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Er½Na½TiO3–Bi½Na½TiO3 solid solutions were prepared by a sol–gel technique. The complex distortion of the rhombohedral structure of host Bi½Na½TiO3 compounds was obtained caused by the addition of the solid solution of Er½Na½TiO3 into the host Bi½Na½TiO3 matrix. The random incorporation of Er3+ cations into the host crystal of the Bi½Na½TiO3 material resulted in reducing its optical band gap from 3.04 to 2.79 eV by increasing the Er½Na½TiO3 amount. The strong green emission at 550 nm was obtained at room temperature and is related to the emission of Er3+ cations from 4S3/2 to 4I15/2 levels. The observation of strong photoemissions at room temperature of Er½Na½TiO3-Bi½Na½TiO3 binary system promises to create the next generation of smart electronic devices. [ABSTRACT FROM AUTHOR]

The mixed spinel—ilmenite nanocomposites of (1 − x)NiTiO3–xCoFe2O4 (x = 0, 0.05, and 0.10) have been synthesized by sol–gel method. In a one-pot synthesis method, both the constituent phases of composites are formed during the same time of the synthesis process. X-ray powder diffraction gave evidence of the phase purity of the systems. CoFe2O4 phase modified the optical band gap of NiTiO3 materials, shifted the optical band-gap value NiTiO3 toward lower energy. Optical band-gap values decreased from 2.23 to 1.51 eV for pure NiTiO3 and 10 mol% CoFe2O4-modified NiTiO3 samples, respectively. NiTiO3–CoFe2O4 composites with 5 and 10 mol% CoFe2O4 fractions were found to enhance the ferroelectric and magnetic properties of NiTiO3 at room temperature. The remanent polarization (Pr) increased from 0.017 to 0.182 µC/cm2 and saturation polarization (Ps) increased from 0.056 to 0.219 µC/cm2 for NiTiO3 and 10 mol% CoFe2O4-modified NiTiO3 sample, respectively. The saturation magnetization (Ms) and remanent magnetization (Mr) of the samples increased with increasing of CoFe2O4 fraction. The increasing of Ms and Mr of composites indicated the strong dependence of magnetic properties on CoFe2O4 addition. [ABSTRACT FROM AUTHOR]

In this report, solid solutions of (1−x)Bi1/2Na1/2TiO3+xSrNiO3-δ materials were synthesized by a chemical method. X-ray diffraction and Raman scattering were used to study the structural properties of the (1−x)Bi1/2Na1/2TiO3+xSrNiO3-δ solid solutions. All studied samples had rhombohedral symmetry, where the Sr and Ni cations tended to randomly incorporate with the host Bi1/2Na1/2TiO3 lattices during the formation of solid solutions. The random incorporation of Sr and Ni cations into the host lattices resulted in structural distortion and reduced the optical band gap from 3.04 eV for the pure Bi1/2Na1/2TiO3 to 2.63 eV for the 9 mol.% SrNiO3-δ-modified Bi1/2Na1/2TiO3 sample. The complex magnetic properties of (1−x)Bi1/2Na1/2TiO3+xSrNiO3-δ system were investigated as a function of SrNiO3-δ concentrations. We expected that our simple and flexible method could be used to integrate the ferromagnetic properties in current advanced functional lead-free materials. [ABSTRACT FROM AUTHOR]

The NiTiO3 ceramic was synthesized in nanostructured form by citrate gel method. The phase structure, microstructure and magnetic properties of synthesized compounds were investigated by X-ray diffraction (XRD), scanning electron microscope and vibrating sample magnetometer. Williamson–Hall plot was used to calculate the crystallite size and microstrain of sample. The XRD analysis showed the formation of rhombohedral crystal structure of synthesized powders. The crystallite size is about 35 nm and microstrain is 5. 9 × 1 0 − 4 . The optical band gap was estimated from UV-Visible spectrum with value of 2.43 eV. The NiTiO3 samples showed coexistence of ferroelectric and antiferromagnetic properties at room temperature. [ABSTRACT FROM AUTHOR]

A new (1-x)Bi0.5Na0.5TiO3 + xMgCoO3-δ solid solution system was synthesized using the simple sol–gel method. The structure that was investigated via X-ray diffraction and Raman scattering analysis indicated that the MgCoO3-δ materials were highly soluble into the host Bi0.5Na0.5TiO3 crystals. The random incorporation of Mg and Co cations into the host crystal of the Bi0.5Na0.5TiO3 materials reduced the optical band gap energy and induced a complex magnetic behavior as a function of MgCoO3−δ concentration solute in the host matrix. The optical band gap energy values decreased from 3.05 eV for pure Bi0.5Na0.5TiO3 materials to 2.22 eV with 9 mol% MgCoO3-δ solution for the Bi0.5Na0.5TiO3 compounds. A weak ferromagnetic property with strongly induced diamagnetism was obtained at room temperature for the pure Bi0.5Na0.5TiO3 materials, whereas ferromagnetic properties were observed for the MgCoO3-δ-modified Bi0.5Na0.5TiO3 compounds. The addition of paramagnetic and/or antiferromagnetic-like behavior was obtained for the MgCoO3-δ solid solution with over 5 mol% in the host Bi0.5Na0.5TiO3 materials. This work contributes to the current understanding of the interaction of transition metal cations in the host crystal ABO3 perovskite of lead-free ferroelectric materials due to the co-modification of A and B sites. [ABSTRACT FROM AUTHOR]

We reported the room-temperature ferromagnetism in iron doped Bi 0.5 K 0.5 TiO 3 nanocrystals. The reduction of band gap from 3.31 eV to 2.27 eV was obtained after introduction of iron to Bi 0.5 K 0.5 TiO 3 with concentration up to 7 mol%. The first-principles density function theory (DFT) calculations indicate that the reduction of band gap is due to the presence of conduction bands of iron, and the ferromagnetism in iron-doped Bi 0.5 K 0.5 TiO 3 samples was explained by the exchange splitting between spin subbands through crystal field theory. This method may provide an available way to get single-phase multiferroics and resolve the problem of the scarcity of single-phase multiferroics in nature. [ABSTRACT FROM AUTHOR]

• New (1 − x)Bi 0.5 Na 0.5 TiO 3 + x CaMnO 3- δ solid solution compounds was synthesized. • Ferromagnetism ordering at room temperature in Bi 0.5 Na 0.5 TiO 3 samples was enhanced via CaMnO 3- δ -modified. • The E g values of Bi 0.5 Na 0.5 TiO 3 compounds decreased with increasing amount of CaMnO 3- δ. • A -site and B -site-co-modified Bi 0.5 Na 0.5 TiO 3 in the magnetic and optical properties were discussed. CaMnO 3- δ -modified Bi 0.5 Na 0.5 TiO 3 was fabricated by using a sol–gel method. In the modified Bi 0.5 Na 0.5 TiO 3 , a single perovskite with distorted structure was obtained due to the random distribution of Ca and Mn cations in the host lattice. The co-modification in A - and B -sites of Bi 0.5 Na 0.5 TiO 3 via Ca and Mn resulted in the reduction of optical band gap and induction of room-temperature ferromagnetism. Co-modification of A - and B -sites in lead-free ferroelectric Bi 0.5 Na 0.5 TiO 3 is suitable for fabricating smart materials in electronic devices. [ABSTRACT FROM AUTHOR]

The new Bi0.5Na0.5TiO3-SrMnO3−δ solid solution materials were fabricated via sol–gel method. The random incorporation of Sr and Mn cations into host lattice of Bi0.5Na0.5TiO3 resulted in structural distortion and influenced on the reduction of the optical band gap from 3.07 eV to 1.81 eV for pure Bi0.5Na0.5TiO3 and 9 mol% SrMnO3−δ solid solution into Bi0.5Na0.5TiO3. The magnetic properties of Bi0.5Na0.5TiO3 materials at room temperature were tuned via compensation of diamagnetic material with weak-ferromagnetism to ferromagnetism with low SrMnO3−δ content and combination of paramagnetism/antiferromagnetism-like and ferromagnetism with higher SrMnO3−δ content solid solution in Bi0.5Na0.5TiO3. The tunable magnetic and optical properties of lead-free ferroelectric materials was promising for their application to green electronic devices. [ABSTRACT FROM AUTHOR]

SrFeO 3-δ -modified Bi 0.5 Na 0.5 TiO 3 materials were fabricated by a sol–gel method. SrFeO 3-δ materials existed as a well solid solution in Bi 0.5 Na 0.5 TiO 3 materials, resulting in the random distribution of Sr and Fe cations into the lattice of the host. The impurities of Sr and Fe cations preferred to substitute at the A -site and B -site in Bi 0.5 Na 0.5 TiO 3 materials, respectively. These cations distorted the structure of the host materials due to differences in the radius of the cations of impurity and the host. The modified materials showed reduced optical band gap and strongly induced ferromagnetism at room temperature. This work presents a new method for integrating room-temperature ferromagnetism in lead-free ferroelectric materials to overcome the limitations of single transition metals as dopants. [ABSTRACT FROM AUTHOR]

In this work, the Sm 1/2 Na 1/2 TiO 3 -addition Bi 1/2 Na 1/2 TiO 3 materials as solid solutions were synthesized via a chemical route method. The X-ray diffraction and Raman scattering results indicated that Sm 1/2 Na 1/2 TiO 3 materials were well solute into the host Bi 1/2 Na 1/2 TiO 3 materials to form solid solutions. The optical bandgap of the pure Bi 1/2 Na 1/2 TiO 3 materials was estimated from ultraviolet–visible spectroscopy of 3.07 eV. The bandgap slightly reduced to 2.94 eV as increasing the Sm 1/2 Na 1/2 TiO 3 amounts up to 9 mol.%. Strong photoluminescence (PL) of Sm 1/2 Na 1/2 TiO 3 -addition Bi 1/2 Na 1/2 TiO 3 materials was obtained in the visible wavelength range of 550–750 nm which related to photoluminescence of Sm cations randomly incorporated into the host lattice of Bi 1/2 Na 1/2 TiO 3 materials. Our work was promised to show a new method to integrate the PL properties in lead-free ferroelectric materials. • New solid solution (1− x)Bi 1/2 Na 1/2 TiO 3 + x Sm 1/2 Na 1/2 TiO 3 materials was synthesized. • The optical band gap energy of Bi 1/2 Na 1/2 TiO 3 materials were complex changed. • The strong photoemission properties were obtained for 5 mol.% Sm 1/2 Na 1/2 TiO 3 -modification Bi 1/2 Na 1/2 TiO 3 compounds. • This work demonstrated a new method to integrate photoemission in lead-free ferroelectric materials. [ABSTRACT FROM AUTHOR]