Mixed Oxide Method Research Articles

Dielectric and Electric Properties of Ba0.996La0.004Ti0.999O3 Ceramics Doped with Europium and Hafnium Ions.

Lanthanum-modified BaTiO3 electroceramic materials have superior dielectric and piezoelectric properties. Ba0.996La0.004Ti0.999O3 (BLT4) seems to be a serious candidate for ultracondensator applications. This manuscript describes the results of hafnium and europium modification of BLT 4 ceramics. The pure and doped ceramic materials were synthesized by the conventional mixed oxide method. The microstructure of obtained samples was examined by scanning electron microscope. The investigations reveal strong correlations between the presence of admixture and the grain size, which was especially visible in the case of the hafnium dopant. The frequency and temperature dielectric characteristics measurements revealed a decrease in electric permittivity. Moreover, the impedance spectroscopy investigations showed severe changes in grains and grain-boundary resistivity, which was connected with changes in electric conductivity.

Effect of Al2O3 nano-particles on Ba(Zr0.95Ti0.05)O3 ceramics prepared by mixed oxide method

In this study, the effect of Al2O3 nano-particles on Ba(Zr0.95Ti0.05)O3 or BZT ceramics prepared by mixed oxide method with various amount of Al2O3 were investigated. The BZT powders were calcined at 1100 °C for 3 h with heating rate of 5 °C/min. The sintering procedure of BZT + x wt.% Al2O3 nano-particles (x = 0.3, 0.7 and 1.0) was carried out at 1300 °C for 2 h with heating rate of 5 °C/min. The results showed that, all XRD patterns of BZT + x wt.% Al2O3 nano-particles ceramics could be matched with a JCPDS data file number 06-0399. The BZT + 0.7 wt.% Al2O3 nano-particles ceramic was showed the highest density about 5.9 g/cm3, Vickers micro-hardness was 8.9 GPa, dielectric constant was 2005 and dielectric loss was 0.01 at 1 kHz frequency.

Enhancement of electrostrictive and magnetic performance with high energy storage efficiency in Fe2O3 nanoparticles-modified Ba(Zr0.07Ti0.93)O3 multiferroic ceramics

Lead-free Ba(Zr0.07Ti0.93)O3/xFe2O3 (93BZT/xFe2O3, x = 0-1.0 mol%) ceramics were prepared using a conventional mixed oxide method. The Fe2O3 nanoparticles additive disturbed the long-range ferroelectric order of the ceramics by changing the normal P-E hysteresis loop for the unmodified ceramic into a constricted loop for the 0.5 mol % Fe2O3 ceramic thereby resulting in an enhancement of the electric field-induced strain and electrostrictive coefficient at this composition. The 1.0 mol% Fe2O3 ceramic showed the highest energy storage efficiency (98%). The M-H hysteresis loop and the magnetocapacitance value were improved by the Fe2O3 nanoparticles additive. Results indicated that the magnetic and electrical performances of Ba(Zr0.07Ti0.93)O3 modified by the Fe2O3 nanoparticle could be remarkably improved, thereby suggesting that this ceramic system has potentials for multifunction device applications.

Structural, dielectric and energy storage characteristics of (Pb1−xSrx)(Zr0.80Ti0.20)O3 antiferroelectric compositions

Antiferroelectric(AFE) and Relaxor ferroelectric(FE) ceramics are most popular for energy storage applications. In our work we have selected compositions near the FE-AFE phase boundary in the quaternary phase PbTiO3(PT)-PbZrO3(PZ)-SrTiO3(ST)-SrZrO3(SZ). Bulk ceramics based on the composition (Pb1−xSrx)(Zr0.80Ti0.20)O3 [PSZT] with 0.14 ≤ x ≤ 0.20 were synthesized by mixed oxide method. XRD and Raman studies were carried out to understand the structural modifications as a function of Sr2+ concentration. Structure refinement using Rietveld method revealed a change from rhombohedral(R3c) for x = 0,to a coexistence of rhombohedral(R3c) and tetragonal(P4mm) for x = 0.15,and tetragonal(P4mm) for x > 0.15. Polarization - Electric field measurements revealed a systematic FE to AFE transition on A-site Sr2+- substitution. Weibull distribution analysis for all PSZT ceramics was carried out to obtain the Breakdown dielectric strength (BDS). Recoverable energy density and energy storage efficiency were evaluated from the P-E hysteresis and have been correlated with their microstructure for their potential energy storage applications.

Effect of Sr2+doping on the phase transition of BaTiO3 lead-free ferroelectric ceramics

The single phase Ba1−xSrxTiO3 (x = 0, 0.4, 0.8) ceramic compositions were fabricated through solid state (mixed oxides) method calcined at 850 °C and sintered at 1200 °C in air. The XRD patterns revealed the single phase BaTiO3 composition with a space group of pm-3m. The shifting of the (1 0 0) XRD peak to higher 2θ values is accredited to the substitution of comparatively smaller ion of Sr2+ (1.4 Å) for larger Ba2+ (1.6 Å) ion following the Braggs diffraction law (2dsinθ = mλ). The phase transition or Curie point from polar ferroelectric phase to non-polar paraelectric phase of Ba1−xSrxTiO3 was reported to decrease with increasing Sr2+ content in Ba1−xSrxTiO3 compositions. The value of the dielectric constant decreased with increasing the content of Sr2+, which may be attributed to the substitution of comparatively smaller ion of Sr2+ for Ba2+ in the perovskite structured Ba1−xSrxTiO3.

Dielectric and optical spectroscopy of new polycrystalline ceramic for device applications

The polycrystalline double perovskite Li2GdFeTiO6 was synthesized through the solid-state mixed oxide method and its preliminary crystal structure was investigated by the XRD technique. The structure of the material was identified to be tetragonal with space group P4bm using POWD and MATCH software. The morphology of the sample was investigated through a scanning electron microscope (SEM) and the average grain size was found to be 3.82 μm using the intercept technique. The investigation of the perovskite phase and various vibrational modes were carried out through FTIR spectroscopic technique. The bandgap (Eg = 1.73 eV) and visible light sensitivity of the material were identified by UV–Visible spectroscopic operation carried in the range 200–700 nm. The dielectric and related properties were investigated as a function of frequency and temperature using an impedance analyzer (LCR meter). Room-temperature dielectric investigation suggests it may be useful for storage application. The transport activities investigated through conductivity, impedance, and modulus technique illustrate the significant influence of grains on transportation of charges.

The transition from dielectric-temperature stability to diffuse phase transition behavior induced by the sintering temperature for (Ba0.93La0.07)(Ti0.93Tb0.07)O3 ceramics

Nominal (Ba0.93La0.07)(Ti0.93Tb0.07)O3 ceramics (BLTT7) were prepared at different sintering temperatures of Ts = 1100–1400 °C using a mixed-oxide method. The electron paramagnetic resonance (EPR) of Tb4+ in BLTT7 acted as a probe to investigate the effect of Ts on the transition from dielectric-temperature stability to diffuse phase transition behavior. Three tetragonal BLTT7 ceramics sintered at Ts = 1100, 1200 and 1300 °C exhibited increasing dielectric-temperature stability, whereas the pseudocubic BLTT7 sintered at Ts = 1400 °C exhibited a diffuse phase transition behavior with higher permittivity and the temperature stability. A so-called core-shell structure should be responsible for the flattening of the Curie peak at Ts ≤ 1300 °C. The higher Ts (=1400 °C) led to a complete incorporation of La/Tb ions in the BaTiO3 lattice and the collapse of the core-shell structure. The transfer of Tb4+ from the shell at Ts ≤ 1300 °C to the perovskite lattice at Ts = 1400 °C was confirmed by EPR. The solid solution formation of BLTT7 sintered at different Ts is discussed.

Structure and microwave dielectric properties of NaSr4V5O17 ceramics for LTCC applications

A new microwave dielectric ceramic, NaSr4V5O17 with low firing temperature was fabricated via the traditional mixed oxide method. Rietveld refinement of XRD profiles and Raman spectrum analysis ascertained that the NaSr4V5O17 compounds crystallized into Sr2V2O7-like triclinic structure with space group P-1 (2) and Z = 1.6. The variation of Q × f value was explained by the combined effects of mean grain size and cell volume rather than packing fraction and bond valence. The change regulation of εr was similar to that of density. The |τf| value is mainly related to the cations bond valence. The NaSr4V5O17 ceramics sintered at 725 °C showed good compatibility with Ag electrode and superior dielectric properties: εr = 8.6, Q × f = 45 900 GHz, τf = −57.0 ppm/K, making it a potential application for LTCC.

Structural and impedance spectroscopy study of Mn1.5Y1.5CSr1.5Ba1.5 antiperovskite

The experimental study on temperature and frequency dependent impedance spectroscopy study of an antiperovskite is being reported for the first time in this work as until now only the theoretical studies on dielectric behavior of various antiperovskites have been reported. Additionally, the effect of the presence of alkaline earth metals at A-site on the physical properties of an antiperovskite has been investigated for the first time. The structural and impedance characteristics of Mn1.5Y1.5CSr1.5Ba1.5 antiperovskite, synthesized by mixed oxide method, have been reported in this work. X-Ray Diffraction (XRD) analysis of this antiperovskite indexes it in a cubic crystal system with Ia3‾ space group. The impedance spectroscopy study reveals that the persistent rise in the magnitude of relative dielectric constant (εr) and dielectric loss (tan δ), with increasing temperature, is due to thermally activated charge carriers which results in the surge in conductivity of the sample. The dielectric dispersion in this antiperovskite is ascribed to Maxwell–Wagner form of interfacial polarization that is explained on the basis of Koop's phenomenological theory. The complex impedance analysis signifies a non-Debye relaxation process for this compound.

Investigation of Bi0.5(Na0.80K0.20)0.5TiO3-LiNbO3-Ba(Ti0.90Sn0.10)O3 Lead-Free Piezoelectric Ceramics

The ceramics with the formula of (1-y)[0.995Bi0.5(Na0.80K0.20)0.5TiO3-0.005LiNbO3]-yBa(Ti0.90Sn0.10)O3 or (1-y)[0.995BNKT-0.005LN]-yBTS (y = 0-0.05 mol fraction) were successfully prepared by a conventional mixed oxide method. It was found that all compositions showed single phase with a mixed rhombohedral/tetragonal structure. The highest piezoelectric coefficient (d33 = 175 pC/N) with good dielectric (εr = 1775, tanδ = 0.0534) and ferroelectric properties (Pr = 12.33 µC/cm2, Rsq = 1.37) was obtained for y = 0.04 sample. The bipolar S-E loops showed highest Smax = 0.25% at y = 0.05.

Sequential uptake of cadmium and methylene blue from binary solution using zeolite‐TiO2 modified porous CaCu3Ti4O12 photocatalyst

AbstractThis work describes the synthesis of CaCu3Ti4O12 (CCTO) by a facile conventional oxide mixing method. The prepared CCTO particles were further modified with anatase TiO2 NPs (~55 nm size) and zeolite supported TiO2 nanoparticles (NPs) (~58 nm size) for the photocatalytic removal of MB and Cd2+ from the aqueous media under compact fluorescent light. Both nascent and modified CCTO composite materials were characterized using X‐ray diffraction, scanning electron micrograph /energy dispersion X‐ray, BET, UV–VIS‐DRS, and pH of the point of zero charge analyses. These composite materials revealed with remarkable affinity toward MB and Cd2+, whereby the maximum photocatalytic degradation and adsorption capacity reached to 73 and 77 mg/g, respectively. The cations removal efficiencies of the prepared composite materials were found increased in the binary solutions of MB and Cd2+ ions resulting in enhanced degradation and adsorption capacity, qe, up to 132, and 137 mg/g, respectively. The reusability tests revealed that the efficiencies of prepared composites gradually decreased upon reuse.

Effect of soaking times on ferroelectric properties and strain behavior of PLZT ceramics

In this work, PLZT x/65/35 powders where x=4, 6, 8 and 10 mol% were prepared by mixed-oxide method and sintered at 1200 °C for 4, 8 and 12h. The electric field induced strain (S-E) and electric field induced polarization (P-E) were measured by using strain and polarization measurement system. It was found that PLZT 6/65/35 had the optimized condition with the soaking time of 12h. The highest remnant polarization (18.24 μC/cm2), saturated polarization (24.73 μC/cm2), strain (0.4090%) and d* 33 (204.50 pm/V) It can be concluded that the soaking times affected to ferroelectric properties and strain behavior.

Dielectric Properties of Modified Lead Zirconate Titanate

In this paper, the dielectric properties of modified i. e. alkali doped lead zirconate titanate Pb(Zr1- xTix)O3 has been studied. The composition Pb1-x (La1-zDz)x (Zry Ti1-y)1-x/4 O3;where x = 0.10, y = 0.70, z = 0.0, 0.1, 0.2, and 0.3, D= Na, K and Li has been prepared by conventional mixed oxide method at a temperature of 11000C. Dielectric constant and dielectric loss measurement of the sintered pellets has been measured. Dielectric measurement shows that the dielectric constant decreases with an increase in temperature. The results show that the dielectric loss is very small and decreases with frequency above 300°C. The increase in the dielectric constant observed at high temperatures and low frequencies is explained in the paraelectric state.

Improvement in Electrical Properties of (Bi0.5Na0.5)TiO3 (BNT) Ceramics Using the Seed-Induced Method

(Bi0.5Na0.5)TiO3 (BNT) lead-free ceramics were prepared by the seed-induced technique using different particle sizes of BaTiO3 (BT) powder as seeds. The BT seeds was synthesized by the molten-salt method and then calcined at different temperatures of 750 (750BTs), 800 (800BTs) and 850 °C (850BTs). The pure perovskite seeds (5 mol%) were mixed with the starting materials of the BNT system for conventional mixed oxide method. After that, the mixture was calcined and sintered at 900 °C for 2 h and 1100 °C for 2 h, respectively. From results it was found that the particle size of BT seed increased with calcine temperature increase from 750 to 850 C. The samples of non-BT seed (S0) and BT seed-added (S1, S2 and S3) showed pure perovskite phase. Average density values were in the range of 5.53-5.77 g/cm3. Dielectric constant (εr) measured at room temperature (at 1 kHz) was in the range of 732.04-788.59. The dielectric loss (tanδ), remnant polarization (Pr) and coercive field (Ec) values decreased with the addition of BT seed. The highest piezoelectric coefficient (d33) ∼156 pC/N was obtained for the sample of 850BTs (S3).

Phase composition of ceramic samples of the BaTiO3–PbTiO3–BaZrO3 system near BaTiO3

Ceramics (1 − x) Ba(Ti1 – yZry)O3·xPbTiO3 with x = 0, y = 0; x = 0, y = 0.05; x = 0.05, y = 0.05; x = 0.10, y = 0.05; x = 0.15, y = 0.05; x = 0.20, y = 0.05 were obtained by solid-state mixed oxide method at 1400 °C. Phase composition of the ceramic samples was determined by the Rietveld method using powder diffraction data. At the first stage, the refinement was done for the two most representative sections of the registered XRD patterns, namely: 2θ = 44.6 °–46.2 ° and 2θ = 55.4 °–57.2 °. At the second stage, the refinement for the full XRD patterns was performed. The quantitative content of phases and their crystallographic data is determined. All samples contain a perovskite tetragonal phase (space group P4 mm). The cubic phase (space group Pm-3 m) is present in the samples with x = 0, y = 0; x = 0, y = 0.05; x = 0.05, y = 0.05; x = 0.10, y = 0.05. The orthorhombic phase (space group Amm2) is contained in the samples with x = 0, y = 0.05; x = 0.05, y = 0.05; x = 0.10, y = 0.05; x = 0.15, y = 0.05. Substitution of Ti for Zr in the tetragonal form of BaTiO3 reduces the tetragonal distortion of the unit cell. Substitution of Ba for Pb increases the tetragonal distortion of the unit cell.

Effect of Sb-site nonstoichiometry on the structure and microwave dielectric properties of Li3Mg2Sb1\u2212xO6 ceramics

The non-stoichiometric Li3Mg2Sb1−xO6 (0.05 ⩽ x ⩽ 0.125) compounds have been prepared via the mixed oxide method. The influences of Sb nonstoichiometry on the sintering behavior, microstructure, phase composition along with microwave dielectric performances for Li3Mg2Sb1−xO6 ceramics were studied. Combined with X-ray diffraction (XRD) and Raman spectra, it was confirmed that phase composition could not be affected by the Sb nonstoichiometry and almost pure phase Li3Mg2SbO6 was formed in all compositions. Appropriate Sb-deficiency in Li3Mg2SbO6 not only lowered its sintering temperature but also remarkably improved its Q×f value. In particular, non-stoichiometric Li3Mg2Sb0.9O6 ceramics sintered at 1250 °C/5 h owned seldom low dielectric constant εr = 10.8, near-zero resonant frequency temperature coefficient τf = −8.0 ppm/°C, and high quality factor Q×f = 86,300 GHz (at 10.4 GHz). This study provides an alternative approach to ameliorate its dielectric performances for Li3Mg2SbO6-based compounds through defect-engineering.

Na1/3Ca1/3Bi1/3Cu3Ti4O12/poly(vinylidene fluoride) composites with high dielectric permittivity and low dielectric loss

Polymer matrix composites of Na1/3Ca1/3Bi1/3Cu3Ti4O12/PVDF with various volume fractions of filler were fabricated. Na1/3Ca1/3Bi1/3Cu3Ti4O12 powders synthesized using a conventional mixed–oxide method were used to incorporate in a PVDF polymer for increasing the dielectric permittivity (ε′). The phase formation and morphologies of the composites were characterized. Na1/3Ca1/3Bi1/3Cu3Ti4O12 particles were found randomly distributed and quite good dispersed in the PVDF polymer. The polar β– and γ–PVDF phases as well as the nonpolar α–PVDF phase were confirmed to exist in the polymer composites. Interestingly, a low loss tangent (tanδ~0.075) and greatly enhanced ε′ ~ 156 with low temperature coefficient (Δε' ~ 8.65%) at 150 °C were obtained in Na1/3Ca1/3Bi1/3Cu3Ti4O12/PVDF composites with 50 vol% filler. Theoretical prediction of the effective ε′ of composites was performed to clarify the origins of the improved dielectric properties. Accordingly, the largely enhanced ε′ resulted from the high–permittivity of Na1/3Ca1/3Bi1/3Cu3Ti4O12 particles used and from interfacial polarization in the composites, while the low value of tanδ was due to the initially low tanδ values of filler ceramics particles.

Structural and dielectric analysis of (Bi0.5Na0.5Ti0.94Ce0.06O3) 0.85-(CeO2) 0.15 ceramics

A ceramic composite of Bi0.5Na0.5TiO3 (BNT) and CeO2 (maintaining the Ce: Ti ratio of 20:80) has been synthesized by a standard mixed-oxide reaction method. The Rietveld analysis of X-ray diffraction pattern, backscattering scanning electron micrograph, energy dispersive X-ray spectroscopy, and Fourier transform infrared spectra reveal the formation of the two-phase composite (Bi0.5Na0.5Ti0.94Ce0.06O3) 0.85-(CeO2) 0.15. The estimated optical band gap of the composite is found to be 2.72 eV. In the high-temperature range, the dielectric constant of the composite (4133 at 1 kHz) is significantly higher than that of BNT (1586 at 1 kHz). The static and infinite frequency dielectric constant and the relaxation distribution parameter for both the grain and grain boundary contributions have been determined from the Cole-Cole plot. The contribution of Debye-type relaxation for each of the grain and the grain boundary component and the DC conductivity to the loss tangent have been resolved. The fabricated composite has provided low dielectric loss and enhanced ferroelectric properties.

Low temperature synthesis and dielectric characterisation of La2Mo2O9 ceramic at RF and microwave frequencies

ABSTRACT Using a simple solid-state mixed oxides method, dense La2Mo2O9 ceramics with a relative density higher than 94% were prepared at relatively low sintering temperatures (<960°C) and the crystal structure, dielectric properties were studied in some details. Splitting peaks in XRD profiles evidenced the presence of monoclinic phase. Optimum dielectric properties at microwave frequency were achieved in the best-sintered sample at 920°C, with a moderate relative permittivity of 20.6, a temperature coefficient of the resonance frequency of −38 ppm/°C, but a relatively low quality factor Q×f ∼ 7,160 GHz (f = 9.7 GHz). Complex impedance analysis revealed a thermally activated process derived from the successive short-distance diffusion of oxygen vacancies in the present La2Mo2O9 ceramics, accounting for the low quality factor.

Study of CuO and V2O5 Effect on IR Spectra of Polycrystalline Bismuth Niobate

Bismuth niobate (BiNbO4) ceramics were fabricated by mixed oxide method and sintered by presureless sintering method. BiNbO4 ceramics doped with V2O5 additive in amount 0.125 wt%, 0.250 wt% and 1 wt% of was sintered at T = 910°C whereas BiNbO4 ceramics doped with 2 wt% of CuO additive was sintered at T = 890°C and T = 910°C. It was found that V2O5 additive improved morphology of the ceramic samples. However, the chemical composition of BiNbO4 ceramics in relation to bismuth oxide and niobium oxide manifested a tendency of lack of Bi2O3 component. Absorption bands for the BiNbO4 compound were identified. FTIR band positions associated with NbO6 octahedra suggested that the crystal structure changes after V2O5 incorporation.