SrBi4Ti4O15 ceramics synthesized via glycine-nitrate process

Impact of Eu3+ ion substitution on structural, magnetic and microwave traits of Ni–Cu–Zn spinel ferrites

Cerium modified bismuth titanate ceramics were studied as potential lead-free ferroelectric materials over a broad temperature range. Polycrystalline samples of Bi4−xCexTi3O12 (x = 0.2, 0.4, 0.6, 0.8) (BCeT) were prepared using the solution combustion technique. The effect of Ce doping on their crystalline structure, ferroelectric properties and electrical conduction characteristics were explored. An increase in the dielectric constant and decrease in loss tangent is observed due to addition of Ce in bismuth titanate lattice up to a certain threshold doping concentration. The presence of pyrochlore phase decreases the density of ceramics with composition x = 0.8 which may be due to grain inhibitor property of Ce. The value of remnant polarization increases with increasing doping content up to x = 0.6 due to decrease in defect sites in the samples, further increase in cerium content induces leakage current which makes the sample lossy. The real–imaginary impedance plots are interpreted using RC model, this explains the contribution of the grain-bulk and the grain boundary resistivities to the total resistivity of the materials. Activation energy increases with increasing Ce concentration indicating a decrease in defect sites due to which the conductivity of the doped ceramics reduces.

Impedance analysis and dielectric properties of Ce modified bismuth titanate lead free ceramics synthesized using solution combustion route

Nd and Nb doped sodium bismuth titanate ceramics have been synthesized and characterized. Structural properties were obtained based on the XRD pattern analysis, indicating rhombohedral symmetry at room temperature. Impedance and conductivity (DC and AC) studies were done on polycrystalline samples. The results indicate that DC and AC conduction occurs by different mechanism in each case. The possible mechanism in the present case is discussed.

Impedance spectroscopy and conductivity studies on B site modified (Na0.5Bi0.5)(NdxTi1 − 2xNbx)O3 ceramics

Optical properties and preparation of Bismuth Titanate (Bi12TiO20) using combustion synthesis technique

Study of Maxwell–Wagner (M–W) relaxation behavior and hysteresis observed in bismuth titanate layered structure obtained by solution combustion synthesis using dextrose as fuel

Strontium bismuth niobate (SrBi2Nb2O9 (SBN), K0.025Sr0.95Gd0.025Bi2Nb2O9 (KSGBN1), K0.05Sr0.9Gd0.05Bi2Nb2O9 (KSGBN2) and K0.1Sr0.8Gd0.1Bi2Nb2O9 (KSGBN3)) ceramics were prepared by two stage solid s...

G.S. Kumar

Papers

Impedance analysis and dielectric properties of Ce modified bismuth titanate lead free ceramics synthesized using solution combustion route

Impedance spectroscopy and conductivity studies on B site modified (Na0.5Bi0.5)(NdxTi1 − 2xNbx)O3 ceramics

Optical properties and preparation of Bismuth Titanate (Bi12TiO20) using combustion synthesis technique

Study of Maxwell–Wagner (M–W) relaxation behavior and hysteresis observed in bismuth titanate layered structure obtained by solution combustion synthesis using dextrose as fuel

Synthesis, Impedance and Dielectric Studies of Double Doped Strontium Bismuth Niobate Ferroelectric Ceramics