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It has been well known that BiFeO3 (BFO) exhibits two interesting physical properties simultaneously, which invoked multi-ferroic device applications to change electrical properties by controlling magnetic properties of BFO or vice versa. However, BFO has a high leakage current density, which may be attributed to bismuth and/or oxygen vacancies in the structure. In order to reduce the leakage current, a thin layer of dielectric SrTiO3 (STO) has been deposited on the top of BFO films by pulsed laser deposition. Improvement in leakage current and remnant polarization was observed in the STO capped BFO thin films. [ABSTRACT FROM AUTHOR]

The structural and electrical properties of BiFeO3 (BFO) and rare earth metal ions (Re) co-substituted (Bi0.9Re0.1)(Fe0.9Mn0.1)O3-δ (Re = Nd, Sm, Ce and Tb) thin films prepared on Pt(111)/Ti/SiO2/Si(100) substrates via a chemical solution deposition method were investigated. The significant decrease of leakage current density and improved ferroelectric properties were observed from the co-substituted thin films. The largest remnant polarization (2Pr) (61.7 μC/cm2) and the lowest coercive field (2Ec) 657 kV/cm at 931 kV/cm were measured from the (Bi0.9Ce0.1)(Fe0.9Mn0.1)O3-δ thin film. The leakage current density value of (Bi0.9Sm0.1)(Fe0.9Mn0.1)O3-δ thin film (3.29 × 10−5A/cm2) was found to be two order lower than that of the pure BFO. [ABSTRACT FROM AUTHOR]

The microstructure, dielectric and leakage current characteristics of Bi(Fe1-xTix)O3 (x = 0-0.2) polycrystalline ceramics have been investigated. Phase transformation from rhombohedral to orthorhombic symmetry occurs at around x∼0.2. Average grain size decreases rapidly and then saturates with the size of few μm above x = 0.025. The steplike decrease in ε for the composition of x = 0 and 0.01 are related dielectric relaxation. Leakage currents were much decreased by about 6 orders of magnitude above x = 0.025. Similarly to the results of SEM images and dielectric constants, leakage currents were changed with Ti substitution. [ABSTRACT FROM AUTHOR]

Dielectric and piezoelectric properties of lead-free (1-x)(Bi0.5K0.5)TiO3-xBiFeO3 ceramics prepared by a conventional solid-state reaction method were studied in the range of x = 0∼40 mol%. A tetragonal perovskite structure was maintained at x = 0∼10 mol% forming a solid solution between (Bi0.5K0.5)TiO3 and BiFeO3 with no secondary phase. Piezoelectric coefficient (d33) increased from 31 pC/N at x = 0 mol% to 64 pC/N at x = 6 mol% and then decreased with further addition of x. Depolarization temperature (Td) gradually decreased with increasing x from 302°C at x = 0 mol% to 163°C at x = 20 mol% and slightly increased up 180°C at x = 40 mol%. [ABSTRACT FROM AUTHOR]

Dielectric and piezoelectric properties of (Bi0.5K0.5+xLiy)TiO3 ceramics were studied in the range of x = -8-1 and y = 0-5 mol% of the stoichiometric K0.5. Secondary phases were not observed within -1 ≤ x ≤ 1 but started emerging at x ≤ -2 mol%. A tetragonal perovskite structure was maintained at all compositions despite the formation of secondary phases with K deficiency. Piezoelectric coefficient (d33) was improved due to K-vacancies facilitating domain walls movement and was further enhanced due to the microstructure improved with the tetragonality optimized by Li addition. Depolarization temperature (Td), on the other hand, depressed with K deficiency and Li addition. [ABSTRACT FROM AUTHOR]

A-site non-stoichiometric lead-free 0.93(K0.5Na0.5)(1 + x)NbO3-0.07LiNbO3 (KNNL) piezoelectric ceramics were prepared by a solid state reaction. The contents of both K and Na were simultaneously controlled to -4 mol% deficient. The K3Li2Nb5O15 second phase was observed in most of the composition except for 0 mol%. The polymorphic phase transition (PPT) between the tetragonal and orthorhombic phases was found from X-ray diffraction and temperature-dependent dielectric constant at around -2 mol%. With increasing (K+Na) ion deficiency, the PPT temperature of KNNL ceramics increased but Curie temperature (TC) decreased. The piezoelectric constant was 155 pC/N for nominally stoichiometric KNNL and decreased as decreasing (K+Na) content. [ABSTRACT FROM AUTHOR]

The effects of Bi(Zn0.5Ti0.5)O3 (BZT) substitution in BaTiO3 (BT) or (Bi0.5Na0.5)TiO3 (BNT) piezoelectric ceramics were studied. (1-x)BaTiO3-xBi(Zn0.5Ti0.5)O3 (x = 0.02, 0.04, 0.06, 0.08, 0.10, 0.20, 0.30, and 0.40) and (1-y)(Bi0.5Na0.5)TiO3-yBi(Zn0.5Ti0.5)O3 (y = 0, 0.01, 0.025, 0.05, 0.10, and 0.20) ceramics were prepared by a solid state reaction method. The structures and surface morphologies have been examined using an X-ray diffraction and scanning electron microscopy, respectively. The grain size and density increased with increasing the amount of BZT in both systems. Curie temperatures (TC) were decreased as BZT substituted. Piezoelectric properties also decreased with the substitution of BZT. [ABSTRACT FROM AUTHOR]

Ferroelectric CaBi4Ti4O15 (CBTi) thin films with random orientation and high c-axis orientation were prepared on a Pt(111)/Ti/SiO2/Si(100) substrate by a chemical solution deposition method. We observed a strong dependence of ferroelectric and dielectric properties on the film orientation. The CBTi thin film with random orientation exhibited remnant polarization (2Pr) of 54 μ C/cm2 at an applied electric field of 250 kV/cm and dielectric constant (ε) of 412 at a frequency of 1 kHz. The values of 2Pr and ε were larger than those observed in the CBTi thin film with high c-axis orientation. In addition, the randomly oriented thin film showed lower leakage current density than the highly c-axis-oriented thin film. [ABSTRACT FROM AUTHOR]

Cu-doped Ba0.7Sr0.3TiO3 (BST) thin films were prepared on Pt(111)/Ti/SiO2/Si(100) substrates by a sol-gel spin coating process. The coated thin films were annealed at 750°C for 3 min in oxygen, air and nitrogen atmospheres by a rapid thermal annealing process. All of the Cu-doped BST thin films were consisted of a single phase perovskite structure and exhibited smooth crack-free surfaces. We investigated the effects of the annealing atmosphere on the microstructure and the electrical properties of the Cu-doped BST films. The Cu-doped BST film by annealing in oxygen exhibits a dielectric constant of 923 with electric field dependent tunability of 48.6% at electric field 250 kV/cm and a leakage current density of 1.82 × 10- 5A/cm2 at electric field of 150 kV/cm. [ABSTRACT FROM AUTHOR]

A new type of bismuth-based relaxor, such as Bi 2 (Y 1/2 Nb 1/2 ) 2 O 7 and Bi 2 (Mg 1/3 Nb 2/3 ) 2 O 7 thin films were fabricated on Pt/Ti/SiO 2 /Si substrate by a sol-gel spin coating process. The films exhibit characteristic diffused phase transition. The temperature dependent reciprocal dielectric constant characteristics of the films deviates from the Curie-Weiss law in the temperature range over the dielectric constant maximum temperature ( T m ). The diffuseness of the phase transition of the thin films was estimated by calculating the difference between T m and T cw (starting temperature following the Curie-Weiss law). For the thin films annealed at 750°C, the temperature T m , the Curie-Weiss temperature Θ, the Curie-Weiss constant c and the temperature T cw were measured at frequency of 10 3 Hz, respectively. [ABSTRACT FROM AUTHOR]