Effects of TiO2 Seeding Layer on Crystalline Orientation and Ferroelectric Properties of Bi3.15Nd0.85Ti3O12 Thin Films Fabricated by a Sol–Gel Method

The effect of a 20-nm thick TiO₂ seeding layer on the growth of a Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) thin film on Pt(111) thin-film substrates has been studied. Under otherwise identical deposition process conditions, the BNT film could be turned from a highly random orientation to a (200) preference orientation by adding the seeding layer. Field-emission scanning electron microscope result reveals that the BNT thin film with the TiO₂ seeding layer is composed of fine grains with smaller sizes about 80–150 nm in diameter. The P _r and E _c values of the BNT thin film and BNT film with the TiO₂ seeding layer were 36 and 16 μC/cm², and 96.9 and 92 kV/cm at a voltage of 12 V, respectively. The fatigue test exhibited a very strong fatigue endurance up to 10⁹ cycles for both films. The leakage current densities were generally in the order of 10⁻⁶–10⁻⁵ A/cm² for both samples.     

Flexible Dielectric Bi1.5Zn1.0Nb1.5O7 Thin Films on a Cu-Polyimide Foil

Flexible thin films of Bi_1.5Zn_1.0Nb_1.5O₇ (BZN) were deposited on a Cu/polyimide (PI) foil by aerosol deposition at room temperature. The BZN film thickness was in the range of 1.2–17.9 μm. Highly dense and nanocrystalline films were obtained without any heat treatment. The dielectric constant and loss of the film at 100 kHz were over 150 and 0.04, respectively. Furthermore, the as-deposited film showed markedly low leakage current densities of <10⁻⁹ A/cm² at 3.0 V. These reasonably high dielectric properties were due to the nanocrystallinity of the films. The results confirm the significant potential of the BZN films as passive components in flexible printed circuit board applications.     

Fabrication and Electrical Properties of Textured Sr0.53Ba0.47Nb2O6 Ceramics by Templated Grain Growth

Textured Sr_0.53Ba_0.47Nb₂O₆ ceramics with a relative density of >95% were fabricated using templated grain growth (TGG). Acicular KSr₂Nb₅O₁₅ template particles synthesized via a molten salt process were aligned by tape casting in a mixture of solid-state-synthesized SrNb₂O₆ and BaNb₂O₆ powders. The resulting ceramics possessed strong fiber texture along the polar axis ([001]) of the strontium barium niobate. Samples with 15.4 wt% templates attained a textured fraction of 0.82 after sintering at a temperature of 1450°C for 4 h. These materials showed peak dielectric constants of 7550 at 1 kHz, remanent polarizations of 13.2 μC/cm², saturation polarizations of 21 μC/cm² (60%–85% of the single-crystal value), piezoelectric strain coefficients of 78 pC/N (70%–85% of the single-crystal value), and room-temperature pyroelectric coefficients of 2.9 × 10⁻²μC·(cm²·°C)⁻¹ (52% of the single-crystal value). These results show that TGG is a viable option for accessing single-crystal properties in polycrystalline ceramics.     

Preparation of 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 Thin Films Via a Polyvinylpyrrolidone-Assisted Aqueous Sol–Gel Process and Dielectric Properties

Pb(Mg_1/3Nb_2/3)O₃–PbTiO₃ (PMN–PT) thin films were prepared by spin coating using aqueous solutions of metal salts containing polyvinylpyrrolidone, where niobium oxide layers and lead—magnesium–titanium oxide layers were laminated on Pt(111)/TiO _x /SiO₂/Si(100) substrates and fired at 750° or 800°C. 250 ± 20 nm thick 0.7PMN–0.3PT thin films of a single-phase perovskite could be prepared, and the film fired at 750°C had dielectric constants and dielectric loss of 1900 ± 350 and 0.13 ± 0.03, respectively, exhibiting polarization-electric field hysteresis with a remanent polarization of 5.1 μC/cm² and a coercive field of 21 kV/cm.     

Sol—Gel Fabrication of Pb(Zr0.52 Ti0.48)O3 Thin Films Using Lead Acetylacetonate as the Lead Source

Lead zirconium titanate (PZT) thin films of the morphotropic phase boundary composition [Pb(Zr_0.52Ti_0.43)O₃] were deposited on platinum-coated silicon by a modified sol-gel process using lead acetylacetonate as the lead source. The precursor solution for spin coating was prepared from lead acetylacetonate, zirconium n -butoxide, and titanium isopropoxide. The use of lead acetylacetonate instead of the widely used lead acetate trihydrate provided more stability to the PZT precursor solution. Films annealed at 700°C for 12 min formed well-crystallized perovskite phase of Pb(Zr_0.52Ti_0.48)O₃. Microstructures of these films indicated the presence of submicrometer grains (0.1 to 0.2 μm). The dielectric constant and loss values of these films measured at 10 kHz were approximately 1200 and 0.04, respectively, while the remanent polarization and coercive field were ∼ 13 μC/cm² and ∼ 35 kV/cm. Aging of the solution had almost no effect on the dielectric and ferroelectric properties of these films.     

Excimer Laser Crystallized (Pb,La)(Zr,Ti)O3 Thin Films

A KrF pulsed excimer laser (248 nm) was utilized to crystallize sputtered La-modified Pb(Zr,Ti)O₃ (3:30:70) (PLZT) films on LaNiO₃-coated silicon substrates. The film surface was irradiated with defocused laser pulses in an oxygen ambient at various substrate temperatures. Polycrystalline, phase pure perovskite PLZT thin films were produced for substrate temperatures of 250°C and higher. The dielectric constant and loss tangent values of laser-assisted crystallized (10 min exposure at 10 Hz using a substrate temperature of 400°C) PLZT thin films at 10 kHz were 406 and 0.027; in comparison, rapid thermal annealed films (annealed at 700°C for 1 min) showed values of 400 and 0.021, respectively. Laser crystallized films exhibited a remanent polarization value of 14 μC/cm² with a coercive field |( E _+c+ E _−c)|/2 of 95 kV/cm.     

Damage-Free and Short Annealing of Pb(Zr,Ti)O3 Thick Films Directly Deposited on Stainless Steel Sheet by Aerosol Deposition with CO2 Laser Radiation

Pb(Zr,Ti)O₃ (PZT) thick films directly deposited onto stainless steel (SS) sheets by the aerosol deposition method were annealed by CO₂ laser (CL) radiation. The surface brilliance of the SS sheets was not influenced by thermal heating and the temperature of the reverse side of the film (i.e., the SS sheet) was measured at 150°C or less. The remanent polarization, coercive field values, and the dielectric constant are 27.8 μC/cm², 31.6 kV/cm, and 1366, respectively. The diffusion layer between the PZT and the SS sheet was minimized by the use of CL radiation compared with using an electric furnace.     

Preparation of Sputtered (Bax,Sr1−x)TiO3 Thin Films Directly on Copper

(Ba_0.6,Sr_0.4)TiO₃ (BST) films were deposited on copper foils by radio frequency magnetron sputtering. By the use of controlled p O₂ high-temperature anneals, the films were completely crystallized in the absence of substrate oxidation. X-ray diffraction and transmission electron microscopy (TEM) revealed an abrupt Cu/BST interface. The deposited BST films exhibit a zero bias permittivity and loss tangent values of 600 and 0.018, respectively. An electrical tunability ratio of 3.5:1 is observed on these metal–insulator–metal devices. Devices show leakage currents of 10⁻⁸ A/cm² at ±10 V/μm, and loss tangents as low as 0.003 in fields approaching 40 V/μm.     

Physical and Dielectric Properties of (1–x)PbZrO3·xBaTiO3 Thin Films Prepared by Chemical Solution Deposition

Physical and dielectric properties of (1– x )PbZrO₃· x BaTiO₃ thin films prepared by a chemical coating process have been investigated as a function of BaTiO₃ ( x ) content (0≤ x ≤0.2). Changing the molar ratio between propylene glycol and water prior to the deposition optimized the chemical precursors. (1– x )PbZrO₃- x BaTiO₃ thin films that contained a majority of perovskite phase, but also contained large amounts of other phases, were fabricated. These films could withstand fields of 250 kV/cm at 1 kHz. The microstructure of the thin films was found to depend on the BaTiO₃ content. The phase transition from antiferroelectric to ferroelectric was gradually induced as the BaTiO₃ content increased. A maximum dielectric constant of ∼809 was obtained at the composition of x = 0.1. A maximum dielectric constant of ∼809 was obtained at the composition of x = 0.1. A thin film at the low-field antiferroelectric-ferroelectric phase boundary with x = 0.05 exhibited the highest P _sat and P _r values. The maximum values of these were 45 and 31 μC/cm², respectively.     

Highly Oriented, Chemically Prepared Pb(Zr, Ti)O3 Thin Films

We have fabricated highly oriented, chemically prepared thin films of Pb(Zr_0.04Tio._0.60)O₃ (PZT 40/60) on both insulating and conducting substrates. While (100) MgO single crystals were used as the insulating substrates, the conducting substrates. were fabricated by RF magnetron sputter deposition of 100-nm-thick (100) Pt films onto (100) MgO substrates. For comparison, we also fabricated PZT 40/60 films that had no significant preferential orientation on platinized MgO substrates. Sputter deposition of an underlying amorphous Pt film was used to fabricate randomly oriented PZT 40/60 films. Highly (001) oriented PZT 40/60 films had higher remanent polarization (61 μC/cm² compared to 41 μC/cm²) and lower relative dielectric constant (368 compared to 466) than PZT 40/60 films that were randomly oriented.     

Effects of Excess Bi2O3 on the Ferroelectric Behavior of Nd-Doped Bi4Ti3O12 Thin Films

Effects of excess Bi₂O₃ content on formation of (Bi_3.15Nd_0.85)Ti₃O₁₂ (BNT) films deposited by RF sputtering were investigated. The microstructures and electrical properties of BNT thin films are strongly dependent on the excess Bi₂O₃ content and post-sputtering annealing temperature, as examined by XRD, SEM, and P – E hysteresis loops. A small amount of excess bismuth improves the crystallinity and therefore polarization of BNT films, while too much excess bismuth leads to a reduction in polarization and an increase in coercive field. P – E loops of well-established squareness were observed for the BNT films derived from a moderate amount of Bi₂O₃ excess (5 mol%), where a remanent polarization 2P _r of 25.2 μC/cm² and 2E _c of 161.5 kV/cm were shown. A similar change in dielectric constant with increasing excess Bi₂O₃ content was also observed, with the highest dielectric constant of 304.1 being measured for the BNT film derived from 5 mol% excess Bi₂O₃.     

Fatigue-Free Lead Zirconate Titanate (Pb(Zr,Ti)O3)-Based Capacitors Co-modified by Lanthanum and Lithium for Nonvolatile Memories

Pb_0.98(La_{1− x} Li _x )_0.02(Zr_0.55Ti_0.45)O₃(PLLZT with 0.1 ≤ x ≤ 0.7) thin films were sol-gel-grown on Pt(111)/Ti/SiO₂/Si substrates, employing a thin lead zirconate titanate (PZT) template layer. Films annealed at >550°C showed a highly (111)-oriented preferential growth. Typical values of the switchable remanent polarization (2 P _r) and the coercive field ( E _c) of the PLLZT/PZT/Pt film capacitor for x = 0.3 were 50 μC/cm² and 39 kV/cm, respectively, at 5 V. All the PLLZT/PZT/Pt capacitors (for 0.1 ≤ x ≤ 0.7) exhibited fatigue-free behavior up to 6.5 × 10¹⁰ switching cycles, a quite stable charge retention profile with time, and high 2 P _rvalues, all which assure their suitability for nonvolatile ferroelectric memories.     

In-Plane Polarized 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 Thin Films

Ferroelectric 0.7Pb(Mg_1/3Nb_2/3)O₃–0.3PbTiO₃ (PMN-PT) thin films were deposited on ZrO₂/SiO₂/silicon substrates using a chemical-solution-deposition method. Using a thin PZT film as a seed layer for the PMN-PT films, phase-pure perovskite PMN-PT could be obtained via rapid thermal annealing at 750°C for 60 s. The electrical properties of in-plane polarized thin films were characterized using interdigitated electrode arrays on the film surface. Ferroelectric hysteresis loops are observed with much larger remanent polarizations (∼24 μC/cm²) than for through-the-thickness polarized PMN-PT thin films (10–12 μC/cm²) deposited on Pt/Ti/Si substrates. For a finger spacing of 20 μm, the piezoelectric voltage sensitivity of in–plane polarized PMN-PT thin films was ∼20 times higher than that of through-the-thickness polarized PMN-PT thin films.     

Fabrication and Properties of Sol–Gel-Derived BiScO3–PbTiO3 Thin Films

BiScO₃–PbTiO₃ (BSPT) thin films near the morphotropic phase boundary were successfully fabricated on Pt(111)/Ti/SiO₂/Si substrates via an aqueous sol–gel method. The thin films exhibited good crystalline quality and dense, uniform microstructures with an average grain size of 50 nm. The dielectric, ferroelectric, and piezoelectric properties of the sol–gel-derived BSPT thin films were investigated. A remanent polarization of 74 μC/cm² and a coercive field of 177 kV/cm were obtained. The local effective piezoelectric coefficient d ^*₃₃ was 23 pC/N at 2 V, measured by a scanning probe microscopy system. The dielectric peak appeared at 435°C, which was 80°C higher than that of Pb(Ti, Zr)O₃ thin films.     

Characterization of the Thermally Contracting Tungstates Ta22W4O67, Ta2WO8, and Ta16W18O94

An investigation of the properties of high-purity (>99 wt%) tantalum tungstates (Ta₂₂W₄O₆₇, Ta, WO₈, and Ta₁₆W₁₈O₉₄) included determination of density (bulk and theoretical), refined lattice constants, maximum use temperatures, micro-hardness, heat capacity, thermal expansion (contraction) and diffusivity, calculated thermal conductivity, and electrical resistivity. Usable to ∼ 1700 K in air or inert atmospheres, these tantalum tungstates have theoretical densities of 7.3 to 8.5 g/cm³, are relatively soft (120 to 655 kg/mm² hardnesses), and are electrical insulators (6× 10³ to 2× 10⁸Ω^.cm resistivities). The distinguishing properties of the materials are their thermal expansion (average CTE values from + 0.6×10⁻⁸/K to −5.1× 10⁻⁶/K at 293 to 1273 K), thermal expansion hysteresis with minimal observable microcracking, and thermal diffusivity     

Porous Glass-Ceramics with a Skeleton of the Fast-Lithium-Conducting Crystal Li1+xTi2−xAlx(PO4)3

Porous glass-ceramics with a skeleton of the fast-lithium-conducting crystal Li_{1+ x} Ti_{2− x} Al _x (PO₄)₃ (where x = 0.3–0.5) were prepared by crystallization of glasses in the Li₂O─CaO─TiO₂─Al₂O₃–P₂O₅ system and subsequent acid leaching of the resulting dense glass-ceramics composed of the interlocking of Li_{1+ x} Ti_{2− x} Al _x (PO₄)₃ and β-Ca₃(PO₄)₂ phases. The median pore diameter and surface area of the resulting porous Li_{1+ x} Ti_{2− x} Al _x (PO₄)₃ glass-ceramics were approximately 0.2 μm and 50 m²/g, respectively. The electrical conductivity of the porous glass-ceramics after heating in LiNO₃ aqueous solution was 8 × 10⁻⁵ S/cm at 300 K or 2 × 10⁻² S/cm at 600 K.     

Physical Properties of Quenched Glasses in the Li2O-ZrO2-SiO2 System

The behavior and some physical and thermal properties of a 30Li₂O-70SiO₂ base glass composition with addition of ZrSiO₄ in the as-quenched state was investigated with the aid of X-ray diffraction (XRD), differential thermal analysis (DTA), thermal expansion and microhardness measurements, as well as density measurements. Transparent glasses prepared by the addition of ZrSiO₄ up to 10.30 mol% were obtained. ZrSiO₄ was found to decrease the expansion coefficient of the investigated glasses from 11.0 × 10⁻⁶ to 7.96 × 10⁻⁶°C⁻¹. The glass transition and softening point temperatures of the glasses showed a reverse behavior. On the other hand, both hardness and density increased for successive increases of the ZrSiO₄ amounts, with the highest values of 6.3 GPa and 2.65 g/cm³, respectively.     

Pyroelectric and Dielectric Properties of Mn Modified 0.82Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3 Lead-Free Thick Films

MnO-doped 0.82Bi_0.5Na_0.5TiO₃–0.18Bi_0.5K_0.5TiO₃(NBT–KBT) thick films with thickness about 40 μm have been prepared using screen printing on Pt electroded alumina substrates. The strong pyroelectric coefficient of 3.8 × 10⁻⁴ C·(m²·°C)^–1 was observed in 1.0 mol% MnO-doped-thick films, and the calculated detectivity figure of merit as high as 1.1 × 10⁻⁵ Pa^−0.5, which can be comparable to that of the commonly used lead based materials. The enhancement of the pyroelectric performances is attributed to the reductions in dielectric constant and loss and the improvements in the pyroelectric coefficient, which can be ascribed to the Mn acts as a hard dopant in the NBT–KBT lattice, creating oxygen vacancies and pinning the residual domains.     

Deviation from Stoichiometry in Cr2O3 at High Oxygen Partial Pressures

The deviation from stoichiometry, δ, in Cr₂−δO₃ was measured by a tensivolumetric method in the high pO₂ range of ≊10⁴ to 10⁴ Pa at 1100°C. The value of δ, or chromium vacancy concentration, was≊9×10⁻⁵ mol/mol Cr₂O₃ in air for Cr₂O₃ with 99.999% purity. The chemical diffusion coefficient, DT, determined from equilibration data was ≊4.6× cm²·s⁻¹ at 1100°C for pO₂= 2.2 ×10¹ Pa. The self-diffusion coefficient of Cr ions was calculated from and δ and found to be≊1.6×10-17 cm²-s⁻¹, in good agreement with recently measured values.     

Effects of V Substitution on Dielectric and Polarization Properties for Sr0.5Bi2.25Na1.25(Nb3−xVx)O12 Ceramics

The effects of V substitution for Nb on the dielectric and polarization properties of Sr_0.5Bi_2.25Na_1.25(Nb_{3− x} V _x )O₁₂ ceramics were investigated in this study. From the X-ray powder diffraction results, no secondary phase was detected in the composition range of 0–0.075. The remanent polarizations ( P _r) of the samples in the composition range of 0–0.03 were improved by the V substitution for Nb and the highest P _r value of approximately 15 μC/cm² was obtained at x =0.03; it was noted that the V substitution for Nb was effective in improving the P _r values in this ceramics. On the other hand, the coercive fields ( E _c) of the samples were on the order of approximately 40 kV/cm in such a composition range. Moreover, the anomalous variations in the dielectric constant were observed in the composition range of 0–0.075. Also, it was observed that the dielectric loss increased drastically at the temperature of approximately 500°C.