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Barium titanate ceramic BaTiO3 (BT) has been investigated extensively because of scientific interest as well as various applications to electronic devices. When pure BaTiO3 is highly resistive at room temperature (ρ > 1010 Ωcm). However its electrical resistivity can be dramatically lowered by some dopants, like rare earth elements [1, 2]. In the present research lanthanum-doped BT ceramics described by the general formula Ba1-x La x Ti1-x/4O3, for x = 0.001 and x = 0.003, was prepared by free sintering method. The electrical properties of (BLT) materials were studied by impedance spectroscopy with a Quadtech 1920-type precision LCR meter and parameters of the phase transition were determined. The equivalent circuit method was applied to fit the experimental data. The possibility of application of La-doped BT ceramics for fabrication of piezoresistive transducers sensitive for small stress load are also discussed in the present paper. [ABSTRACT FROM PUBLISHER]

P-E hysteresis loops of PZT and 0.9PZT - 0.1BLT ceramics were determined using a modified Sawyer-Tower circuit. Ferroelectric properties investigation of the PZT and 0.9PZT - 0.1BLT ceramics under stress levels in the range of 0-175 MPa was also carried out. The result showed that with increasing stress level, a reduction of remanent polarization was clearly observed. The result was interpreted in terms of non-180° ferroelectric domain switching processes and the decrease in switchable part of domains induced by stress applied to these materials. [ABSTRACT FROM AUTHOR]

Synopsis: Phase transitions in Bi4 - xLaxTi3O12 (BiLT-x) mixed crystals with the low La concentration (x < 0.5) were investigated. It was found that the dielectric anomaly showing the phase transition appears below 675°C where the transition temperature depends on the concentration x, while the transition at 675°C remains in the concentration range of 0 ≤ x ≤ 0.5. The spontaneous polarization along the c-axis at room temperature was found to decrease as the La concentration increases and to disappear at about x = 0.2. New phase transition from the orthorhombic to the monoclinic phase in the BiLT-x was experimentally confirmed. The phase transition and its symmetry change were discussed on the basis of the Landau theory. [ABSTRACT FROM AUTHOR]

Ferroelectric (Bi,La)4Ti3O12 (BLT) thin films were prepared on a p-type Si (100) wafer with a SrTa2O6 (STA) buffer layer for a metal-ferroelectric-insulator-silicon (MFIS) structure. The STA buffer layer was completely crystallized at the high temperature over 800°C. We observed that STA thin films fabricated at 900°C for 3 minutes in O2 ambient had good insulating properties. Their EOT value was about 5.7 nm. Considering the distribution of the bias voltage on a series capacitor, the ferroelectric BLT and the dielectric STA, BLT thin films with a different thickness were formed on STA/Si structures and characterized by C-V measurement including memory windows. It was found that the memory window width was about 1.5 V for the ±5 V bias sweeping with the 600 nm thick BLT films on STA/Si structure. The leakage current density was about 1.0 × 10-7 A/cm2 at 5 V. These results are useful and promise the realization of a MFIS structure with the BLT and a STA layer for non-destructive read-out (NDRO) type ferroelectric memories. [ABSTRACT FROM AUTHOR]

Bimuth(Bi) excessed and vanadium(V)-doped Bi 3.25 +x La 0.75 Ti 2.97 V 0.03 O 12 (BLTV) ceramics were prepared by a solid state reaction. Crystallized single-phases with Bi-layered perovskite structure were confirmed by X-ray diffraction. The low frequency dielectric dispersion was decreased, and the conductivity was decreased for the Bi-excessed BLTV ceramics of x = 0.05–0.10. The V doping improved the ferroelectric properties and decreased the conductivity. The effects of V-doping on ferroelectric and electrical properties on Bi-excessed BLTV ceramics were investigated. [ABSTRACT FROM AUTHOR]

The Bi-excess Bi 3.25+ x La 0.75 Ti 3 O 12+δ (x = 0, 0.05, 0.10, 0.15, 0.20, BLT) thin films were prepared by pulsed laser deposition. Single phases of BLT thin films was confirmed by X-ray diffraction. For the small Bi-excess BLT films, ferroelectric properties are improved. One of them, 10 mol% Bi-excess BLT films exhibits high remanent polarization, low leakage current density, and improved switching polarization. Influence of Bi excess on ferroelectric and electrical properties are investigated by ferroelectric P-E hysteresis loops, transient current, and leakage current. [ABSTRACT FROM AUTHOR]

Ferroelectric Bi 3.35 La 0.75 Ti 3 O 12 (BLT) film was prepared by using a sol-gel method on Pt electrode with (Cr, Ti)N/TiN/Ti barrier layers. The BLT films crystallized by conventional annealing conditions (700°C, 30 min, 0.8°C/sec, O 2 ) showed hysteretic polarization-voltage ( P-V ) curves, but the leakage current density was high. Thus, a flash-annealing method (750°C 30 sec, 70°C/sec, O 2 ) was attempted to minimize the thermal budget to the ferroelectric films and the underlying structures. It was found in this method that the leakage current was remarkably decreased from 40.9 μA/cm 2 to 322 nA/cm 2 at an applied voltage of 3 V. Furthermore, X-ray diffraction peak intensity of the perovskite-type BLT phase was much stronger in the BLT film crystallized by the flash-annealing method. [ABSTRACT FROM AUTHOR]

Ferroelectric Bi 4-x La x Ti 3 O 12 (BLT) thin films with various compositions (x=0.65, 0.70, 0.75) were prepared on Pt/Ti/SiO 2 /Si substrate by MOD method. SEM showed uniform surfaces composed of rod-like grains after annealing at 650. The Bi 3.30 La 0.70 Ti 3 O 12 thin film capacitor showed better ferroelectric properties than other films with different compositions. The remanent polarization and the coercive field of Bi 4-x La x Ti 3 O 12 (x=0.70) thin film were 31.3 C/cm 2 and 117.2kV/cm, respectively. Moreover the capacitor did not show any significant fatigue up to 3×10 10 switching cycles at 5V. [ABSTRACT FROM AUTHOR]

The effect of excess Bi content on (Bi,La) 4 Ti 3 O 12 (BLT) thin film fabricated by sol-gel synthesis was investigated. The films were formed on Pt/IrO 2 /SiO 2 /Si. Excess Bi promoted the formation of a secondary phase around BLT particles during the crystallization process, and this secondary phase promoted the crystallization and grain growth of the film and improved its ferroelectric properties. A BLT thin film crystallized at 600°C had good ferroelectric properties: its remanent polarization was 26.2 μC/cm 2 and its coercive field was 53.1 KV/cm. After 10 9 switching cycles, its remanent polarization had decreased less than 10%. [ABSTRACT FROM AUTHOR]

(Bi,La) 4 Ti 3 O 12 /Pb(Zr,Ti)O 3 /(Bi,La) 4 Ti 3 O 12 multilayer thin films were prepared on Pt/Ti/SiO 2 /Si substrates by a chemical solution deposition method, with the intention of combining the good ferroelectric properties of PZT thin films and good fatigue-free characteristics of BLT thin films. The multilayer structure showed fatigue-free characteristics at least up to 10 10 switching bipolar pulse cycles under 8 V, excellent retention properties, and well-defined hysteresis loops with the remanent polarization (2Pr) of 8.8 μC/cm 2 and the coercive field (Ec) of 47 kV/cm. [ABSTRACT FROM AUTHOR]