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We have evaluated the ferroelectric and electrical properties of pure BiFeO3(BFO) and (Bi0.9Ho0.1)(Fe0.975Ti0.025)O3+δ(BHFTO) thin films on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method. The improved electrical properties were observed in the BHFTO thin film. The leakage current density of the co-doped BHFTO thin film showed three order lower than that of the pure BFO, 1.22 × 10−6A/cm2at 100 kV/cm. The remnant polarization (2Pr) and the coercive electric field (2Ec) of the BHFTO thin film were 61 μC/cm2and 1190 kV/cm at an applied electric field of 800 kV/cm and at a frequency of 1 kHz and these values decreased with increasing measurement frequency, 35 μC/cm2and 920 kV/cm at 10 kHz, respectively. Also, the 2Prand the 2Ecvalues were fairly saturated above 30 kHz. [ABSTRACT FROM PUBLISHER]

Multiferroic Bi(Fe0.9Mnx0.1)O3(x= 2+, 3+, and 4+) thin films were prepared on Pt(111)/Ti/SiO2/Si(100) substrates by using a pulsed laser deposition method. The effects of different oxidation states of Mn used as a starting material on crystal structure, leakage current, dielectric, and ferroelectric properties were investigated. No significant change in the crystal structure was observed while electrical properties were affected by the oxidation states of Mn. A frequency-dependent dielectric relaxation region was observed in the films with Mn3+and Mn2+, indicating the presence of space charges such as oxygen vacancies. [ABSTRACT FROM AUTHOR]

Effects of heat-treat procedure and sintering temperatures were investigated in 0.67Bi1.05FeO3-0.33BaTiO3ceramics. The structure, dielectric, ferroelectric, and piezoelectric properties of ceramics made by normal cooling or quenched cooling process were investigated. All ceramics show single pseudo-cubic perovskite crystal structure. Although the structure was not changed but other properties were much changed by heat-treatment. The normally cooled ceramic showed ‘pinched’ ferroelectric hysteresis loops with remanent polarization value of about 10 μC/cm2. On the contrary, the quenched ceramic showed ‘normal’ ferroelectric hysteresis loops with remanent polarization value of about 17 μC/cm2. The piezoelectric constantd33value of 13 pC/N in normally cooled ceramic was improved to 39 pC/N in quenched ceramic. These improved results were attributed to the reduced populations of defects made during the heat-treatments. [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]

Randomly oriented and c-axis-oriented Bi3.15Pr0.85Ti3O12 (BPT) thin films were prepared by a chemical solution deposition method. Ferroelectric and leakage current properties were strongly related to the crystallographic orientation of BPT thin film. The values of remnant polarization (2Pr) and leakage current density were 74 μC/cm2 at 250 kV/cm and 3.4 × 10-8 A/cm2 at 125 kV/cm for the randomly oriented thin film, respectively, and 16 μC/cm2 and 6.9 × 10-6 A/cm2 for the c-axis-oriented thin film, respectively. The result indicates that the polarization vector of BPT thin films is not oriented along the c-axis. [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]

Effects of Bi(Zn0.5Ti0.5)O3 (BZT) substitution in Pb(Zr1-xTix)O3 (PZT) piezoelectric ceramics were investigated. Morphotropic phase boundary was observed at x = 0.48 and high piezoelectric properties were observed similarly to the un-substituted PZT ceramics. Piezoelectric properties were improved with 5 mol% BZT substitution. The ferroelectric transition temperatures were decreased by about 45°C with 5 mol% BZT substitution contrary to the increase of the transition temperature with BZT substitution in PbTiO3. [ABSTRACT FROM AUTHOR]

5 mol % La3 +, Nd3 + or Y3 +-cosubstituted BiFe0.97Cr0.03O3 thin films (denoted by BLaFCr, BNdFCr, and BYFCr, respectively) have been successfully deposited on Pt (200)/TiO2/SiO2/Si substrates by a chemical solution deposition method. Well-saturated ferroelectric hysteresis loops and low leakage current densities have been observed in BLaFCr, BNdFCr, and BYFCr thin films with single-phase structure. The values of remanent polarization (Pr) and coercive field (Ec) were 64 μ C/cm2 and 275 kV/cm, 61 μC/cm2 and 290 kV/cm, and 31 μ C/cm2 and 315 kV/cm for BLaFCr, BNdFCr and BYFCr thin films at the maximum electric field of 712 kV/cm, respectively. In the present study, the differences in values of Pr seem to be related to the doped ionic radii. [ABSTRACT FROM AUTHOR]