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Abstract: Lead calcium titanate ceramics modified by partial substitution of rare earths for lead, particularly, (Pb, Sm, Ca)(Ti, Mn)O3 ceramics, were explored for their structural, dielectric and piezoelectric properties. These modified ceramics with a composition of Pb0.76−3x/2Sm x Ca0.24Ti0.98Mn0.02O3 (x =0−0.08) were prepared by solid state reaction route. The XRD study showed single-phase formation with tetragonal structure. Lattice anisotropy (c/a) was found to decrease from 1.057 to 1.023 with increase in Sm substitution from 0 to 8mol%, respectively. Microstructural study revealed the average grain size between 1.2 and 2.2μm. The relative density was found to increase from 95% to 98.4% with increase in samarium substitution from 0 to 8mol%, respectively. Detailed dilatometric study was performed in order to study the shrinkage behaviour during the sintering schedule. The maximum shrinkage was found to occur between 900°C and 1100°C. The dielectric constant (ɛ′) and loss (tan δ) for all the compositions were investigated over a wide frequency (100Hz to 1MHz) and temperature (25–450°C) range. The room temperature (25°C) dielectric constant was found to increase from 130 (at 10kHz) for pure lead calcium titanate sample to 380 (at 10kHz) for 8mol% samarium substituted sample and also showed a decreasing trend with increase in the frequency for all the substitutions (0–8mol% Sm). Curie temperature, T C (determined from the plot of ɛ′ vs. temperature) and tan δ were found to decrease with increasing samarium content. The Curie temperature was found to decrease from 348°C to 192°C for 0–8mol% Sm substitutions, respectively. Piezoelectric coefficients were also measured at room temperature. Electromechanical anisotropy (k t/k p) was observed to increase from 11.7 (0mol% Sm) to 27 (8mol% Sm). Piezoelectric anisotropy (d 33/d 31) was also observed to increase from 22.5 for un-substituted sample to 28 for the sample substituted with 8mol% samarium. The experimental results successfully showed that samarium substitution not only reduces the lattice anisotropy but also helps in improving piezoelectric properties. [Copyright &y& Elsevier]

Abstract: 0.5(PbNi1/3Nb2/3)O3–0.5Pb(Zr0.32Ti0.68)O3 (PNN–PZT) ceramics were successfully prepared from a mechanochemical activation-assisted method (MAAM), which skips the calcination step(s) at an intermediate temperature which is otherwise required for solid state reaction. A detailed investigation has been carried out on the structural and piezoelectric properties of these samples. Improvement in piezoelectric properties was observed in PNN–PZT ceramics processed by mechanochemical activation-assisted method. The value of piezoelectric charge coefficient (d 33) is ∼710pC/N for PNN–PZT ceramics processed by mechanochemical activation-assisted method, which is higher than ceramics obtained by solid state reaction (615pC/N), with improvement of about 15.45%. The value of strain is also higher (0.21%) for mechanochemical activation-assisted method whereas it is 0.15% for ceramics obtained by solid state reaction at 40kV/cm. [Copyright &y& Elsevier]

Abstract: Ceramic samples of the nominal composition Ba(Zr x Ti1−x )O3 (x =0.15) were synthesized by the solid-state reaction method and the sintering was done in two different atmospheres—air and oxygen. Oxygen sintering resulted in samples with dense microstructures. Low field dielectric measurements showed an increase in the values of dielectric constants over the entire temperature range of measurement, in the oxygen-sintered samples. Similarly, polarization–electric field (P–E) hysteresis measurements indicated a marked increase in the value of remnant polarization in them. [Copyright &y& Elsevier]

Polycrystalline ceramic samples with compositional formula Ba 0 · 90 Sr 0 · 10 Ti 1-3x/4 Fe x O 3 (x = 0, 0.01 and 0.015) 'BTSF' were prepared by the conventional solid state reaction method. The phase confirmation was done by using X-ray diffraction 'XRD' technique. Tetragonality 'c/a' was found to be decreased with Fe3+ substitution. Dielectric constant 'ε' and tangent loss 'tanδ' was measured as a function of temperature at different frequencies (1, 10, 40, 80 and 100 kHz). The value of ε and tanδ at 30 °C for BTSF0 sample was found to be 2300 and 4.5% (at 100 kHz), whereas for BTSF2 sample it was 3170 and 2.3% (at 100 kHz). The dielectric results indicate the prepared samples can be the potential candidates for capacitive applications. The P-E hysteresis loops for all samples were recorded at different temperature. The remnant polarization 'P r ' and coercive field 'E c ' was found to be decreased with an increase in temperature for all the samples. Electrocaloric effect 'ECE' was observed in BTSF2 sample. The value of ΔT max was found to be 1.06 K at 25 kV/cm, and the value of the electrocaloric coefficient § max was found to be 0.0424 K cm kV−1. The high value of § max implies that BTSF2 ceramics can be used in potential applications like future solid-state refrigeration technologies. • Tetragonality of BST ceramics decreases with increase in Fe-content. • Dielectric constant and tangent loss improves with an increase in Fe-content. • A large value of adiabatic ΔT = 1.06 K was observed in BTSF2 sample. • The electrocaloric strength is very large (0. 0424 K cm kV-1) in BTSF2 sample. [ABSTRACT FROM AUTHOR]

Highlights: [•] BPZT ceramics were prepared by normal and two-stage sintering technology. [•] Comparative study of impedance of BPZT was done. [•] Enhancement in the grain and grain boundary resistivity is observed. [Copyright &y& Elsevier]

Abstract: Nanocrystalline lithium zinc ferrites substituted with cobalt were synthesized by the citrate precursor method. X-ray diffraction was used to confirm the spinel phase. Mössbauer studies at room temperature were carried out to study the effect of cobalt concentration on the various hyperfine interactions. Variation of the saturation magnetization with respect to composition was discussed. The result shows some anomalous behaviour when cobalt is substituted to lithium ferrite in presence of zinc. [Copyright &y& Elsevier]

Crystalline samples of 0.6Bi 1- x Nd x FeO 3 -0.4PbTiO 3 , or (BNFPT) x , were produced using the solid-state reaction technique with x = 0.05, 0.10, 0.15, and 0.20. The structural analysis revealed a structural transition from rhombohedral to tetragonal induced by Nd doping, which was further confirmed by Rietveld refinement analysis. The average grain size decreases from 1.46 µm to 1.09 µm with increasing Nd concentration. A ferroelectric relaxor-type behavior of the samples is observed as Nd content rises. The magnetization increases with increasing Nd doping concentration, caused by structural distortion and partial destruction of the spin cycloidal structure of BiFeO 3. The temperature-dependent magnetization is found to decrease with increasing temperature and is an irreversible effect. Leakage current is reduced by three orders of magnitude, from 10−3 to 10−6, with Nd doping for the studied doping concentrations. An enhanced polarization–electric field (P-E) hysteresis loops have been observed with a low value of remnant polarisation as Nd concentration increases. The P-E loops show s that the energy storage density of the BFO-PTO solid solution rises with increasing Nd concentration up to 0.15 and then decreases. The maximum recoverable energy storage density (W rec) and efficiency (η) for the 0.15 composition are 4.54 mJ/cm3 and 79 %, respectively. Conversely, as the concentration of Nd rises, the piezoelectric coefficient falls and follows the opposite trend as that of energy storage density. The magnetoelectric (ME) coupling coefficient increases with Nd doping. These results suggest that the investigated materials may be suitable for memory and energy storage devices. • 0.60BiFeO 3 - 0.40PbTiO 3 solid solution with varying Nd compositions have been prepared by solid state reaction method. • Rietveld refinement study revealed the coexistence of tetragonal and rhombohedral structures simultaneously • Nd doping exhibits an anomaly in the dielectric constant (ε) is a signature of magnetoelectric (ME) coupling. • The magnetic properties and magnetoelectric properties were greatly enhanced with the increasing Nd content. • The maximum energy storage density and efficiency for a 0.15 composition are 4.54mJ/cm3 and 79% respectively. [ABSTRACT FROM AUTHOR]

The standard solid state reaction method has been used to synthesize solid solution 0.8Bi 1- x Nd x FeO 3 –0.2PbTiO 3 where x = 0.05, 0.10, 0.15 and 0.20 (BNFPT) x. The effect of Nd3+substitution on magnetic, ferroelectric, dielectric, and structural properties of 0.8BiFeO 3 -0.2PbTiO 3 (BNFPT) x have been studied. The X-Ray Diffraction and Raman study of the samples revealed that the tetragonal structure with P4mm space group and rhombohedral structure with R3c space group exists simultaneously. The SEM study reveals uniform grain scattering. The 0.8BiFeO 3 -0.2PbTiO 3 compound with Nd doping exhibits an increase in dielectric constant and reduce dielectric loss with respect to temperature and frequency. These features make the material as a promising candidate for the development of electronic device. At room temperature, all prepared samples exhibit weak ferro-magnetic behavior. However, a steady increase in residual magnetization was observed at 5 K. The magnetization result was found to be better than that of other rare earth doped BiFeO 3 -PbTiO 3 solid solution. Ferroelectric study of the sample ascertained the pinning effect with low residual polarization in hysteresis loops. The reduction of leakage current with Nd doping is promising candidate for range of applications. • Nd doped BiFeO 3 - PbTiO 3 solid solution with varying Nd compositions have been prepared by solid state reaction method. • The X-Ray Diffraction and Raman study revealed the coexistence of tetragonal and rhombohedral structures simultaneously. • Nd doping exhibits an increase in dielectric constant and reduce dielectric loss with respect to temperature and frequency. An anomaly in the dielectric constant (ε) is a signature of magnetoelectric (ME) coupling. • The magnetic properties were greatly enhanced with the increasing Nd content. • The reduction of leakage current with Nd doping is promising candidate for range of applications. [ABSTRACT FROM AUTHOR]

• Squareness S around 0.442 is achieved for CFMO3 at 2 K. • Rietveld refinement of XRD patterns confirms the pure phase cubic crystal structure. • Decrease in lattice parameters is also observed with Mo doping. • DFT calculation validates the experimental results of the base sample. [Display omitted] Structural and low temperature magnetic properties of CoFe 2− x Mo x O 4 (x = 0.01, 0.03 and 0.05) were studied in the present work. Rietveld refinement of XRD patterns of CoFe 2− x Mo x O 4 (x = 0.01, 0.03 and 0.05) confirm the pure phase cubic crystal structure in Fd3m space group. The decrease in lattice parameters (a contraction of the lattice) has been observed with doping, which confirms the probability of substitution of 'Mo' at the octahedral site of parental CoFe 2 O 4 (CFO). The micro-strain via W-H plots was found to be enhanced for CoFe 1.95 Mo 0.05 O 4 (CMFO5) sample which confirms the incorporation of 'Mo' atoms at Fe-site and subsequently reducing impurities as observed from refined patterns. The low temperature (2K) magnetic parameters were found to be greatly enhanced with 'Mo' substitution. We observed the decrease in anisotropy constant of Co2+ ions with 'Mo' doping and Mo6+ ions concentration at the tetrahedral site of CFO, increases the magnetization of the samples. Both M-H and ZFC-FC measurements confirm the ferrimagnetic behavior of all the samples. The maximum value of information storage parameter 'S' achieved around 0.442 for x = 0.03 sample at 2K. The structural parameters, electronic (density of states and band structure) and magnetic properties of pure CFO have also been investigated via computational first principle based density functional theory (DFT) calculations. The computational results are in good agreement with the experimental outputs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Maximum relative density (95.64%) and Pr (52μC/cm2) can be observed for x =0.02. [•] P r/P s ratio indicating squareness of the PE loop found to be maximum for x =0.015. [•] P r/P s =0.83 is not reported in the literature for the PZT ceramics. [Copyright &y& Elsevier]

• Temperature coefficient (Tcc) is above 10%. • The value of tanδ is very small all over the temperature range. • The tetragonality decreases with Sm3+ and Fe3+ substitution. • Room temperature dielectric constant increases. Polycrystalline ferroelectric ceramics with compositional formula Ba 0.70−x Ca 0.30 Sm x Ti 1−x Fe x O 3 (BCSTF) with (0, 0.005, 0.010, 0.015 and 0.020) were prepared by solid state reaction route and sintered at 1325 °C for 4 h. Single perovskite phase with tetragonal structure was confirmed from X-ray diffraction (XRD) analysis. The dielectric constant 'ε' and tangent loss 'tanδ' were studied for all the samples as a function of frequency (100 Hz to 100 kHz) and temperature (30–200 °C). A very small low 'tanδ' (0.9% at 100 kHz) was observed. The high value of temperature coefficient of capacitance 'Tcc' (~10%) was observed for all the BCSTF samples. P-E hysteresis loops were recorded for sample with x = 0.020 at different temperature. Electrocaloric effect 'ECE' was investigated and the temperature change 'ΔT' was found to be 0.53 K at 35 kV/cm with a high value of electrocaloric coefficient (0.15 K m/MV). The results show that the prepared ceramics can be useful in applications such as capacitor, dielectric bolometers, electrocaloric applications. [ABSTRACT FROM AUTHOR]

Abstract: Barium titanate is one of the most studied ferroelectric materials which has been used in various forms, e.g. bulk, thin and thick films, powder, in a number of applications. In order to achieve a material with desired properties, it is modified with suitable substituents. Most common substituents have been strontium, calcium and zirconium. Here, we report studies on lead and zirconium substituted barium titanate. The material series with compositional formula Ba0.80Pb0.20Ti1−x Zr x O3, with x varying from 0 to 0.1, was chosen for investigations. The material was synthesized by solid-state reaction method. Reacted powders compacted in the form of circular discs were sintered at 1300°C. All the samples were subjected to X-ray diffraction (XRD) analysis and found to have single phase perovskite structure. Dielectric behavior was studied as a function of frequency and temperature. Curie temperature (T c) was found to decrease with increasing x. [Copyright &y& Elsevier]

Abstract: Samarium modified lead zirconate titanate (PSZT: Pb1−x Sm x (Zr0.65Ti0.35)O3: x =0, 0.02, 0.04, 0.06) ceramics were synthesized by solid state ceramic route. XRD shows single-phase formation with rhombohedral structure up to x =0.04. With Sm—substitution, the grain size first increases up to x =0.02 and then decreases. A metal/ferroelectric/metal (MFM) structure was made by depositing gold electrode on the flat surfaces for electrical measurements. All samples show normal ferroelectric behaviour, however, a squareness of P–E loop (polarization vs. electric field) was observed to increase with Sm content. Higher electromechanical coupling coefficients (K p and K t) have been achieved for the PZT with 6mol% Sm substitution and having fine grain size. [Copyright &y& Elsevier]