The rare-earth-metal-oxide based electronic materials were produced via a conventional mixed-oxide route. Thermal analysis, XRD and SEM were used to follow phase evolution and demonstrate the phase purity. Analytical TEM were used to analyze crystal structural defects and to track the presence of secondary phases, especially at grain boundaries. A crystal structure determination was also performed. Phonon modes were analyzed with FTIR and Raman spectroscopies and correlated with the origin of dielectric permittivity (εr) and radiation losses (tan δ) characteristics. In some compound and mixed compound Raman band mode exist, but this band is absent in simple perovskite indicating that this band is associated with distribution of B-site cations ordering. Some of compound shows long range order in B-site, while it does not present in other material. A photo-acoustic sampling technique in conjunction with the FTIR spectroscopy was employed, allowing the analysis of neat materials with minimal sample preparation. Measurements of the quality factor (Qf), εr and the temperature coefficient of the resonant frequency (τf) characteristics were made at the microwave resonant frequency using a vector or network analyzer.
These perovskite have low tolerance factor because of considerable size misfit of constituting atoms. For determination of atomic size and characterization of constitution atoms, the test of samples and Rietveld refinement using GSAS programs were used to do this examination. These materials have attractive dielectric properties are being evaluated extensively for substrates for multi-chip-module (MCM) devices and microwave telecommunications.
Polycrystalline bulk samples of PrFe1-xMnxO3 (x=0.0, 0.1, 0.3, 0.5) were synthesized by solid state reaction method to understand their structural, optical and dielectric properties
Silicate ceramics are of considerable promise as high frequency dielectrics in emerging millimetre wave applications including high bandwidth wireless communication and sensing. In this review, we show how high quality factors and low, thermally stable permittivities arise in ordered silicate structures. On the basis of a large number of existing studies, the dielectric performance of silicate ceramics is comprehensively summarized and presented, showing how microstructure and SiO4 tetrahedral connectivity affect polarizability and dielectric losses. We critically examine the appropriateness o…
Lead-free Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) ceramics have demonstrated excellent dielectric, ferroelectric and piezoelectric properties in comparison to lead-based materials. The synthesis of pure and crystalline BCZT nanopowders at low temperatures of 25, 80 and 160 C was reported previously by using a sol-gel method followed by a hydrothermal route. In this study, the structural, dielectric and ferroelectric properties of sintered BCZT ceramics at 1250 °C for 10h were investigated. XRD measurements revealed the presence of a single perovskite phase at room temperature with the coexistence of…
We have measured dielectric properties of Ca$_{1+x}$Cu$_{3-x}$Ti$_4$O$_{12}$ ($x$ = 0, 0.1, 0.5, 1, 1.5, 2, 2.9 and 3), and have found that Ca$_2$Cu$_2$Ti$_4$O$_{12}$ (a composite of CaCu$_3$Ti$_4$O$_{12}$ and CaTiO$_3$) exhibits a high dielectric constant of 1800 with a low dissipation factor of 0.02 below 100 kHz from 220 to 300 K. These are comparable to (or even better than) those of the Pb/Ba-based ceramics, which could be attributed to a barrier layer of CaTiO$_3$ on the surface of the CaCu$_3$Ti$_4$O$_{12}$ grains. The composite dielectric ceramics reported here are environmentally beni…
CaCu3Ti4O12 (CCTO) ceramics which has perovskite structure gained considerable attention due to its giant permittivity. But, it has high tan δ (0.1 at 1kHz) at room temperature, which needs to be minimised to the level of practical applications. Hence, TeO2 which is a good glass former has been deliberately added to CCTO nano ceramic (derived from the oxalate precursor route) to explore the possibility of reducing the dielectric loss while maintaining the high permittivity. The structural, morphological and dielectric properties of the pure CCTO and TeO2 added ceramics were studied using X-ray…
CaxCu3Ti4O12 polycrystalline powders with variation in calcium content were prepared via the oxalate precursor route. The structural, morphological and dielectric properties of the ceramics fabricated using these powders were studied using x ray diffraction, Scanning Electron Microscope along with Energy Dispersive X ray Analysis, Transmission Electron Microscopy, Electron Spin Resonance (ESR) spectroscopy and Impedance analyzer. The X ray diffraction patterns obtained for the x = 0.97, 1.0 and 1.1 powdered ceramics could be indexed to a body centered cubic perovskite related structure associa…
This letter reports microwave dielectric measurements performed in the antiferroelectric phase of NaNbO3 ceramics from 100 to 450 K. Remarkable dielectric relaxations were found within the antiferroelectric phase and in the vicinity of ferroelectric-antiferroelectric phase transition. Such dielectric relaxation process was associated with relaxations of polar nanoregions with strong relaxor-like characteristic. In addition, the microwave dielectric measurements also revealed an unexpected and unusual anomaly in the relaxation strength, which was related to a disruption of the antiferroelectric…
In this work, we report the combined effect of donor (Nd) and acceptor (Li) co-doping at the Zn-site of ZnO ceramics on structural, microstructural and dielectric properties. Combining experimental observations with DFT based theoretical study, we have shown that before experimental fabrication DFT based first principles study can be used as a good indication to have prior qualitative assessment of a dielectric medium. For implementing this objective various Li and Nd co-doped ZnO ceramics have been synthesized through the conventional solid-state reaction route. Quantitative XRD analysis reve…
Based upon a widely-accepted internal-barrier-layer-capacitance (IBLC) model, the dielectric loss in the giant-dielectric-constant CaCu$_{3}$Ti$_{4}$O$_{12}$ (CCTO) material is expected to decrease as the conductivity of the CCTO grains/subgrains increases. In this letter, we report that this idea was successfully realized through the La-for-Ca substitution in the CCTO ceramics. The impedance spectroscopy analysis gives the evidence.
AFe$_{1 / 2}$B$_{1 / 2}$O$_{3}$(A- Ba, Sr, Ca; B-Nb, Ta, Sb) ceramics were synthesized and temperature dependencies of the dielectric permittivity were measured at different frequencies. The experimental data obtained show very high values of the dielectric permittivity in a wide temperature interval that is inherent to so-called high-k materials. The analyses of these data establish a Maxwell-Wagner mechanism as a main source for the phenomenon observed.
We investigate the low temperature behaviour of Pb(In$_{1/2}$Nb$_{1/2}$)O$_{3}$-Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$-PbTiO$_{3}$ using dielectric permittivity measurements. We compare single crystal plates measured in the [001] and [111] directions with a polycrystalline ceramic of the same composition. Poled crystals behave very differently to unpoled crystals, whereas the dielectric spectrum of the ceramic changes very little on poling. A large, frequency dependent dielectric relaxation seen in the poled [001] crystal around 100 K is much less prominent in the [111] crystal, and doesn't occur in …
We report observation of magneto-electric and magneto-dielectric couplings in ceramic Co3TeO6. Temperature dependent DC magnetization and dielectric constant measurements together indicate coupling between magnetic order and electronic polarization. Strong anomaly in dielectric constant at ~ 18K in zero magnetic field indicates presence of spontaneous polarization. Observations like weak ferromagnetic order at lower temperature, field and temperature dependences of the ferroelectric transition provide experimental verification of the recent theoretical proposal by P. Toledano et al., Phys. Rev…
The complex dielectric permittivity of a sintered ceramic tablet consisting of 70.5 % $BiFeO_{3}$ and 27.7% $Bi_{2}Fe_{4}O_{9}$ was analyzed as a function of temperature from -120 °C to 230 °C. The results reveal a complicated dielectric response with temperature activated relaxation features. They also reveal a ferroelectric phase transition that decayed with repeated heating cycles of the tablet. The source of the behaviour is assigned to relaxation processes happening along the grain boundaries of differing compositions in the tablet. The origin of the phase transition is traced to locally …
The nature of the cubic-like state in the lead-free piezoelectric ceramics 0.5K0.5Na0.5NbO3-0.5Na0.5Bi0.5TiO3 (KNN-50BNT) has been examined in detail by synchrotron x-ray diffraction (SD), selected area electron diffraction (SAED), neutron diffraction (ND), and temperature dependent dielectric characterization. The SD pattern of KNN-50BNT presents a pure perovskite structure with pseudocubic symmetry. However, superlattice reflections were observed by SAED and completely indexed by tetragonal symmetry with P4bm space group in ND pattern. The relaxor behavior of KNN-50BNT is compared with Pb-ba…
Dielectric response e*(f,T) and polar phonon spectra of coarse grain (grain size ~ 4 mkm) and fine grain (grain size ~ 150 nm) ceramics of PbMg_(1/3)Nb_(2/3)O3-35%PbTiO3 were investigated at temperatures 10 - 900 K. e*(f,T) in coarse-grain ceramics exhibits relaxor behavior at high temperatures and a sharp anomaly at the ferroelectric phase transition. The fine-grain ceramics exhibit mainly relaxor ferroelectric behavior with a smaller dielectric constant. The difference is explained by different relaxational dynamics of polar nanoclusters, which appear to be more stabilized at high temperatur…
A correlation between structure and vibrational properties related to a ferroelectric to paraelectric phase transition in perovskite Pb(1-x)(Na0.5Sm0.5)xTiO3 (PNST - x) polycrystalline powders is discussed. Substitution leads to reduction of tetragonality which is associated with a shift of the phase transition to lower temperatures. The nature of the phase transition gets diffused with increasing substitution.
Ferroelectric ceramics (Ba0.85Ca0.15)(Ti0.9Zr0.1-xSnx)O3 (x=0.00, 0.02, 0.04, 0.06) were prepared by a sol-gel method. Structural investigation revealed the co-existence of tetragonal (P4mm) and orthorhombic (Pmm2) symmetries at room temperature for the undoped ceramic, while only a tetragonal structure (P4mm) was observed for the doped ceramics. Dielectric measurements indicate a dielectric relaxation process at high temperatures which is essentially related to the hopping of oxygen vacancies. Furthermore, a down shifting of the Curie temperature (TC) with increasing Sn4+ doping rate has been…
A method for evaluating the piezoelectric response of unpoled ferroelectric ceramics from elastic and dielectric measurements is proposed and tested on BaTiO$_3$. The method is based on the observation that the softening in a ferroelectric phase with respect to the paraelectric phase is of piezoelectric origin. The angular averages of the piezoelectric softening in unpoled ceramics are calculated for ferroelectric phases of different symmetries. The expression of the orientational average with the piezoelectric and dielectric constants of single crystal tetragonal BaTiO$_3$ from the literature…
Dielectric study over a broadband was carried out from 10 to 70 K on ceramic Gd1-xYxMnO3 (x= 0.2, 0.3, and 0.4). For all the compositions, a prominent sharp peak about ~18K was observed in the temperature dependence of both ε'(T) and ε"(T) at all frequencies, indicating a long-range ferroelectric (FE) transition. Using Cole-Cole fit to the permittivity data, the relaxation time τ and the dielectric strength Δε were estimated. Temperature variation of τ(T) in the Arrhenius representation is found to be nonlinear (non-Debyean relaxation), with increasing barrier-activation energy over successive…
The efficiency of glass ceramic sealants plays a crucial role in high temperature applications performance and durability, such as oxygen separation from air. In order to develop suitable sealants, operating at about 950C, several glass-ceramics with different compositional additives and ratios in BAS system have been prepared and investigated. The effects of additive oxides, CaO, CoO, B2O3, as network modifiers on the thermal and dielectric properties of BAS glass-ceramic for further oxygen transport membrane OTM applications were evaluated and discussed. The addition of additives has evident…
Dielectric permittivity was studied in ceramics of relaxor ferroelectric bismuth-sodium titanate Na$_{0.5}$Bi$_{0.5}$TiO$_{3}$. The measurements were performed on as sintered and heat treated in vacuum samples. The diffuse dielectric anomalies associated with the structural phase transitions were observed in as sintered samples. The intense peak of permittivity ($ \varepsilon_{\text{max}} \sim 10^{4}$) appeared after heat treating in vacuum. The anomaly of $\varepsilon(T)$ was contributed by slow polarization processes ($f<10$ kHz) and was non-stable, vanishing on heating in air up to $\sim 80…
Structure and dielectric characterization were performed on the (1-x)La(Mg1/2Ti1/2)O3 - xLa2/3TiO3 perovskite ceramics with the actual composition 0<=x<=0.52. The sequence of structure transformations was detected as x is increased: P21/n (0<=x<0.3) - Pnma (0.3<=x<0.37) - Imma (0.37<=x<0.4) - I2/a (0.4<=x<=0.49) - R-3c (0.49<x<=0.52). The structure evolution from the tilt configuration a+b-b- to a-a-a- are considered in terms of competing the repulsive energy and the Madelung energy. Relative permittivity of the ceramics was measured as a function of temperature and LT content. Temperature coe…
Dielectric measurements on 0.65[Pb(Ni_1/3Nb_2/3)O_3]-0.35PbTiO_3 ceramic in the temperature range 90K to 470K shows a relaxor ferroelectric transition around 350K with a Vogel-Fulcher freezing temperature of 338K and appearance of a non-ergodic relaxor ferroelectric phase of tetragonal structure at room temperature. This non-ergodic phase reenters into the relaxor state at low temperatures as evidenced by the appearance of a frequency dependent anomaly in the imaginary part of the dielectric constant around 160K, similar to those reported in other relaxor ferroelectric based morphotropic phase…
We report on the experimental investigation of a high-frequency (1MHz - 1.8GHz) dielectric dispersion in unpoled and poled Pb(Zr,Ti)O3 ceramics. Two overlapping loss peaks could be revealed in the dielectric spectrum. The linear dependence between the lower-frequency peak position and average grain size D, which holds for D< 10mkm, indicates that the corresponding polarization mechanism originates from piezoelectric resonances of grains. The intensity of the higher-frequency peak is drastically reduced by poling. It is thus proposed that this loss peak is related to domain-wall contribution to…
The dielectric properties of tantalum doped BaTi0.85Zr0.15O3 were investigated. The conventional solid state reaction method was used to make the ceramic samples. The composition was close to the pinch point of the three structure phase transitions in BaTiO3. Powder X-ray diffraction result indicated that the samples were in very slightly distorted rhombohedral structure at room temperature, and the dielectric measurement showed only cubic-to-rhombohedral phase transition occurred. Instead of a sharp peak characteristic of a ferroelectric (FE) transition, the large dielectric response was simi…
Microstrctural, vibrational, ferroelectric and dielectric properties investigation reveals non-stoichiometric chemical ordered regions (CORs) and relaxor like dielectric characteristics in lead magnesium niobate (PMN) ceramics uniaxially hot pressed (HP) at 800 oC to 1200 oC. Occurance of (1/2 1/2 1/2) superlattice reflections along <111> in <110> zone axis SAED pattern as well as the presence of bright nano-meter regions in corresponding dark-field images in 800 oC hot pressed PMN demonstrates formation of the CORs as soon as perovskite phase is formed during calcination and remains unaffecte…
The dielectric and structural order-disorder properties of as-sintered complex perovskite (x)Pb(In1/2Nb1/2)O3:(1-x)Pb(Mg1/3Nb2/3)O3 ceramics are highly influenced by the quantity of Pb(In1/2Nb1/2)O3 (PIN). High PIN quantity causes the relative permittivity maxima to decrease and the temperature (Tmax) to increase. Also, strong frequency dispersion is dominant in the relative permittivity plotted against the temperature. In the ferroelectric hysteresis loop measurements, the maximum values of electric displacements (Dmax) decrease with increasing PIN. The ceramics in the composition range x = 0…
Electric Charge Transport and Dielectric Properties of the Barium Titanate Ceramics Obtained by Spark-Plasma Sintering with Different Carbon Content
Institute of Physics of the National Academy of Sciences of Ukraine（乌克兰国家科学院物理研究所）；Educational Scientific Institute of High Technologies, Taras Shevchenko National University of Kyiv（基辅塔拉斯舍甫琴科国立大学高等技术教育科学研究所）；Frantsevich Institute for Problems in Materials Science, National Academy of Sciences of Ukraine（乌克兰国家科学院弗兰采维奇材料科学问题研究所）；Department of Chemistry, Stockholm University（斯德哥尔摩大学化学系）；Department of Physical Materials Science and Heat Treatment, National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”（乌克兰国立技术大学“伊戈尔·西科尔斯基基辅理工学院”物理材料科学与热处理系）
Dielectric behavior and conductivity mechanism in lead-free (100-x)(Li0.12Na0.88)NbO3-xBaTiO3 (0 to x to 40) piezoelectric ceramics were investigated using impedance spectroscopy over a wide temperature (-100 oC to500 oC) and frequency range (0.1 Hz to1 MHz). The grain and grain boundary response as well as the relaxation processes at different frequencies and temperatures were also discussed. A low frequency dispersion in dielectric permittivity (LFDD), a typical characteristic of high-temperature behavior was observed both below and above the ferro-paraelectric phase transition temperature, …
Multiferroic composites with the composition (1-x) BaTi0.8Sn0.2O3 - (x) La0.5Ca0.5MnO3 (x =0, 0.3, 0.5, 0.7, 0.9 and 1) were prepared by sol-gel techniques. Rietveld refinements of the composites with 0-3 and 3-0 type connectivities exhibit the formation of pure phases and confirm the fraction of the composite samples. It was found that the composites grain size decreases slightly with increasing the La0.5Ca0.5MnO3 content. Magnetic measurements of the composite ceramics exhibit a gradual increase in saturation and remanent magnetization with increasing La0.5Ca0.5MnO3 content. Dielectric data …
The structure and dielectric properties of 6% $\rm{Sr}^{2+}$-substituted, modified Lead Zirconium Titanate (PZT) piezoelectric ceramic, with composition $[\rm{Pb}_{0.94}\rm{Sr}_{0.06}][(\rm{Mn}_{1/3}\rm{Sb}_{2/3})_{0.05}(\rm{Zr}_{0.54}\rm{Ti}_{0.46})_{0.95}]O_3$ and lead manganese antimonite as an additional dopant, synthesized by ceramic route have been investigated in a frequency range from 50Hz to 1MHz and in a temperature range between room temperature and 633K. The scanning electron micrograph of the sample taken at the room temperature confirms the formation of a fairly homogenous struct…
Multiferroic (Bi1-xLaxFeO3)0.5(PbTiO3)0.5 ceramics was prepared from mechanical synthesized nanopowders. The XRD studies revealed the tetragonal structure and the tetragonality decreased with La content. Dielectric response of the compounds was found to contain three anomalies: 1) relaxor-like behavior due to lattice disorder (below 300 K); 2) dielectric permittivity maxima at~400 K attributed to the presence of oxygen vacancies; 3) grain boundary effect above 475 K. The Curie point at ~500 K was observed for the compound with x=0.5. The composition near the morphotropic boundary: (Bi0.8La0.2F…
Dielectric response as a function of frequency for high-permittivity dielectric and ferroelectric materials is discussed emphasizing the dynamic behaviour in the microwave and infrared range. After introducing the usual modelling of the polar phonon response and anharmonic hopping in locally dynamically disordered solids, including discussion of displacive and order-disorder ferroelectric phase transitions, we summarised the experimental data for selected ferroelectric, incipient ferroelectric and antiferroelectric perovskite ceramics (STO, BTO, BST, PZO), discussing the dielectric grain size …
(1-x)Pb(Fe1/2Nb1/2)O3-PbTiO3(PFN-xPT)Ceramics with x = 0.13 sintered at 1473K show diffuse phase transition and very high dielectric constant at lower frequencies.The high value of dielectric constant at lower frequencies is shown to be due to the barrier layer formation.The resistivity of the PFN-xPT ceramics, obtained by complex impedance analysis, initially decreases with temperature and then shows an upward trend beyond the ferroelectric Curie point reminiscent of BaTiO3 based thermistors with PTCR effect.
We present dielectric measurements of the colossal dielectric constant material CaCu3Ti4O12 extending up to 1.3 GHz also covering so far only rarely investigated single crystalline samples. Special emphasis is put on the second relaxation reported in several works on polycrystals, which we detect also in single crystals. For polycrystalline samples we provide a recipe to achieve values of the dielectric constant as high as in single crystals.
Lead-free Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) ceramic exhibits excellent dielectric, ferroelectric and piezoelectric properties at the Morphotropic Phase Boundary (MPB). Previously, we demonstrated that the use of the anionic surfactant Sodium Dodecyl Sulfate (SDS, NaC12H25SO4) could enhance the dielectric properties of BCZT ceramic using surfactant-assisted solvothermal processing [1]. In the present study, structural, dielectric, ferroelectric properties, as well as electrocaloric effect and energy storage performances of this BCZT ceramic were thoroughly investigated. X-ray diffraction (XRD) …
Dielectric and magnetic properties of Eu0.5Ba0.25Sr0.25TiO3 are investigated between 10 K and 300 K in the frequency range from 10 Hz to 100 THz. A peak in permittivity revealed near 130 K and observed ferroelectric hysteresis loops prove the ferroelectric order below thistemperature. The peak in permittivity is given mainly by softening of the lowest frequency polar phonon (soft mode revealed in THz and IR spectra) that demonstrates displacive character of the phase transition. Room-temperature X-ray diffraction analysis reveals cubic structure, but the IR reflectivity spectra give evidence o…
A-site deficient Ba$_{0.975}$La$_{0.017}$(ZrxTi$_{0.95-x}$)Sn$_{0.05}$O$_3$ (x = 0.05; 0.20) ceramics (BLaZ100xTS) were synthesized using the solid-state reaction. The microstructural study revealed a high density and low porosity in the studied ceramics. Besides, grain size lower than 1.5 micrometer was observed in the studied compounds, which is due to the incorporation of the rare earth element (lanthanum). X-ray diffraction and Raman studies revealed that BLaZ5TS and BLaZ20TS crystallize in a perovskite-type structure with tetragonal and cubic symmetry, respectively. The dielectric study s…
Ferroelectric glass-ceramics are promising composite materials with dual properties, of high dielectric permittivity and high dielectric breakdown strength. In this context, new phosphate glass-ceramics 2BaO-0.5Na2O 2.5[(1-x)Nb2O5 xWO3]-1P2O5 (x=0, 0.1, 0.2, 0.3 and 0.4) designated as B0, B1, B2, B3, B4 respectively, were prepared by the controlled crystallization technology and then crystallized at high temperature of 760 °C for 10 hours. Subsequently, the obtained glass-ceramics were studied by Differential Scanning Calorimetry (DSC), X-ray powder diffraction (XRD), Raman, impedance spectros…
SrNaBi2Nb3O12 powder was prepared via the conventional solid-state reaction method. X-ray structural studies confirmed the phase to be a three-layered member of the Aurivillius family of oxides. SrNaBi2Nb3O12 (SNBN) ceramics exhibited the typical characteristics of relaxor ferroelectrics, associated with broad and dispersive dielectric maxima. The variation of temperature of dielectric maxima (Tm) with frequency obeyed the Vogel-Fulcher relationship. Relaxor behavior was believed to be arising from the cationic disorder at A-site. Pinched ferroelectric hysteresis loops were observed well above…
The dynamic dielectric nonlinearity of barium strontium titanate (Ba1-x,Srx)TiO3 ceramics is investigated in their paraelectric phase. With the goal to contribute to the identification of the mechanisms that govern the dielectric nonlinearity in this family, we analyze the amplitude and the phase angles of the first and the third harmonics of polarization. Our study shows that an interpretation of the field-dependent polarization in paraelectric (Ba1-x,Srx)TiO3 ceramics in terms of the Rayleigh-type dynamics is inadequate for our samples and that their nonlinear response rather resembles that …
Phase, microstructural, dielectric and ferroelectric properties investigation clearly reveal that the charge imbalance created due to alio-valent Gd3+-ion substitution at Pb2+ site in lead magnesium niobate should be compensated by changing B-site cation ratio instead of creating A-site or B-site vacancies. Microstructure analysis along with elemental mapping exhibit segregation of magnesium oxide (MgO) and gadolinium niobate (GdNbO4) phase, which is observed to remain invariant to the charge compensation mechanism. Fitting of frequency dependent temperature of dielectric constant maximum Tm (…
A novel lead-free tungsten bronze type ceramic Sr5BiTi3Nb7O30, was prepared by a conventional solid-state reaction route. The room-temperature crystal structure shows an average structure with centro-symmetric space group P4/mbm identified by synchrotron XRD. Temperature dependence of dielectric permittivity indicates that Sr5BiTi3Nb7O30 is a ferroelectric relaxor with Tm near 260 K. The ceramic displays stronger frequency dispersion and lower phase-transition temperature compared with Sr6Ti2Nb8O30. A macroscopic and phenomenological statistical model was employed to describe the temperature d…
We describe the development of artificial neural networks (ANN) for the prediction of the properties of ceramic materials. The ceramics studied here include polycrystalline, inorganic, non-metallic materials and are investigated on the basis of their dielectric and ionic properties. Dielectric materials are of interest in telecommunication applications where they are used in tuning and filtering equipment. Ionic and mixed conductors are the subjects of a concerted effort in the search for new materials that can be incorporated into efficient, clean electrochemical devices of interest in energy…
Room temperature dielectric and magnetic properties of BiFeO$_3$ samples, co-doped with magnetic Gd and non-magnetic Ti in place of Bi and Fe, respectively, were reported. The nominal compositions of Bi$_{0.9}$Gd$_{0.1}$Fe$_{1-x}$Ti$_x$O$_3$ (x = 0.00-0.25) ceramics were synthesized by conventional solid state reaction technique. X-ray diffraction patterns revealed that the substitution of Fe by Ti induces a phase transition from rhombohedral to orthorhombic at x $>$ 0.20. Morphological studies demonstrated that the average grain size was reduced from $\sim {~}$1.5 $μm$ to $\sim {~}$200 $nm$ w…
We present the technology of obtaining and the electrophysical properties of a multicomponent material 0.61PMN-0.20PT-0.09PS-0.1PFN:Li (PMN-PT-PS-PFN:Li). The addition of PFN into PMN-PT decreases the temperature of final sintering which is very important during technological process (addition of Li decreases electric conductivity of PFN). Addition of PS i.e., PbSnO_3 (which is unstable in ceramic form) permits to shift the temperature of the maximum of dielectric permittivity. One-step method of obtaining ceramic samples from oxides and carbonates has been used. XRD, microstructure, scanning …
(1-x)Li0.12Na0.88NbO3-xBaTiO3 (0 to x to 0.40) ferroelectric ceramics were prepared using conventional ceramics route and their phase transitional behavior is investigated by using dielectric spectroscopy. The temperature-dependent dielectric permittivity epsilon'(T) shows a diffused ferroelectric-paraelectric transition for all compositions. An acceptable and competent characterizing parameter (D) of diffused phase transition (DPT), defined by Uchino et al. [J Am Ceram Soc 2010;93:4011], was measured and validated. Interestingly, a crossover from diffused ferroelectric phase transition (FE-DP…
Lead-free ba0.85ca0.15zr0.1ti0.9o3 (bczt) ceramic powders were synthesized using the sol-gel method. to achieve high-energy storage and large electrocaloric effect in bulk ceramics the ceramics thickness was reduced. dielectric, ferroelectric, energy storage, and electrocaloric properties were investigated for bczt ceramic with 400 μm. here, pure crystalline structure and homogenous microstructure were identified by xrd analysis and sem measurements, respectively. the dielectric measurements revealed a maximum dielectric constant associated with ferroelectric-paraelectric phase transition. the…
Temperature-dependent dielectric permittivity of lead-free (LixNa1-x)NbO3 for nominal x = 0.04-0.20, prepared by solid state reaction followed by sintering, was studied to resolve often debated issue pertaining to exactness of morphotropic phase boundary (MPB) location along with structural aspects and phase stability in the system near MPB. Interestingly, a diffuse phase transition has been observed in the dielectric permittivity peak arising from the disorder induced in A-site and structural frustration in the perovskite cell due to Li substitution. A partial phase diagram has been proposed …
Bi1-xLaxFe1-xMnxO3 (x = 0.000 - 0.300) ceramics prepared by the tartaric acid modified sol-gel technique have been studied to analyze the effect of composition driven structural transition on the magnetic properties of bismuth ferrite (BiFeO3). It was found that the co-substitution of La & Mn at Bi & Fe sites leads to suppression of impurity phases (Bi2Fe4O9 and Bi25FeO40) which generally appear in BiFeO3. The quantitative crystallographic phase analysis has been carried out by double phase Rietveld analysis of all the XRD patterns which indicates the existence of compositional driven crystal …
The Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramics were successfully prepared by sol-gel process, and sintered at 1420 degree. The effect of sintering times (2, 4 and 6 h) on structural, microstructural, electric properties, energy storage, and electrocaloric effect was systematically examined. X-ray diffraction (XRD) results show that all the samples crystallize in the pure perovskite structure. The morphotropic phase transition from the tetragonal to the orthorhombic phase (T-O) was identified and confirmed by Rietveld refinement. The BCZT ceramic sintered at 1420 degree for 4h possesses a good re…
Dielectric nonlinear response of (PbMg$_{1/3}$Nb$_{2/3}$O$_3$)$_{0.9}$(PbTiO$_3$)$_{0.1}$ (0.9PMN-0.1PT) relaxor ceramics was investigated under different ac drive voltages. It was observed that: (i) the dielectric permittivity is independent on ac field amplitude at high temperatures; (ii) with increasing ac drive, the permittivity maximum increases, and the temperature of the maximum shifts to lower temperature; (iii) the nonlinear effect is weakened when the measurement frequency increases. The influences of increasing ac drive were found to be similar to that of decreasing frequency. It is…
Structural properties, impedance, dielectric and electric modulus spectra have been used to investigate the sintering temperature (Ts) effect on the single phase cubic spinel Ni0.6Zn0.4Fe2O4 (NZFO) ceramics synthesized by standard ceramic technique. Enhancement of dielectric constants is observed with increasing Ts. The collective contribution of n-type and p-type carriers yields a clear peak in notable unusual dielectric behavior is successfully explained by the Rezlescu model. The non-Debye type long range dielectric relaxation phenomena is explained by electric modulus formalism. Fast respo…
Dielectric materials, with high tunability at microwave frequencies, are key components in the design of microwave communication systems. Dense Ba0.6Sr0.4TiO3 (BST) ceramics, with different grain sizes, were prepared in order to optimise the dielectric tunability via polar nano cluster effects. Dielectric permittivity and loss measurements were carried at both high and low frequencies and were supported by results from X-ray powder diffraction, scanning and transmission electron microscopies, Raman spectroscopy and piezoresponse force microscopy. The concentration of polar nano clusters, whose…
