Formation Of Single Perovskite Phase Research Articles

Mechanochemical Synthesis of Soft Ferromagnetic Perovskite Lanthanum Strontium Manganite (La0.6Sr0.4MnO3)

Nanocrystalline La0.6Sr0.4MnO3 sample with perovskite structure was successfully prepared by mechanochemical synthesis. Mechanical treatment for 10 h followed by annealing at 1100 °C results in the formation of single perovskite lanthanum strontium manganite (LSMO) phase with rhombohedral crystal structure and symmetry. The heat-treated sample crystallite size, calculated from X-ray diffraction pattern, was about 84 nm. The scanning electron microscope images indicated a high degree of fine structure. The formation of single perovskite phase was confirmed by FTIR measurements. The magnetic measurements showed the soft ferromagnetic behavior of the obtained sample. The saturation magnetization was found to be lower than that expected from theoretical calculation for perfect ferromagnetic ordering and lower than the saturation magnetization published for bulk sample. This was explained in the light of the core/shell model of manganite nanoparticles. The obtained sample was found to have a negative coefficient of magnetoresistance at room temperature of about (−3.5%) with the application of 25 kOe magnetic field.

Processing of Y3+-doped Ba(Ce,Zr)O3 by using the sol–gel method assisted with functionalized activated carbon as a composite anode for proton ceramic fuel cells

A functionalized activated carbon derived from palm oil empty fruit bunches is utilized as a dispersing agent to synthesize BaCe0.54Zr0.36Y0.1O2.95 (BCZY) powder, which is used as a composite anode. The characteristics of pristine and modified powders are presented and compared. The Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) results confirm the elimination of the intermediate compounds in both powders, thereby promoting single perovskite phase formation. The field emission scanning electron microscopy (FESEM) image demonstrates that the modified powder has a smaller particle size and less agglomeration than the pristine powder. The modified powder's performance in the composite anode of the anode-supported single cell shows lower ohmic and polarization resistances than pristine powder. The improved electrochemical performance of nickel oxide mixed with modified powder indicates the importance of tailoring the pristine powder microstructure as a composite anode for proton ceramic fuel cells.

Effect of PMN modification on the structural, microstructural, dielectric and ferroelectric properties of BT ceramics

(1-x)BT-xPMN (x = 0, 0.02, 0.04, 0.06, 0.08 and x = 1) ceramic samples were synthesized by solid state reaction route. XRD study confirmed the formation of single perovskite phase of the BT-PMN system. Increase in density with drastic decrease in average grain size was observed with the increase of PMN content. High value of room temperature dielectric constant (εr) with low value of dielectric loss (tanδ) at room temperature and at 10 kHz frequency was obtained in x = 0.06 ceramic samples, however low temperature coefficient of capacitance (from RT to 100 °C) was obtained in x = 0.08 ceramic samples.

Large dielectric response of 0.6PMN-0.4PZN relaxor ferroelectric ceramic for multilayer capacitors

0.6PMN-0.4PZN solid solution ceramic was synthesized employing two stage columbite route using sintering temperature range 1000–1170 °C for calcination temperature 800 °C and 850 °C, respectively. XRD and SEM characterization revealed single perovskite phase formation in ceramic between 1050 °C to 1100 °C. The highest density upto 94% was achieved for the composition under study. The excellent dielectric properties were obtained at lower sintering temperature 1000–1100 °C. Ceramics sintered between 1000 °C–1100 °C exhibit εmax≈14000 and 24000 at 1 kHz with Tc = 51–48 °C which is near room temperature. A good correlation was obtained between dielectric properties with structure, microstructure and density. The TCC values within the limit of Z5U capacitor specification reflect ceramics of composition 0.6PMN-0.4PZN is a potential candidate for MLC.

Crystallization kinetics and growth mechanism of 0.5 (Ba0.85 Ca0.15) TiO3−0.5 Ba (Zr0.1 Ti0.9) O3 powders prepared via solid-state reaction

ABSTRACTThe crystallization kinetics of 0.5 (Ba0.85 Ca0.15) TiO3−0.5 Ba (Zr0.1 Ti0.9) O3 (BCZT) powders, synthesized using conventional solid-state reaction, was investigated by differential scanning calorimetry (DSC) in both non-isothermal and isothermal conditions. In non-isothermal mode, the samples were heated from room temperature to ∼1200°C at various heating rates (2.5, 5, 10 and 15°C/min). In isothermal mode, the powders were firstly heated to 823,833 and 838°C and maintained at those temperatures until complete crystallization. The X-ray diffraction analysis (XRD) confirmed the formation of single perovskite phase. The kinetic parameters of the crystallization of BCZT powders were determined using model-free methods. The application of Johnson–Mehl–Avrami model yields a growth index of 0.5 and an average value of avrami exponent of 2.5, indicating a growth of BCZT particles by diffusion-controlled mechanism with a constant nucleation rate.

Studies on fast and green biodiesel production from an indigenous nonedible Indian feedstock using single phase strontium titanate catalyst

Strontium titanate was synthesized by polymer precursor method and its catalytic activity as heterogeneous basic catalyst was tested in transesterification reaction for high-quality biodiesel production form Madhuca indica oil. The synthesized strontium titanate was characterized by powder X-ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM) attached with Energy Dispersive X-ray Spectroscopy (EDS), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR). Surface area and basicity were also determined using Brunauer-Emmett-Teller (BET)surface area analyzer and Hammett indicator method. The structural characterizations of catalyst enunciated the single perovskite phase formation of well-assorted strontium titanate nanospheres. The transesterification reaction was optimized using one variable at a time (OVAT) and Response Surface Methodology (RSM) using Box Behnkehn Design (BBD) to comprehend the linear effect and interactive effect of process variables on biodiesel production. The optimized reaction condition through OVAT was obtained as: catalyst dose (1.3 wt%), methanol to oil molar ratio (18:1), reaction temperature (65 °C), reaction time (120 min), and agitation speed (600 rpm) while RSM predicted the highest methyl ester conversion at optimum catalyst dose (1.19 wt%), methanol to oil molar ratio (21.5:1), reaction temperature (71 °C), and reaction time (97.7 min). The confirmatory experiment noticed the highest 98% FAME conversion at following reaction conditions catalyst dose (1.2 wt%), methanol to oil molar ratio (22:1), reaction temperature (65 °C), and reaction time (100 min). Confirmatory experiment showed its close agreement with the predicted values from RSM instead OVAT. According to RSM, catalyst dose, reaction temperature, reaction time, and methanol to oil molar ratio were influencing process parameters for transesterification in descending order of their strength. Furthermore, a pseudo-first-order kinetic model was established with the activation energy (Ea) of 65.95 kJ mol−1. The Environmental Factor (E-factor) and Turn Over Frequency (TOF) were also determined and demonstrated the prepared catalyst as a sustainable and potential heterogeneous base catalyst. The physicochemical properties of produced biodiesel were evaluated to check its compatibility with conventional diesel fuel.

Large dielectric response of 0.6PMN-0.4PZN relaxor ferroelectric ceramic for multilayer capacitors

ABSTRACT0.6PMN-0.4PZN solid solution ceramic was synthesized employing two stage columbite route using sintering temperature range 1000–1170°C for calcination temperature 800°C and 850°C respectively. XRD and SEM characterization revealed single perovskite phase formation in ceramic between 1050°C to 1100°C. The highest density upto 94% was achieved for the composition under study. The excellent dielectric properties were obtained at lower sintering temperature 1000–1100°C. Ceramics sintered between 1000°C-1100°C exhibit ϵmax≈14000 and 24000 at 1 kHz with Tc = 51–48°C which is near room temperature. A good correlation was obtained between dielectric properties with structure, microstructure and density. The TCC values within the limit of Z5U capacitor specification reflect ceramics of composition 0.6PMN-0.4PZN is a potential candidate for MLC.

Piezoelectric and dielectric properties of Pb0.93La0.02Sr0.05(Zr0.52Ti0.48)O3 ceramics doped with Li2CO3 at low sintering temperature

Pb0.93La0.02Sr0.05(Zr0.52Ti0.48)O3 (PLSZT) ceramics were successfully doped with various amounts of Li2CO3. The effect of Li2CO3 as sintering aid on crystallization process of PLSZT ceramic was also determined by thermal analysis (TGA/DTA). As the amount of Li2CO3 increased from 0.1 to 1mol%, the sintering temperature was found to decrease from 1150 to 850°C. Li2CO3 addition improved the densification and increased the average grain size. XRD data revealed the formation of single perovskite phase in all compositions. The effects of Li+ doping on the piezoelectric and dielectric properties of PLSZT ceramics were also investigated in which the piezoelectric and dielectric properties were found to be enhanced with the increase in Li+ content. The best piezoelectric and dielectric properties were obtained for 0.7mol% Li2CO3 with ρ=7.421g/cm3, KP=0.46, d33=259 (pC/N), εr=1270, and tan δ=0.0847.

Synthesis and characterizations of BNT–BT and BNT–BT–KNN ceramics for actuator and energy storage applications

Dielectric and ferroelectric properties of 0.93Bi0.5Na0.5TiO3–0.07BaTiO3 (BNT–BT) and 0.93Bi0.5Na0.5TiO3–0.06BaTiO3–0.01K0.5Na0.5NbO3 (BNT–BT–KNN) ceramics were studied in detail. An XRD analysis confirmed the single perovskite phase formation in both the samples. Room temperature (RT) dielectric constant (εr) ~1020 and 1370, respectively at 1kHz frequency were obtained in the BNT–BT and BNT–BT–KNN ceramics. Temperature dependent dielectric and the polarization vs. electric field (P–E) studies confirmed the coexistence of ferroelectric (FE) and anti-ferroelectric (AFE) phases in the BNT–BT and BNT–BT–KNN ceramics. Substitution of KNN into the BNT–BT system decreased the remnant polarization, coercive field and the maximum strain percentage. The energy storage density values ~0.485J/cm3 and 0.598J/cm3 were obtained in the BNT–BT and BNT–BT–KNN ceramics, respectively. High induced strain% in the BNT–BT ceramics and the high energy storage density in the BNT–BT–KNN ceramics suggested about the usefulness of these systems for the actuator and the energy storage applications, respectively.

Dielectric, ferroelectric and bipolar electric field induced strain properties of MPB composition of NBT-xKNN system

(1-x) (Na0.5Bi0.5TiO3)-xK0.5Na0.5NbO3/NBT-xKNN [x = 0.07, 0.06, 0.05] ferroelectric ceramics were prepared by solid state synthesis route (SSSR). The effects of KNN contents on the microstructure, dielectric, piezoelectric and ferroelectric properties of the NBT-xKNN system were investigated in detail. For single perovskite phase formation, the calcination temperature was optimized at 800 °C for 6 h. From the XRD study, the morphotropic phase boundary (MPB) was confirmed for x = 0.07 composition. For better densification, the sintering temperature was optimized for 1150 °C for 4 h. SEM micrographs illustrate the closely packed and non-uniform distribution of grains. Diffusive type of behaviour was observed in all the ceramics. Polarization (P) vs. electric field (E) study confirmed the ferroelectric nature of the NBT-xKNN ceramics. The bipolar field-induced strain measurement for all the ceramic samples showed butterfly-shaped loops indicating their piezoelectric nature. Among all the different compositions in MPB region, high dielectric constant (er) of ~ 3011, high remnant polarization (P r ) of 17.88μC/cm2 and high strain % of 0.41, were obtained in NBT-xKNN system with x = 0.07 confirming the existence of MPB at this composition.

Dielectric and ferroelectric study of KNN modified NBT ceramics synthesized by microwave processing technique

Morphotropic phase boundary (MPB) composition, 0.93Na0.5Bi0.5TiO3–0.07K0.5Na0.5NbO3/NBT–KNN was synthesized by microwave heating. The optimized calcination conditions for single perovskite phase formation were 800°C for 40min, whereas the sintering was carried out at 1150°C for 20, 30 and 40min. The MPB composition, sintered for 30min, showed better properties: nearly uniform and larger grain size of ∼2.52μm, room temperature (RT) dielectric constant (εr) ∼1180 at 1kHz, a relatively high bulk density (ρ) ∼5.49g/cc, remnant polarization (2Pr) ∼3.3μC/cm2 and coercive field (Ec) ∼5.8kV/cm. Diffuse phase transition was observed for all the ceramics with highest diffusivity factor, γ∼1.65 in MPB composition sintered for 30min.

Dielectric and piezoelectric properties of low temperature synthesized iso-valent modified BT ceramics

Ba(1−x)YxTiO3 (where Y=Ca, Mg and Sr, x=0.02, 0.04, 0.06 and 0.08) ferroelectric ceramic samples were synthesized in single perovskite phase by modified solid state reaction (MSSR) route. For single perovskite phase formation and dense grain morphology, 900°C and 1300°C were optimized as calcination and sintering temperatures. With the increase of substitutions% of Ca in BCT ceramic samples, the position of Tc increases slightly, whereas with the increase of Mg and Sr substitution% in BMT and BST systems, the position of Tc decreased but remains above RT. Decreased processing temperature with low temperature coefficient of capacitance made BCT ceramic samples useful for dielectric applications. Symmetric nature of the S–E loops indicated the increase of piezoelectric nature with the increase of Ca substitution% in BCT system.

Nanostructured MIEC Ba0.5Sr0.5Co0.6Fe0.4O3−δ (BSCF5564) cathode for IT-SOFC by nitric acid aided EDTA–citric acid complexing process (NECC)

Ba0.5Sr0.5Co0.6Fe0.4O3−δ(BSCF5564) was synthesized by nitric acid aided EDTA–citric acid complexing sol-gel method (NECC). Both, the phase formation temperature and time of BSCF5564 synthesized NECC were found to be low i.e. single perovskite phase formation temperature is 200 °C less as compared to the conventional method of synthesis. The orthorhombic perovskite structure has been formed after calcination at 800 °C for 5 h. Scanning electron microscopy reveals the formation of porous material constituting nano-sized and irregularly shaped rod-like structure with particle size approximately ranges from 90 to 160 nm. The total weight loss of the BSCF5564 sample comes out to be 6.6%, indicating that quadrivalence state Co4+ and Fe4+ in the sample have been completely reduced to the trivalent state Co3+ and Fe3+ due to thermal analysis. The value of Ea for BSCF5564 prepared by NECC was 0.2288 eV. The electrical conductivity of BSCF5564 synthesized by NECC is observed to be steady at high temperature (above 700 °C).

Structural and Electrical Properties of Microwave Processed Ag Modified KNN-LS Ceramics

Microwave processing steps of 0.95[(K0.5Na0.5)0.94Ag0.06NbO3]-0.05[LiSbO3]/(KNAN-LS) lead free ferroelectric ceramics were optimized for better densification and electrical properties. Calcination temperature and time for single perovskite phase formation were optimized and found to be 850 °C for 60 min., respectively. Crystal structural study revealed the presence of mixed structure in the microwave processed (MWP) KNAN-LS ceramics. The sintering of the KNAN-LS ceramics was carried out at 1080 °C for 10 min, 20 min and 30 min, respectively, and the sample sintered for 20 min exhibited best properties.

Role of Sintering Temperature on the Phase Stability and Electrical Properties of 0.94(K0.5Na0.5NbO3)–0.06(LiSbO3) Ceramics

Lead-free 0.94(K0.5Na0.5NbO3)–0.06(LiSbO3) (KNN–LS) ceramics were prepared by conventional solid-state reaction route (CSSR). For single perovskite phase formation the calcination was done at 850 °C for 6 h. Whereas for obtaining dense morphology the sintering of KNN–LS ceramics was carried out at 1060, 1080, 1100, and 1120 °C temperatures for 4 h, respectively. The structural study revealed that with the increase in sintering temperature the structure of the ceramic transformed from pure tetragonal to pseudocubic phase. Scanning electron microscopy (SEM) micrographs indicated that the optimum sintering temperature of the ceramic was found to be 1080 °C. The Curie temperature (Tc) of the KNN–LS ceramic was found to decrease at higher sintering temperature. The development of typical hysteresis loop confirmed the ferroelectric and piezoelectric nature of the KNN–LS ceramics sintered at different temperatures. The KNN–LS ceramics sintered at 1080 °C showed better ferroelectric and piezoelectric properties i.e., remnant polarization (Pr)∼17.2 µC/cm2, coercive field (Ec)∼13.5 kV/cm, piezoelectric coefficient (d33)∼161 pC/N, coupling coefficient (kp)∼0.36 and remnant strain ∼0.06% were obtained.

Investigation of dielectric and electrical properties of Mn doped sodium potassium niobate ceramic system using impedance spectroscopy

A single perovskite phase formation of polycrystalline samples of (Na0.52K0.44Li0.04) (Nb0.86-xTa0.1Sb0.04Mnx) (where x = 0.00, 0.01, 0.03, and 0.05) here by denoted as NKNLST and Mn doped NKNLST were prepared by mixed oxide method. The preliminary structural studies were carried out by x-ray diffraction technique showing the formation of single perovskite phase with orthorhombic symmetry for all compositions. Addition of Mn in NKNLST system lowered the sintering temperature by 75 °C. Detail study of impedance parameters shows the non-Debye temperature of relaxation phenomena in the system. This analysis enables us to separate grain and grain boundary contribution of the materials. Above the ferroelectric–paraelectric phase transition temperature, the electrical conduction is governed by the thermal excitation of carriers from oxygen vacancies exhibiting Negative temperature coefficient (NTCR) behaviour.

IMPEDANCE SPECTROSCOPY AND AC CONDUCTIVITY STUDIES OF FERROELECTRIC (K0.5Na0.5)NbO3 CERAMICS

Lead free (K0.5Na0.5)NbO3 (KNN) ceramics were prepared by conventional solid state reaction route. For single perovskite phase formation, calcination temperature was optimized at 850°C for 6 h, whereas for dense morphology the sintering of the ceramic was carried out at 1120°C for 4 h. X-ray diffraction XRD analysis confirmed the formation of single phase with orthorhombic structure at room temperature. Impedance analysis and AC conductivity studies of the KNN sample was carried out in the temperature range of 703–773 K. Impedance study showed the increase in conducting behavior at higher temperature. The temperature dependence of AC conductivity indicated that the conduction process is due to doubly ionized oxygen vacancies in the higher temperature region.

The Structural, Microstructural, Mechanical and Dielectric Properties of the Li0.1Na0.9NbO3 Ceramics

Polycrystalline samples of Li0.1Na0.9NbO3 were obtained by means of a conventional ceramic technology. The analysis of the X-ray diffraction pattern showed the formation of single perovskite phase with an orthorhombic structure at room temperature. The EDS and EPMA measurements revealed that the sample is perfectly sintered, chemically homogeneous and confirmed its high quality. Elastic constants: Youngs's modulus E, shear modulus G and Poisson ratio ν were determined using an ultrasonic method. The dielectric measurements were performed in heating and cooling processes. It was found that a Li-doping influence dielectric properties. The obtained results indicated that Li0.1Na0.9NbO3 is a promising lead-free material for applications.

Dielectric and Ferroelectric Properties of Ag Modified Lead Free 0.94[KNN]–0.06[LS] Ceramics

Lead-free 0.94[(K0.5Na0.5)0.98Ag0.02NbO3]-0.06(LiSbO3) (KNAN-LS) ferroelectric ceramics, (a morphotropic phase boundary (MPB) composition), was synthesized by both conventional mixed-oxide and microwave processing techniques. The KNAN-LS system was calcined at 850° for 6 h for the formation of single perovskite phase where as the conventional and microwave sintering was done at 1080°C for 4 h and 1050°C for 1 h, respectively. SEM characterization of the microwave sintered ceramics revealed dense and homogeneous packing of grains. The microwave sintered KNAN-LS samples showed better dielectric and ferroelectric properties compared to conventional sintering route.

Characterizations of PMNT 68/32 System Synthesized by Microwave Technique

PMNT 68/32 system was synthesized in single perovskite phase by solid state reaction route. Calcination temperature for single perovskite phase formation was optimized at 700°C. Microwave sintering of PMNT 68/32 sample was done at 1050°C. Dense, uniform and homogeneous morphology with average grain size ∼1 μm was obtained in microwave sintered PMNT 68/32 samples. Room temperature (RT) values of dielectric constant (ϵr) and dielectric loss (tanδ) at 10 kHz were found to be ∼1050 and 0.55. Occurrence of polarization versus electric field (P-E) loop confirmed the ferroelectric nature of the microwave sintered PMNT 68/32 system.