Leakage current characteristics of Bi3.15Nd0.85Ti3 − xZrxO12 thin films

Thin films of Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) and Bi_3.15Nd_0.85Ti_3 − xZr_xO₁₂ (BNTZ_x, x = 0.1 and 0.2) were fabricated on Pt/TiO₂/SiO₂/Si(100) substrates by a chemical solution deposition (CSD) technique at 700 °C. Structures, surface morphologies, leakage current characteristics and Curie temperature of the films were studied as a function of Zr ion content by X-ray diffraction, atomic force microscopy, ferroelectric test system and thermal analysis, respectively. Experimental results indicate that Zr ion substitution in the BNT film markedly decreases the leakage current of the film, while almost not changing the Curie temperature of the film, which is at about 420-460 °C. The decrease of the leakage current in BNTZ_x films is that the conduction by the electron hopping between Ti⁴⁺ and Ti³⁺ ions is depressed because Zr⁴⁺ ions can block the path between two adjacent Ti ions and enlarge hopping distance.     

Dielectric, electrical and magnetoelectric characterization of (x)Ni0.8Zn0.2Fe2O4 + (1 − x)Pb0.93La0.07(Zr0.60Ti0.40)O3 composites

The structural, electrical, dielectric, magnetic and magnetoelectric properties of (x)Ni_0.8Zn_0.2Fe₂O₄ + (1 − x)Pb_0.93La_0.07(Zr_0.60Ti_0.40)O₃ (x = 0, 0.15, 0.30, 0.45 and 1) have been studied by means of various experimental techniques. Polycrystalline samples of this series have been prepared by the double sintering ceramic method. X-ray diffraction data analysis revealed purity of the composites. Microstructural analysis using scanning electron microscopy mode depicts the presence of two phases in contact with each other. Dielectric properties were studied at and well above room temperature. Temperature dependent variation of the dielectric constant show diffused phase transition which can be well described by fitting the Lorentz-type relation, . Observation of well-saturated ferroelectric hysteresis loop and magnetic hysteresis loop for composites indicates that ferroelectric and magnetic ordering exist simultaneously at room temperature. The static value of magneto electric voltage coefficient (α_E) has been studied as a function of magnetic field at room temperature for all the composites. The maximum value of α_E is 7.53 mV/(cm Oe) for 85% PLZT-15% NZFO composites.     

Dielectric properties of Ba(Ti1 − xZrx)O3 solid solutions

This paper reports the structural and dielectric properties of Ba(Ti_1 − xZr_x)O₃ (x = 0-0.3) ceramics. Single-phase solid solutions of the samples were determined by X-ray diffraction. Microscopic observation by scanning electron microscope revealed dense, single-phase microstructure with large grains (20-60 μm). The evolution of dielectric behavior from a sharp ferroelectric peak (for x ≤ 0.08) to a round dielectric peak (for 0.15 ≤ x ≤ 0.25) with pinched phase transitions and successively to a ferroelectric relaxor (for x = 0.3) was observed with increasing Zr concentration. Compared with pure BaTiO₃, broaden dielectric peaks with high dielectric constant of 25,000-40,000 and reasonably low loss (tanδ: 0.01-0.06) in the Ba(Ti_1 − xZr_x)O₃ ceramics have been observed, indicating great application potential as a dielectric material.     

Microwave dielectric properties of Ba2 − xSrxLa3Ti3NbO15 ceramics

High dielectric constant and low loss ceramics in the system Ba_2 − xSr_xLa₃Ti₃NbO₁₅ (x = 0-1) have been prepared by conventional solid-state ceramic route. Ba_2 − xSr_xLa₃Ti₃NbO₁₅ solid solutions adopted A₅B₄O₁₅ cation-deficient hexagonal perovskite structure for all compositions. The materials were characterized at microwave frequencies. They show a linear variation of dielectric properties with the value of x. Their dielectric constant varies from 48.34 to 43.03, quality factor Q_u × f from 20,291 to 39,088 GHz and temperature variation of resonant frequency from 8 to 1.39 ppm/°C as the value of x increases. These low loss ceramics might be used for dielectric resonator (DR) applications.     

Electrical properties of Pb0.97La0.02(Zr0.95Ti0.05)O3 antiferroelectric thin films on TiO2 buffer layer

Pb_0.97La_0.02(Zr_0.95Ti_0.05)O₃ antiferroelectric thin films with thickness of 500 nm were successfully deposited on TiO₂ buffered Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) and Pt(1 1 1)/Ti/SiO₂/Si(1 0 0) substrates via sol-gel process. Microstructure of Pb_0.97La_0.02(Zr_0.95Ti_0.05)O₃ thin films was studied by X-ray diffraction analyses. The antiferroelectric nature of the Pb_0.97La_0.02(Zr_0.95Ti_0.05)O₃ thin films was confirmed by the double hysteresis behaviors of polarization and double buffer fly response of dielectric constant versus applied voltage at room temperature. The capacitance-voltage behaviors of the Pb_0.97La_0.02(Zr_0.95Ti_0.05)O₃ films with and without TiO₂ buffer layer were studied, as a function of temperature. The temperature dependence of dielectric constant displayed a similar behavior and the Curie temperature (T_c) was 193 °C for films on both substrates. The current caused by the polarization and depolarization of polar in the Pb_0.97La_0.02(Zr_0.95Ti_0.05)O₃ films was detected by current density-electric field measurement.     

Composition dependent preferential orientation, dielectric and ferroelectric properties of Pb(ZrxTi1 − x)O3 thin films derived by sol-gel process

Pb(Zr_xTi_1 − x)O₃ (x = 0.35, 0.40, 0.60, 0.65) thin films were prepared by sol-gel spin on technique. From the X-ray diffraction analysis, PZT films with Zr-rich compositions (x = 0.60 and 0.65) had (111) preferential orientation and the preferential orientation changed to (100) for Ti-rich compositions (x = 0.35 and 0.40). The dielectric measurements on the above compositions at room temperature showed that the dielectric constant values were higher in Zr-rich compositions compared to Ti-rich compositions. The ferroelectric behavior measured in terms of the remnant polarization (P_r) and coercive field (E_c) up to an applied field of 260 kV/cm depicted that the Zr-rich PZT films with (111) preferential orientation had higher P_r and lower E_c values compared to the Ti-rich PZT films with (100) preferential orientation can be understood from the domain switching mechanism.     

BaxSr1 − xTi1.02O3 metal-insulator-metal capacitors on planarized alumina substrates

Nanocrystalline barium strontium titanate (Ba_xSr_1 − xTi_1.02O₃) thin films with a barium content of x = 0.8, 0.9 and 1 have been fabricated in a metal-insulator-metal configuration on glass-planarized alumina substrates. Cost-effective processing measures have been utilized by using poly-crystalline alumina substrates, wet-chemical processing of the dielectric, and by a small physical area of the ferroelectric capacitors (as low as 50 µm² for radio frequencies measurements). Glass-planarization on alumina ceramic substrates enables barium strontium titanate films with high quality and homogeneity. We mainly focus on fine-tuning the electrical performance in the low gigahertz range (< 10 GHz). Extensive micro-structural and electrical characterization has been performed. Micro-structural information is obtained by: Transmission Electron Microscopy, Scanning Electron Microscopy and X-ray diffraction. The dielectric response is investigated as a function of temperature, frequency and electric field for each sample. We measured a relatively constant permittivity for typical operating temperatures of applications. The quality factor Q is between 21 and 27 at 1 GHz at zero DC bias and the tuning ratio η between 1.8 and 2.2 at |E| = 0.4 MV/cm.     

Nanograins dependent dielectric constant, tunability, phase transition, impedance spectroscopy and leakage current of (Pb1 − xSrx)TiO3 thin films

Nanostructured (Pb_1 − xSr_x)TiO₃ (PST) (x = 0.1, 0.2 and 0.3) thin films have been prepared by chemical solution deposition process using spin coating technique. The solution as such was deposited on Pt/Ti/SiO₂/Si substrates and annealed at 650 °C/3h. Nanograins dependent dielectric properties of PST films show dielectric constant up to the higher frequency region, low losses, large tunability and phase transition at small temperature. The impedance data has been fitted by Cole-Cole model to study the effect of grain boundaries on the dielectric properties. The current-voltage characteristics have been measured to study leakage current in PST films and described by Poole-Frenkel emission model. It is suggested that the key carrier transport process in PST films is emission of electrons from a trap state near the metal-film interface into a continuum of states associated with each conductive dislocation. The activation energy value for carrier transport in PST films is obtained from temperature-dependent current-voltage characteristics.     

Microstructure and electrical properties of Ba0.7Sr0.3(Ti1 − xZrx)O3 thin films prepared on copper foils with sol-gel method

Ba_0.7Sr_0.3(Ti_1 − xZr_x)O₃ (x = 0, 0.1, 0.2) (BSZT) thin films have been prepared on copper foils using sol-gel method. The films were annealed in an atmosphere with low oxygen pressure so that the substrate oxidation was avoided and the formation of the perovskite phase was allowed. The X-ray diffraction results show a stable polycrystalline perovskite phase, with the diffraction peaks of the BSZT films shifting toward the smaller 2θ with increasing Zr content. Scanning electron microscopy images show that the grain size of the BSZT thin films decreases with increasing Zr content. High resolution transmission electron microscopy shows the clear lattice and domain structure in the film. The dielectric peaks of the BSZT thin films broaden with increasing Zr content. Leakage current density of Ba_0.7Sr_0.3(Ti_1 − xZr_x)O₃ (x = 0.1) thin film is the lowest over the whole applied voltage.     

Structure, dielectric, ferroelectric, and optical properties of (1 − x)Ba(Zr0.2Ti0.8)O3 − x(Ba0.7Ca0.3)TiO3 thin films prepared by sol-gel method

We report high dielectric tunabilities of (1 − x)Ba(Zr_0.2Ti_0.8)O₃ − x(Ba_0.7Ca_0.3)TiO₃ (BZT-xBCT) (x = 0.15, 0.30, 0.40, 0.45, 0.50, and 0.55) thin films prepared by a sol-gel method. The films show a pure perovskite structure with random orientation. They have moderate dielectric constant ranging from 350 to 500 and low dielectric loss near 3.0% at 1 kHz with 0 V bias at room temperature. The dielectric tunability of the BZT-0.55BCT thin films is up to 65% at 400 kV/cm and 100 kHz. The films exhibit a high optical transmission in the range of 420 nm-1500 nm. Their optical band gap energies are about 3.90 eV.     

Preparation and characterization of highly (1 1 1)-oriented (Pb,La)(Zr,Ti)O3 thin films by sol-gel processing

Lanthanum modified lead zirconate titanate (Pb_0.91La_0.09)(Zr_0.65Ti_0.35)O₃ (PLZT) ferroelectric thin films were grown on Pt/Ti/SiO₂/Si(1 0 0) and fused quartz substrates using a sol-gel method with rapid thermal annealing processing. The results showed that the highly (1 1 1)-oriented pervoskite PLZT thin film growth on Pt/Ti/SiO₂/Si(1 0 0) substrates. The electrical measurements were conducted on PLZT films in metal-ferroelectric-metal capacitor configuration. The PLZT thin films annealed at 600 °C showed well-saturated hysteresis loops with remanent polarization and coercive electric field values were 10.3 μC/cm² and 36 kV/cm, respectively, at an applied field of 300 kV/cm. At 100 kHz, the dielectric constant and dielectric loss of the film are 682 and 0.021, respectively. The PLZT thin film on fused quartz substrate, annealed at 600 °C, exhibited good optical transmittance, the band gap of optical direct transitions is 3.89 eV.     

Phase formation, microstructure, and dielectric properties of (1 − x)PZT-(x)PCN ceramics

Ceramics in a PZT-PCN system with the formula (1 − x)Pb(Zr_1/2Ti_1/2)O₃-(x)Pb(Co_1/3Nb_2/3)O₃, where x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, and 1.0, were prepared using a solid-state mixed-oxide technique with columbite−CoNb₂O₆ and wolframite−ZrTiO₄ precursors. The crystal structure of the specimens studied with X-ray diffraction (XRD) analysis showed a coexistence between tetragonal and pseudo cubic phases at composition x = 0.2. The SEM micrograph showed that the average grain size significantly decreased with increasing PCN content. A maximum dielectric constant was observed at composition x = 0.2, while the transition temperature strongly decreased with increasing PCN content. All ceramics also showed diffused phase transition behaviors with a minimum diffusivity at x = 0.2. The morphotropic phase boundary (MPB) lay at the 0.8PZT-0.2PCN composition.     

Properties of the PLZTN x/54/46 (0.4 ≤ x ≤ 1.4) ceramic system

Even though the PZT ceramic system has been thoroughly studied and modified with different additives, no numerous reports have been published focusing on the PZT double ‘soft’ modification with La³⁺ and Nb⁵⁺ (PLZTN). In this paper, we explore the structural, morphological, dielectric, ferroelectric and piezoelectric properties of the PLZTN system for different doping levels (x_La3+ = x_Nb5+ = 0.4, 0.6, 0.8, 1.0 and 1.4 at.%) synthesized by conventional powders reaction. The temperature dependence of the piezoelectric response of poled ceramic disks is also analyzed and, according to its overall features, an optimum modification is proposed in order to develop PZT-based sensors for several applications.     

Structure and thermal conductivity of Gd2(TixZr1 − x)2O7 ceramics

The Gd₂(Ti_xZr_1 − x)₂O₇ (x = 0, 0.25, 0.50, 0.75, 1.00) ceramics were synthesized by solid state reaction at 1650 °C for 10 h in air. The relative density and structure of Gd₂(Ti_xZr_1 − x)₂O₇ were analyzed by the Archimedes method and X-ray diffraction. The thermal diffusivity of Gd₂(Ti_xZr_1 − x)₂O₇ from room temperature to 1400 °C was measured by a laser-flash method. The Gd₂Zr₂O₇ has a defect fluorite-type structure; however, Gd₂(Ti_xZr_1 − x)₂O₇ (0.25 ≤ x ≤ 1.00) compositions exhibit an ordered pyrochlore-type structure. Gd₂Zr₂O₇ and Gd₂Ti₂O₇ are infinitely soluable. The thermal conductivity of Gd₂(Ti_xZr_1 − x)₂O₇ increases with increasing Ti content under identical temperature conditions. The thermal conductivity of Gd₂(Ti_xZr_1 − x)₂O₇ first decreases gradually with the increase of temperature below 1000 °C and then increases slightly above 1000 °C. The thermal conductivity of Gd₂(Ti_xZr_1 − x)₂O₇ is within the range of 1.33 to 2.86 W m^− 1 K^− 1 from room temperature to 1400 °C.     

Structural and microwave dielectric behavior of (Li1/4Nb3/4) substituted ZrxSnyTizO4 (x + y + z = 2) system

The phase structure, microwave dielectric properties, and their stability with different annealing conditions have been investigated in (Li_1/4Nb_3/4) substituted Zr_xSn_yTi_zO₄ system. The sintering temperature of Zr_xSn_yTi_zO₄ ceramic was lowered from 1500 to 1140 °C by (Li_1/4Nb_3/4) substitution. Both X-ray diffraction (XRD) analysis and electron diffraction (ED) analysis revealed that the (Li_1/4Nb_3/4) substituted Zr_xSn_yTi_zO₄ ceramic crystallized as the high-temperature disordered ZrTiO₄ phase. As the content of Sn increased from 0.10 to 0.30, the permittivity of the (Zr_1−xSn_x)(Li_1/4Nb_3/4)_0.4Ti_0.6O₄ ceramic decreased gradually from 35.5 to 31.5, the Q_f value increased from 37,800 to 58,300 GHz, and TCF value shifted slightly from −4.5 to −33.0 ppm °C⁻¹. Both the phase structure and microwave dielectric properties of (Zr_1−xSn_x)(Li_1/4Nb_3/4)_0.4Ti_0.6O₄ ceramics were stable with annealing conditions.     

Morphotropic phase boundary in high temperature ferroelectric xBi(Zn1/2Ti1/2)O3 − yPbZrO3 − zPbTiO3 perovskite ternary solid solution

A bismuth and lead oxide based perovskite ternary solid solution xBi(Zn_1/2Ti_1/2)O₃ − yPbZrO₃ − zPbTiO₃ (xBZT − yPZ − zPT) was investigated as an attempt to develop a high T_C ferroelectric material for piezoelectric sensor and actuator applications. A morphotropic phase boundary (MPB) between rhombohedral and tetragonal phases was determined through an XRD study on a pseudobinary line 0.1BZT − 0.9[xPT − (1 − x)PZ] for composition 0.1Bi(Zn_1/2Ti_1/2)O₃ − 0.5PbZrO₃ − 0.4PbTiO₃. Enhanced piezoelectric and ferroelectric activities were observed for MPB composition with dielectric constant ε_r′ ~ 23,000 at Curie temperature (T_C) ≈ 320 °C, remanent polarization (P_r) = 35 μC/cm², piezoelectric coefficient (d₃₃) = 300 pC/N, unipolar strain = 0.15%, and electromechanical coupling coefficient (k_P) = 0.45.     

Sintering behavior, microstructure and microwave dielectric properties of Li2+xTiO3 (0 ≤ x ≤ 0.2)

Sintering behavior, microstructure and microwave dielectric properties of Li_2+xTiO₃ (0 ≤ x ≤ 0.2) ceramics have been studied by X-ray diffraction (XRD), scan electron microscopy (SEM), Raman spectra, dilatometery and microwave resonant measurement in this research. Homogeneous non-stoichiometric composition with rock salt structure existed for Li_2+xTiO₃ (0 ≤ x ≤ 0.2) ceramics. The sintering temperature was successfully reduced and highly densified sample could be obtained with appropriate excessive amount of lithium (x = 0.08). A transient reactive liquid phase sintering mechanism was proposed. The preferred orientation of grain growth and micro-cracks existed in the Li₂TiO₃ (x = 0) sample disappeared in the lithium excessive samples with x ≥ 0.08. The microwave dielectric properties varied significantly with the excessive amount of lithium. Optimized microwave dielectric properties were obtained for the x = 0.08 composition: ?_r = 24.6, Q × f = 66,000 GHz, and τ_f = 22.1 ppm/°C.     

Synthesis, low-temperature sintering and the dielectric properties of the ZnO-(1 − x)TiO2-xSnO2 (x = 0.04-0.2)

ZnO-(1 − x)TiO₂-xSnO₂ (x = 0.04-0.2) ceramics were prepared by conventional mixed-oxide method combined with a chemical processing. Fine particle powders were prepared by chemical processing to activate the formation of compound and to improve the sinterability. One wt.% of V₂O₅ and B₂O₃ with the mole ratios of 3:1 were used to lower the sintering temperature of ceramics. The effect of Sn content on phase structure and dielectric properties were investigated. The results show that the substituting Sn for Ti accelerates the hexagonal phase transition to cubic phase, and an inverse spinel structure Zn₂(Ti_1−xSn_x)O₄ solid solution forms. The best dielectric properties obtained at x = 0.12. The ZnO-0.88TiO₂-0.12SnO₂ ceramics sintered at 900 °C exhibit a good dielectric property: ?_r = 29 and tan δ = 9.86 × 10⁻⁵. Due to their good dielectric properties, low firing characteristics, ZnO-(1 − x)TiO₂-xSnO₂ (x = 0.04-0.2) can serve as the promising microwave dielectric capacitor.     

Influence of strontium substitution on the dielectric properties of Ca(1 − x)SrxTi0.9Zr0.1O3 solid solutions

A conventional solid-state reaction has been used to synthesize the perovskite Ca_(1 − x)Sr_xTi_(1 − y)Zr_yO₃ (y = 0.1). The aim of this study is focused on the development of new materials with complex perovskite structure and on their dielectric property improvement. The temperature and substitutional ratio effects on the different phase evolutions is investigated by X-ray diffraction (XRD) and scanning electron microscope observations. These ceramics sintered at 1500 °C, present a density higher than 95% and their dielectric properties are significantly affected by the substitution. The CaTiO₃ ceramic present a relative permittivity of 190 and the temperature coefficient of the permittivity of − 1828 ppm/C°. The substitution with zirconium (for x = 0 and y = 0.1: Σ = 145; |Σ = − 917 ppm/C°). Both permittivity and temperature coefficient values decrease; however, an opposite effect is observed when substituting with the strontium. With increasing an x value and maintaining a y value constant (y = 0.1), the dielectric constant increases and the temperature coefficient remains constant. Therefore, the dielectric properties of CaTiO₃ ceramics are improved with the combined substitution.     

Synthesis of nanocrystalline xCuFe2O4-(1 − x)BiFeO3 magnetoelectric composite by chemical method

xCuFe₂O₄-(1 − x)BiFeO₃ spinel-perovskite nanocomposites with x = 0.1, 0.2, 0.3 and 0.4 were prepared using citrate precursor method. X-ray diffraction (XRD) analysis showed phase formation of xCuFe₂O₄-(1 − x)BiFeO₃ calcined at 500 °C. Transmission electron microscopy (TEM) shows formation of nanocrystallites of xCuFe₂O₄-(1 − x)BiFeO₃ with an average particle size of 40 nm. Variation of dielectric constant and dielectric loss with frequency showed dispersion in the low frequency range. Coercivity, saturation magnetization and squareness have been found to vary with concentration of ferrite phase and annealing temperature due to the increase in crystallite size. Squareness and coercivity increased with an increase in annealing temperature up to 500 °C and then decreased with a further increase in temperature to 600 °C. Magnetoelectric effect of the nanocomposites was found to be strongly depending on the magnetic bias and magnetic field frequency.