Effect of B2O3 and CuO on the sintering temperature and microwave dielectric properties of the BaTi4O9 ceramics

The effect of B₂O₃ and CuO on the sintering temperature and microwave dielectric properties of BaTi₄O₉ ceramics was investigated. The BaTi₄O₉ ceramics were able to be sintered at 975^∘C when B₂O₃ was added. This decrease in the sintering temperature of the BaTi₄O₉ ceramics upon the addition of B₂O₃ is attributed to the formation of BaB₂O₄ second phase whose melting temperature is around 900^∘C. The B₂O₃ added BaTi₄O₉ ceramics alone were not sintered below 975^∘C, but were sintered at 875^∘C when CuO was added. The formation of BaCu(B₂O₅) second phase could be responsible for the decrease in the sintering temperature of the CuO and B₂O₃ added BaTi₄O₉ ceramics. The BaTi₄O₉ ceramics containing 2.0 mol% B₂O₃ and 5.0 mol% CuO sintered at 900^∘C for 2 h have good microwave dielectric properties of ε_r = 36.3, Q× f = 30,500 GHz and τ_f = 28.1 ppm/^∘C     

Hydrothermal growth of BaTiO3 thin films on printed circuit boards for integral capacitor applications

Polycrystalline BaTiO₃ films were hydrothermally grown on Ti-coated substrates from 80^∘C to 200^∘C. Films grown at 200^∘C exhibited the lowest dielectric loss of around 0.1. Proton incorporation was more severe for the 80^∘C film resulting in higher dielectric losses and leakage currents about two orders of magnitude higher. Post deposition oxygen plasma treatment removed incorporated protons and reduced the loss tangent but did not reduce defect density. As such, the leakage current of the 80^∘C film remained high. The films had dielectric constants of 275 to 675 from 100 Hz to 100 kHz and a value of 67 from 100 MHz to 3 GHz.     

Dielectric properties of ZnNb2 O 6 -TiO 2 mixture thin films

ZnNb₂O₆-TiO₂ mixture thin films with multilayer structures were fabricated via a sol-gel spin coating process. TiO₂ layers were deposited on the pre-crystallized ZnNb₂O₆ layers in order to suppress the formation of the ixiolite phase which always forms in the bulk system. The phase constitution of the thin films, confirmed by X-ray diffraction (XRD), could be controlled by the annealing temperatures, which, in turn, influenced the dielectric properties of the thin films. TiO₂ layers crystallized as the anatase phase and then transformed to the rutile phase at temperatures higher than 725^∘C. Dielectric constants of the mixture thin films, measured at 1 MHz with an MIM (metal-insulator-metal) structure, increased from 27 to 41 with dielectric losses below 0.005 as the annealing temperature increased from 700^∘C to 900^∘C. The increase in the dielectric constants was understood to originate from the increasing amounts of the rutile phase. Temperature coefficients of capacitance (TCC) were also measured between 25^∘C and 125^∘C, which showed a decreasing manner from positive values to negative values with increasing annealing temperatures. When annealed at 850^∘C, the TCC of the thin films could be tuned to be approximately 0 ppm/^oC with dielectric constant and dielectric loss of 36 and 0.002, respectively.     

Low Temperature Sintering of BaTi<Subscript>4</Subscript>O<Subscript>9</Subscript>-Based Middle-<Emphasis Type="Italic">k</Emphasis> Dielectric Composition for LTCC Applications

Effect of glass addition on the low-temperature sintering and microwave dielectric properties of BaTi₄O₉-based ceramics were studied to develop the middle-k dielectric composition for the functional substrate of low-temperature co-fired ceramics. When 10 wt% of glass was added, sufficient densification was obtained and the relative density more than 98% was reached at the sintering temperature of 875C. The microwave dielectric properties were k = 32, Q × f = 9000 GHz, and t_cf = 10 ppm/C. As the added amount of glass frit with base dielectric composition, phase changes from BaTi₄O₉ to BaTi₅O₁₁ and Ba₄Ti₁₃O₃₀ was observed, which result in the modification of microwave dielectric properties.     

Characteristics of Bi4Ti3O12 thin films on ITO/glass and Pt/Si substrates prepared by R.F. sputtering and rapid thermal annealing

Bi₄Ti₃O₁₂ thin films are deposited on ITO/glass and Pt/Ti/Si(100) substrates by R.F. magnetron sputtering at room temperature. The films are then heated by a rapid thermal annealing (RTA) process conducted in oxygen atmosphere at temperatures ranging from 550–700^∘C. X-ray diffraction examination reveals that the crystalinity of the films grown on Pt/Ti/Si is better than that of the films grown on ITO/glass under the same fabrication conditions. SEM observation shows that the films grown on Pt/Ti/Si are denser than those grown on ITO/glass substrates. Interactive diffusion between the Bi₄Ti₃O₁₂ film and the ITO film increases with the increase of annealing temperature. The optical transmittance of the thin film annealed at 650^∘C is found to be almost 100% when the effect of the ITO film is excluded. The relative dielectric constants, leakage currents and polarization characteristics of the two films are compared and discussed.     

Electrical properties of Ga2O3-based dielectric thin films prepared by plasma enhanced atomic layer deposition (PEALD)

Ga₂O₃ and Ga₂O₃-TiO₂ (GTO) nano-mixed thin films were prepared by plasma enhanced atomic layer deposition with an alternating supply of reactant sources, [(CH₃)₂GaNH₂]₃, Ti(N(CH₃)₂)₄ and oxygen plasma. The uniform and smooth Ga₂O₃ and GTO thin films were successfully deposited. Excellent step coverage of these films was obtained by chemisorbed chemical reactions with oxygen plasma on the surface. The dielectric constant of GTO thin film definitely increased compared to Ga₂O₃ film, and the leakage currents of GTO films were comparable to Ga₂O₃ films. The leakage current density of a 40-nm-GTO film annealed at 600^∘C was approximately 1×10⁻⁷ A/cm² up to about 600 kV/cm.     

Scaling Effect on the Dielectric Constant in Ba(Ti x Zr1−x )O3 Thin Films

Recent work on PZT and BST thin films reveal a thickness dependence of the dielectric constant for a film thickness below 100 nm. This effect is commonly attributed to an interfacial layer between the electrode and the dielectric film (dead layer). In this contribution we report on the influence of the film thickness on the dielectric constant of Ba(Ti_xZr_{1 – x})O₃ thin films with different Zr-contents (x = 0–30 at.%). The films were prepared by chemical solution deposition (CSD) with thickness between 30 and 350 nm.The electrical characterization was performed in a temperature range between 25 and 200C. Results were interpreted with respect to the formation of a serial dead layer capacitance.     

Calculation of the intrinsic dead layers thicknesses from Au/Ba0.5Sr0.5TiO3/Pt thin film capacitors

Ferroelectric Ba_0.5Sr_0.5TiO₃ (BST) films were prepared on Pt/Ti/SiO₂/Si substrates by the sol-gel process. The films were spin-coated at 2000 rpm for 30 secs and then pyrolysed for 5 mins at the temperature of 350^∘C. This coating procedure was repeated for 3, 4, 5 and 6 times to obtain BST films with different thicknesses. After coating the films with the desired repetition times, the films were finally annealed in a conventional furnace at temperatures ranging from 600^∘C to 800^∘C with a 50^∘C interval in between. The films obtained with an annealing procedure of 750^∘C were polycrystalline with the presence of an impurity BaCO₃ phase. The capacitance and leakage current were measured and used to extract information on the metal-BST interface. With the series capacitance model and modified Schottky emission equation, the thickness of the dead layers for Au/BST and Pt/BST interfaces were calculated to be less than 6 nm and 5 nm, respectively.     

Low temperature sintering and microwave dielectric properties of Ba3Ti5Nb6O28 with B2O3 and CuO additions

The low sintering temperature and the good dielectric properties such as high dielectric constant (ε _r ), high quality factor (Q × f), and small temperature coefficient of resonant frequency (TCF) are required for the application of chip passive components in wireless communication low temperature co-fired ceramics (LTCC). In the present study, the sintering behaviors and dielectric properties of Ba₃Ti₅Nb₆O₂₈ ceramics were investigated as a function of B₂O₃-CuO content. The pure Ba₃Ti₅Nb₆O₂₈ system showed a high sintering temperature (1250^∘C) and had the good microwave dielectric properties: Q × f of 10,600 GHz, ε _r of 37, TCF of −12 ppm/^∘C. The addition of B₂O₃-CuO was revealed to lower the sintering temperature of Ba₃Ti₅Nb₆O₂₈, 900^∘C and to enhance the microwave dielectric properties: Q × f of 32,500 GHz, ε _r of 40, TCF of 9 ppm/^∘C. From the X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction (XRD) studies, these phenomena were explained in terms of the reduction of oxygen vacancies and the formation of secondary phases having the good microwave dielectric properties.     

ZnGa2O4 thin films fabricated by Sol-gel spinning coating process

ZnGa₂O₄ thin film phosphors have been synthesized on ITO coated glass and soda-lime glass at a firing temperature of 500^∘C and an annealing temperature of 500^∘C and 600^∘C via a chemical solution method using Zinc acetate dihydrate, Gallium nitrate hydrate and 2-methoxiethanol as a solution. XRD patterns of the film phosphors synthesized showed the peaks of ZnGa₂O₄ crystalline phases. AFM surface morphologies of the ZnGa₂O₄ thin film phosphors revealed marked differences according to an annealing temperature of 500^∘C and 600^∘C under an annealing atmosphere (3% H₂/Ar). On the other hand, the sheet resistance of ZnGa₂O₄ thin film phosphors, which were measured by four-point probe instrument, was approximately 5.76 Ω /square and 7.86 Ω /square with annealing temperature, respectively. The ZnGa₂O₄ thin film phosphors exhibited blue emission spectra with peak wavelength of 434 nm and 436 nm by ultra-violet excitation around 230 nm.     

Synthesis and properties of ferroelectric Si-doped (Bi, Nd)4Ti3O12 thin films by chemical solution deposition

Ferroelectric Si-doped (Bi,Nd)₄Ti₃O₁₂ thin films have been prepared on Pt/TiO_x/SiO₂/Si substrates through metal-organic compounds by the chemical solution deposition. The Bi_3.25Nd_0.75Ti_2.9Si_0.1O₁₂ (BNTS) precursor films were found to crystallize into the Bi-layered perovskite Bi₄Ti₃O₁₂ single-phase above 600^∘C. The synthesized BNTS films revealed a random orientation having a strong 117 reflection. The BNTS thin films prepared between 600^∘C and 700^∘C showed well-saturated P-E hysteresis loops with P _r of 13–14 μ C/cm² and E _c of 100–110 kV/cm at an applied voltage of 5 V. The surface roughness of the BNTS thin films was improved by Si doping compared with that of undoped Bi_3.35Nd_0.75Ti₃O₁₂ films.     

Characterization of Ba(Zr0.05 Ti0.95)O3 thin film prepared by sol-gel process

Ba(Zr_0.05Ti_0.95)O₃ (BZT) thin film (∼330 nm) was grown on Pt/Ti/SiO₂/Si(100) substrate by a simple sol-gel process. The microstructure and the surface morphology of BZT thin film were studied by X-ray diffraction and atomic force microscopy. The optical properties of BZT thin film were obtained by spectroscopic ellipsometry. The optical bandgap was found to be 3.74 eV of direct-transition type. Ferroelectric and dielectric properties of BZT thin film were also discussed. The electrical measurements were conducted on BZT films in metal-ferroelectric-metal (MFM) capacitor configuration. The results showed the film exhibited good ferroelectrity with remanent polarization and coercive electric field of 3.54 μC/cm² and 95.5 kV/cm, respectively. At 10 kHz, the dielectric constant and dielectric loss of the film are 201 and 0.029, respectively.     

Optical Properties of LiTaO3 Thin films crystallized by RTA processes

High-performance pyroelectric infrared detectors have been fabricated using Lithium tantalite (LiTaO₃) thin films deposited on Pt(111)/Ti/SiO₂/Si(100) substrates by diol-based sol-gel method and rapid thermal annealing (RTA) technique. The dielectric and pyroelectric properties of IR detectors of LiTaO₃ thin films crystallized by conventional and RTA processes are investigated. Experimental results reveal that the heating rate will influence strongly on dielectricity and pyroelectricity of LiTaO₃ thin films. The voltage responsivities (Rv) measured at 80 Hz increase from 5496 to 8455 V/W and the specific detecivities (D^∗) measured at 300 Hz increase from 1.94 × 10⁸ to 2.38 × 10⁸ cmHz^1/2/W with an increase of heating rate from 600 to 1800^∘C/min. However, the voltage responsivity and the specific detecivity decrease with heating rate in excess of 1800^∘C/min. The results show that the LiTaO₃ thin film detector with a heating rate of 1800^∘C/min exists both the maximums of voltage responsivity and specific detecivity.     

Thermal and dielectric properties of ZnO-B2O3-MO3glasses (M = W, Mo)

Glasses in the ZnO-B₂O₃-MO₃(M = W, Mo) ternary were examined as potential replacements to PbO-B₂O₃-SiO₂-ZnO glass frits with the low firing temperature (500–600^∘C) for the dielectric layer of a plasma display panels (PDPs). Glasses were melted in air at 950–1150^∘C in a narrow region of the ternary using standard reagent grade materials. The glasses were evaluated for glass transition temperature (T _g ), softening temperature (T _d ), the coefficient of thermal expansion (CTE), dielectric constant (ε _r ), and optical property. The glass transition temperature of the glasses varied between 470 and 560^∘C. The coefficient of thermal expansion and the dielectric constant of the glasses were in the range of 5–8 × 10^{− 6}/^∘C and 8–10, respectively. The addition of MO₃to ZnO-B₂O₃binary could induce the expansion of glass forming region, the reduction of T _g and the increase in the CTE and the dielectric constant of the glasses. Also, the effect of the addition of MO₃to ZnO-B₂O₃binary on the transmittance in the visible-light region (350–700 nm) was investigated.     

Crystallinity and photocatalytic activity of liquid phase deposited TiO2 films

Anatase TiO₂ films were deposited on glass substrates at 50 and 200^∘C to investigate the effect of growth temperature on the photocatalytic acitivity of the films. It was observed that the films grown at 200^∘C were composed of columnar crystallites and were more porous than the films grown at 50^∘C which had more compact structures. Also, the film crystallinity increased from 75 to 90% if the higher growth temperature was used. Despite the higher crystallinity, it was observed that for crystallinities between 60 and 90%, the photocatalytic behavior of the films was more significantly affected by changes in the surface area.     

Dielectric behavior of Bi2/3Cu3Ti4O12 ceramic and thick films

The paper reports on synthesis, sintering and microstructure of Bi_2/3Cu₃Ti₄O₁₂, a lead-free, high-permittivity material with internal barrier layer capacitor behavior. Complex impedance and capacitance of the ceramic and thick films were studied as a function of frequency (10 Hz–2 MHz) and temperature (−170 to 400°C). Dc electrical conductivity of the samples was measured in the temperature range 20–400°C. Broad and high maxima of dielectric permittivity versus temperature plots were observed reaching 60,000 for ceramic and 5,000 for thick films. The maxima decrease and shift to higher temperatures with increasing frequency. Two arcs ascribed to grains and grain boundaries were found in the plots of imaginary part versus real part of impedance. Analysis of the impedance spectra indicates that Bi_2/3Cu₃Ti₄O₁₂ ceramic could be regarded as electrically heterogeneous system composed of semiconducting grains and less conducting grain boundaries. The developed thick film capacitors with dielectric layers based on Bi_2/3Cu₃Ti₄O₁₂ exhibit dense microstructure, good cooperation with Ag electrodes, high permittivity up to 5,000 and relatively low temperature coefficient of capacitance in the temperature range 100–300°C. Broad maxima in the dielectric permittivity versus temperature curves may be attributed to Maxwell–Wagner relaxation.     

Micro-structure and ferroelectric properties of BiFeO3 thin films formed on Pt-coated r-plane sapphire substrates

Magnetoelectric BiFeO₃ (BFO) materials exhibit ferroelectric and ferromagnetic properties simultaneously, therefore they have a potential to be applied in magnetic as well as ferroelectric devices. BFO thin films were formed by depositing sol-gel solutions on Pt-coated r-plane sapphire dielectric substrates. We did not observe any secondary phase such as Bi₂Fe₄O₉ on the r-plane sapphire substrates, which is generally observed on Si substrates. We observed small ferroelectric grains of about 0.1 μm on Pt/sapphire structures. The leakage current density in BFO films was found to be decreased dramatically after optimizing process conditions of stoichiometric BFO chemical solution. The leakage current densities were in the range of 10^{− 7} A/cm² at room temperature and 10^{− 9} A/cm² at 80 K under 0.4 MV/cm applied electric field. The main reason for low leakage current is considered to be reduction of oxygen vacancies due to the presence of exclusive Fe^{3 +} valance state in the films. An applied electric field higher than 0.5 MV/cm was required to pole the BFO films, which made it difficult to obtain the saturated polarization at room temperature. We could measure the saturated remanent polarization in the BFO films at 80 K and the obtained remanent polarization was 100 μC/cm².     

Ferroelectric Properties of Bi3.25Nd0.75Ti3O12 Thin Films Prepared by MOD Process

Ferroelectric Bi_{4 – x}Nd_xTi₃O₁₂(BNdT) thin films with the composition (x = 0.75) were prepared on Pt/Ti/SiO₂/Si(100) substrate by metal-organic deposition. The films were annealed by various temperatures from 550 to 650C and then the electrical and structural characteristics were investigated for the application of FRAM. Electrical properties such as dielectric constant, 2Pr and capacitance were quite dependent on the thermal heat treatment. The measured 2Pr value on the BNdT capacitor annealed at 650C was 56 C/cm² at an applied voltage of 5 V. No fatigue was observed up to 8 × 10¹⁰ read/write switching cycles at a frequency of 1 MHz regardless of annealing temperatures.     

Nanocomposite ceramics based on La-doped BaTi2O5 and BaTiO3 with high temperature-independent permittivity and low dielectric loss

Nanocomposite ceramics containing a mixture of two ferroelectric phases, La-doped BaTi₂O₅ and BaTiO₃, with carefully-controlled phase amounts and ceramic microstructure have temperature-independent permittivity and low dielectric loss over very wide temperature ranges: ɛ = 95 ± 10 from 25 to 600 °C; tan δ = 0.02(2) from 25 to 400 °C, measured at 100 kHz. Further optimisation of properties should be possible.     

Fabrication of Er3+/Pr3+ Co-doped soda-lime glass thin films using RF magnetron sputtering method and optical property characterization

Er^3+/Pr³⁺ co-doped soda-lime glass thin films have been fabricated using RF magnetron sputtering method and their structural and optical properties have been studied. Deposition rate, crystallinity, and composition of glass thin films were investigated by scanning electron microscopy, transmission electron microscopy, and electron probe micro area analysis. Refractive index, birefringence and binding characteristics have been investigated using a prism coupler and X-ray photoelectron spectroscopy. Er³⁺/Pr³⁺ co-doped soda lime glass thin films were prepared by changing substrate temperature (room temp. ∼550^∘C), RF power (90 W–130 W), and Ar/O₂ gas flow ratio at processing pressure of 4 mTorr. Glass thin films could be obtained at the optimized processing condition at 350^∘C, RF power of 130 W, and gas flow of Ar:O₂ = 40:0 with maximum deposition rate of 1.6 μm/h. Refractive index and birefringence increased from 1.5614 to 1.5838 and from 0.000154 to 0.000552, respectively, as the content of Pr³⁺ increased. Binding energy of Pr3d also increased as the content of Pr³⁺ increased.