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Multiferroic ceramics of 0.675BiFe1-xCrxO3-0.325PbTiO3 (x = 0, 0.01, 0.025, 0.05) were prepared and comparatively investigated. The rhombohedral-tetragonal morphotropic phase boundary (MPB) was formed in 0.675BiFeO3-0.325PbTiO3. The B-site Cr-substitution changes the structure from MPB to rhombohedral phase gradually, accompanied with monotonously decreased ferroelectric Curie temperature and average grain size. More interestingly, Such Cr-substitution enhances room temperature ferroelectric and magnetic properties simultaneously. The underlying mechanism is mainly attributed to the substitution enhanced local Fe3+-Cr3+ magnetic interaction and the suppressed oxygen vacancy effect. We believe these results are helpful supplements for optimizing structures and room temperature multiferroic properties of BiFeO3-based materials.

This manuscript reports the structural and electrical properties of Lanthanum substituted strontium bismuth titanate with general formula SrBi4-xLaxTi4O15 (where 0 [less than or equal to] x [less than or equal to] 0.25), prepared by solid-state reaction route. X-ray diffraction study shows a single phase orthorhombic structure in all the compositions. It was also observed that the lattice parameter increases up to x = 0.15 and then decreases with further La content. The Raman spectra shows the distribution of lanthanum into the perovskite layers and (Bi2O2)2+ layers of SrBi4Ti4O15 ceramic. The temperature dependent dielectric study reveals that the transition temperature and maximum dielectric constant decreases with La content. The broadening of the phase transition was observed with La substitution due to the decrease in octahedral distortion. Impedance analysis confirms the presence of two semicircular arcs in doped samples, suggesting the existence of grain and grain-boundary conduction. The P-E loop study shows that both the remnant polarization (Pr) and the coercive field increases with the increasing La content up to x = 0.15 and thereafter decreases to lower values with further La content. Similar kind of trend is also observed in DC conductivity.

Bismuth layered-structure oxides in the Bi3Ti(TaxNb1-x)O9 quasi-binary system were synthesized by the conventional solid state reaction approach, and their ferroelectric and piezoelectric properties were evaluated together with the structures. The XRD analysis showed that all the ceramics were the single phase. It was found that the remnant polarization (Pr) reached a maximum of 4.2 µC/cm2 when x = 0.5 mol%. In addition, a bright up-conversional photoluminescence (UC) can be measured by partial substituting Er3+ for Bi3+. Under 980 nm radiation excitation, three emission bands located at green (534, 549 nm) and red (670 nm) wavelength regions were obtained at room temperature. These Er3+ doped Bi3Ti(Ta0.5Nb0.5)O9 based ferroelectrics could be used as a multifunctional material for a wide range of applications.

KTa0.63Nb0.37O3 and Cu doped KTa0.63Nb0.37O3 single crystals were grown by the Czochralski method. The phase, optical and electric properties were characterized. The differences of XRD and color for KTa0.63Nb0.37O3 and Cu doped KTa0.63Nb0.37O3 single crystals are observed. Emission bands corresponding to Cu0 and Cu+ except of emission bands originating from KTa0.6Nb0.4O3 host were observed in the emission spectra of the KTa0.63Nb0.37O3:Cu single crystals. On the basis of these differences, we speculate the dominating existence of Cu0 and residual existence of Cu+ in KTa0.63Nb0.37O3 single crystal. The existence of Cu0 in KTa0.63Nb0.37O3 single crystal influences the optical and dielectric properties of crystal. The higher dielectric constant of Cu doped KTa0.63Nb0.37O3 single crystal than that of pure KTa0.63Nb0.37O3 single crystal is induced by the decrease of the resistance of the grain.

The structural origin of high piezoelectricity in perovskite-type relaxor ferroelectrics is a fundamental issue that remains elusive for decades. In this study, high and unstable piezoelectricity for the poled ceramics, accompanied with a crossover from a nonergodic relaxor to an ergodic relaxor state at room temperature, has been observed for 0.95(Bi0.5Na0.5)1-x (Li0.5Sm0.5)xTiO3-0.05BaTiO3 ceramics with x = 0.06. The result suggests that the high piezoelectric activity origins from the electric field-induced-ordered nanodomains. The rapid loss of piezoelectricity stems from the reversibility of the ordered nanodomains after removing applied electric field.

Bismuth layer-structured ferroelectric (BLSFs) ceramics of Na0.5Bi4.5-x(Pr0.5Ce0.5)xTi4O15 (NBT-x(Pr, Ce), x = 0.000, 0.004, 0.008, 0.012) were prepared by a conventional solid-state reaction method, and the influence of (Pr, Ce) additive on the ferroelectric, dielectric, and photoluminescence properties of samples were investigated. It is found that all the samples have a bismuth oxide layered structure with a dense microstructure. After (Pr, Ce) doping, the samples showed a bright red photoluminescence. The sharp excitation peaks around 449, 480 and 491 nm correspond to the 3H4 [arrow right] 3P2, 3H4 [arrow right] 3P1 and 3H4 [arrow right] 3P0 transition, respectively. Upon the excitation of 492 nm light at room temperature, samples show two emission bands located at 611 and 656 nm, respectively. The strong red emission band centered at 611 nm is attributed to 1D2 [arrow right] 3H4 transition, and the weak red emission located 656 nm is due to the 1D2 [arrow right] 3H5 transition. In addition, it is an intrinsic ferroelectric and piezoelectric material, and the enhanced ferroelectric properties were obtained by (Pr, Ce) doping. At x = 0.004, the remnant polarization 2P r reaches 13.54 [mu]C/cm2, together with a high Curie temperature (T c = 662 °C) and activation energy of E a = 0.83 eV. As a multifunctional material, the (Pr, Ce)-modified NBT piezoelectric ceramic may be useful in white LEDs, sensor and optical-electro integration.

Bi0.9Gd0.1Fe0.9Co0.1O3 (BGFC) films were deposited successfully on Pt(111)/Ti/SiO2/Si(100) and SrRuO3 (SRO)/Pt(111)/Ti/SiO2/Si(100) substrates by radio frequency magnetron sputtering. Effects of sputtering power, buffer layer and film thickness on ferroelectric properties of the sputtered BGFC films were studied. X-ray diffraction demonstrated that all films had a single perovskite-type structure. Highly (012) and (024)-oriented BGFC films were formed on Pt(111)/Ti/SiO2/Si(100) and SRO/Pt(111)/Ti/SiO2/Si(100) substrates. The ferroelectric test indicated that the leakage current density of BGFC films sputtering at 40 W was smaller than that of BGFC films sputtering at 120 W, and its ferroelectric property was better than that of BGFC films sputtering at 120 W. Furthermore, the leakage current density of BGFC film with SRO buffer layer was improved and reduced by one order of magnitude under the same film thickness and sputtering power, comparing with the leakage current density of BGFC film without SRO buffer layer on Pt(111)/Ti/SiO2/Si(100) substrate. The ferroelectric property of BGFC thick film is better than that of BGFC thin film under the same sputtering power and applied electric field. The logJ-logE plots of BGFC films indicated that the leakage mechanisms of BGFC films with sputtering power of 40 and 120 W belong to the space-charge-limited conduction and Ohmic conduction, respectively. The mechanisms of the effects of sputtering power, buffer layer and film thickness on the ferroelectric properties of BGFC films were discussed.

A unique duplex structure (no grain with an intermediate size) was observed in dense KSr2Nb5O15 (KSN) ferroelectric ceramics, which were prepared by the solid-state reaction method using KSN microcrystalline as raw material. A combined experimental and computer simulation study confirmed that the few crystallographic orientations were existent for KSN grains and the adjacent grains were self-assembled by sharing a common orientation. This spontaneous oriented attachment resulted in the direct mergence of KSN grains, which were responsible for accelerating the bigger grains growth to form a duplex structure. This new understanding of the grain growth process could serve as a viable route to controlling density and grains sizes in the design of ferroelectric ceramics, particularly for textured ceramics.

In the present study, specimens of composition Ba1-xSrxTiO3 (x = 0.0, 0.05, 0.075, 0.10 & 0.15) were synthesized using mechanochemical activation technique and their structural, dielectric and ferroelectric characteristics were investigated for the major applications such as a multi-layered ceramic capacitor (MLCC) and microwave tunable devices. Structural analysis using X-ray diffraction pattern of the systems by Rietveld refinement confirms the formation of tetragonal phase with P4 mm space group. The intensity ratio of bonds and wave number shift in Raman spectra suggests little structural changes with strontium content. Microstructural investigation reveals that there is no appreciable change in grain size with increasing strontium concentration. The results on the variation of dielectric constant with temperature suggest the shifting of Curie temperature to lower temperature side with increasing strontium concentration. Current-voltage characteristics reveal that with increasing strontium content current increases which can be correlated with the observed variation of activation energy of the studied samples, which also decreases with the increasing concentration of strontium.