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Mineral materials, such as corundum, quartz and periclase are very often used in technological processes. Due to its characteristics, and chemical reaction in solid state, these minerals form very interesting and useful material, cordierite. The mineral ratio in this compound (MgO : Al2O3 : SiO2) is 2:2:5. They form cordierite, electronic ceramic, which can be sintered in a narrow temperature range, at about 1375 °C. Composition of this electronic ceramics material is is 2MgO-2Al2O3-5SiO2 (MAS) and in this research 20% mass Bi2O3 was added in the aim of decrease the sintering temperature. The effects of sintering, the composition and morphology were followed by x-ray diffraction, scanning electron microscopy and EDS analysis, as a function of sintering temperature. MAS ceramics were sintered at 1000ºC, 1100ºC and 1200ºC.

My comments concern the significant error in the crystallographic part of the commented papers. It was discovered that the studied nanocrystals are of sillenite type and the correct formula should be Bi 25 FeO 39 :Co,Ti and Bi 25 FeO 39 :Ni,Ti instead of BiFeO 3. Moreover, the type of unit cell is not correct. Due to the doping the new type of unit cell, previously unknown, was proposed for such crystals. It was found that the studied sample contains two slightly different phases of the sillenite type. The actual chemical composition of the studied crystals is not known. [ABSTRACT FROM AUTHOR]

My comments concern the significant errors in the crystallographic part of the commented paper. [ABSTRACT FROM AUTHOR]

The structural properties of selected (Ba1−xSrx)PbO3 ceramics were examined at 14–1148 K using X-ray powder diffraction (XRD). These materials are attractive due to their variety of applications, such as, for example, high-temperature thermoelectric energy conversion. Attention was paid to this paper as a continuation of the previous examinations of higher Sr2+ concentrations. The type of perovskite distortion and temperatures of the structural phase transitions (SPTs) were determined from the splitting of certain pseudocubic lines. At this point, for example (Ba0.3Sr0.7)PbO3 showed three temperature-induced SPTs. When the amount of Sr increased in the samples, no phase transition was observed, which is contrary to the data previously demonstrated in the literature. The quality of the ceramics was examined by scanning electron microscopy-energy dispersion X-ray spectroscopy (SEM-EDS), demonstrating their homogeneity and uniform elements dispersion. As a result of profound crystal investigations, confirmed by thermogravimetric analysis and quadrupole mass spectroscopy (TGA-QMS), a phase diagram was prepared for the (Ba1−xSrx)PbO3 system based on our former and recent study. Also, the investigation of a new application for the (Ba1−xSrx)PbO3 family is presented in this paper for the first time. The TGA analysis was conducted on Illinois#6 hard coal to evaluate the capability of perovskites to be used in the chemical looping combustion (CLC) process in a range of temperatures 1073–1173 K. Due to its thermal stability and reactivity, Ba0.9Sr0.1PbO3 is the material with the greatest potential to be applied as an oxygen carrier. The combination of strontium and barium offers encouraging results compared to the pure barium and strontium lead oxide perovskites. [ABSTRACT FROM AUTHOR]

In this paper, the crystallization behavior of 50ZnO:47B2O3:3Nb2O3:0.5Eu2O3 (G-0 h) glass has been investigated in detail by DSC, XRD and TEM analysis. The luminescent properties of the resulting glass-ceramics were also investigated. By XRD and TEM analysis, crystallization of several crystalline phases has been proved (α-Zn3B2O6, β-Zn3B2O6 and ZnNb2O6). By calculating crystal parameters, it was found that europium ions are successfully incorporated in the β-Zn3B2O6. Photo-luminescent spectra showed increased emission in the resulting glass-ceramic samples compared to the parent glass sample due to higher asymmetry of Eu3+ ions in the obtained crystalline phases. It was established that the optimum emission intensity is registered for glass-ceramic samples obtained after 25 h heat treatment of the parent glass. [ABSTRACT FROM AUTHOR]

Copyright of Dyna is the property of Universidad Nacional de Colombia, Medellin, Facultad de Minas and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The paper aims to conduct a novel investigation of some ceramic samples that were taken from Hunedoara's Corvins' Castle (Romania). Some nuclear analytical techniques, such as WDXRF, XRD, neutron diffraction, and neutron tomography, will be used in the investigations. These techniques will be correlated with data from FTIR and Raman spectra. There were experimental data on the mineral and chemical composition that were gathered from the object's surface. Neutron tomography was used to examine the spatial distribution of the phases, while X-ray and neutron diffraction aid in determining the phase composition of the samples under study. The composition of the ceramic samples was identified by the results as follows: quartz, hematite, feldspar, and calcite. Zirconia and titanium dioxide were found in the green pigments. The application of non-destructive techniques that have a high penetration rate into bulk objects seems appropriate in this instance. [ABSTRACT FROM AUTHOR]

In this work we successfully synthesize CsPb(Br x I 1-x) 3 perovskite nanocrystals with different Br/I ratio in a borogermanate glass matrix. The XRD studies show cubic perovskite phase peaks shift as the Br/I ratio changes. The formed nanocrystals have mean size of about 17 nm based on the calculations from the absorption spectra. The smooth change of the Br/I ratio in perovskite nanocrystals allow to obtain luminescence in the range 500–750 nm with quantum yield up to 35 %. The luminescence quantum yield and lifetime of the mixed-halide nanocrystals steadily increase with iodine concentration. Practical application of perovskite glass-ceramics as a radiation converter is shown in the paper. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper aims at exploring the possibility of using a great percentage of recycled materials into vitreous china (VC), thus, contributing to urban waste decrease while lowering the industry's buying costs, previously optimized, for the sanitaryware production. The recycled blend was introduced in the ceramic slip, Sanitser VC, and used in three sanitaryware production plants. This slip let to improve the environmental performances of the overall ceramic production through energy-saving and a decrease in greenhouse gas emissions. In fact, the firing temperature is 80-100 °C lower than traditional production. Therefore, the objective of this paper was to evaluate the firing behavior, technological properties, and microstructure of a typical industrial vitreous china body in comparison with Sanitser VC. The analytical results confirmed the force of this idea and highlighted the advantages of the choice made. [ABSTRACT FROM AUTHOR]

This paper investigates the processes of phase formation of solid solutions of (1 − x)BaTi0.85Zr0.15O3 − xAgNbO3 where x = 0, 0.03, 0.06, 0.09. The optimal temperatures of synthesis and sintering are determined. From the results of X-ray diffraction analysis, it follows that all solid solutions have a perovskite-type structure. Analysis of the microstructure showed that the average grain size decreases at concentrations x = 0.03 and 0.06. Correlations between the cationic composition and dielectric characteristics of the studied solid solutions have been established. The values of the total stored energy and efficiency are determined. The maximum stored energy was found for a solid solution with x = 0.03 and amounted to 0.074 J∙cm−3 with an efficiency of 76.5%. [ABSTRACT FROM AUTHOR]

In this paper was synthesized a bioceramic material based on calcium and phosphorus. Also, the effect of synthesis parameters on the structure and properties of the obtained powders has been studied. In this sense, the stirring speed and the aging time of the precipitates, in the case of some hydroxyapatite powders, are studied. The results show products with the desired characteristics, in terms of structure and composition of analyzed powders. [ABSTRACT FROM AUTHOR]

In this paper, Pb1-xFex(Zr0.52Ti0.48)O3 (PFZT) nano-size powders, in which x changed from 0.00 up to 0.20, were synthesized, using the sol-gel method. The PFZT samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and impedance spectroscopy. According to the experimental results, a combination of rhombohedral and tetragonal symmetries was seen in all the samples. The SEM investigation indicated that the grains were homogeneous with regular morphology, and the average grain size changed with Fe concentration. The dielectric characterizations showed that the dielectric permittivity increases with increasing temperature, and the Fe amount shifts down the temperature of transition. Moreover, a dielectric resonance phenomenon is observed for all the PFZT ceramics. [ABSTRACT FROM AUTHOR]

This paper deals with the synthesis of a series of zirconoaluminosiloxane (ZAS) as monophasic liquid precursors in toluene for zirconia/mullite ceramics. Precursors are synthesized by the zirconium modification of aluminosiloxane. The effect of zirconium incorporation in the aluminosilicate network is studied by FTIR, NMR, and TG/DTA analysis. 29Si and 27Al clearly indicates that zirconium is chemically bonded to the aluminosilicate network and the network connectivity increases with increase in zirconium content. 27Al NMR also reveals the progressive distortion of octahedral symmetry of AlO 6 due to zirconium incorporation, validating the insertion of Zr through Al–O–Zr bonds where Al is four coordinated. These observations attest the monophasic nature and the chemical homogeneity of the synthesized precursors, which is the main factor contributing to the low temperature crystallization of ceramic phases. Ceramic conversion studies of the precursors confirmed the formation of crystalline zirconia/mullite ceramic phases at a low temperature of 900 °C. The XRD and microstructure analysis by SEM/EDX indicated that the mullite crystallization can be controlled by zirconia incorporation. This effect is discussed in terms of the occupancy of zirconia either as intra-granular or inter-granular particles. The zirconia concentration for maximum crystallization of mullite is optimized. [Display omitted] [ABSTRACT FROM AUTHOR]

The paper studies the effect of Li2SiO3/Li4SiO4 phase formation in lithium-containing ceramics on the strength and thermophysical characteristics of lithium-containing ceramics, which have great prospects for use as blanket materials for tritium propagation. During the phase composition analysis of the studied ceramics using the X-ray diffraction method, it was found that an increase in the lithium component during synthesis leads to the formation of an additional orthorhombic Li2SiO3 phase, and the main phase in ceramics is the monoclinic Li4SiO4 phase. An analysis of the morphological features of the synthesized ceramics showed that an increase in the Li2SiO3 impurity phase leads to ceramic densification and the formation of impurity grains near grain boundaries and joints. During determination of the strength characteristics of the studied ceramics, a positive effect of an increase in the Li2SiO3 impurity phase and dimensional factors on the strengthening and increase in the resistance to external influences during compression of ceramics was established. During tests for resistance to long-term thermal heating, it was found that for two-phase ceramics, the decrease in strength and thermophysical characteristics after 500 h of annealing was less than 5%, which indicates a high resistance and stability of these ceramics in comparison with single-phase orthosilicate ceramics. [ABSTRACT FROM AUTHOR]

In our present paper, the morphological, structural and electrical properties of chromium-doped BaTiO 3 ceramics were investigated. BaTi 0.5 (Cr 0.33 Mo 0.17)O 3 was prepared by the sol-gel technique. Tetragonal phase with P4mm space group was observed by X-ray diffraction analysis. An excellent agreement between the calculated and the observed model was verified by Rietveld refinement. A polycrystalline compound with a particle size of 1.96 μm was identified using scanning electron microscopy. The electrical conductivity graph is divided into two regions in the frequency interval 102–106 Hz over the temperature range 480–640 K. The Ac conductivity spectrum follows the Jonscher's law. The conductivity mechanism in the studied temperature range can be explained by the Non-overlapping Small Polaron Tunnel (NSPT) model. The imaginary parts of impedance show that the maximum value of Z″ decrease with temperature rise, reflecting the progressive loss of insulating properties. In addition, the peaks of Z″ shifted to higher frequencies, indicating relaxation behaviour. Furthermore, the real part of Z″ decreased with temperature and frequency increase, indicating Negative Temperature Coefficient Resistance (NTCR) behaviour. The complex impedance plot showed large semicircular arcs corresponding to the merging of two semicircles due to grain and grain boundary contribution. Examination of the impedance and modulus normalization curves revealed a shift in both peaks, indicating the existence of a short moving carrier. The exponent "n" increased with temperature increase, which proves the existence of the Non-overlapping Small Polaron Tunnel (NSPT) model in the studied temperature range. [ABSTRACT FROM AUTHOR]

This paper reports the effect of lanthanum addition on the structural and electrical properties of (Pb 1-x La x)(Zr 0.65 Ti 0.35)O 3 (PLZT x/65/35, x = 8%,10%,12%,15%) ceramics near the morphotropic phase boundary. Studies were conducted on the PLZT x/65/35 ceramics synthesized via a combinatorial approach of high-energy ball milling (mechanical activation method) followed by Cold Isostatic Pressing (CIP). Due to the application of CIP, PLZT ceramics exhibited improved density and a closely packed microstructure. The SEM analysis showed that PLZT x/65/35 ceramics exhibited an increase in grain size with higher concentrations of La3+ ions. Room temperature X-ray diffraction results revealed the formation of perovskite PLZT phase. The investigation on temperature-dependent dielectric, ferroelectric properties of PLZT x/65/35 ceramics provided experimental confirmation of structures cited in XRD analysis. Among all the compositions, PLZT 8/65/35 samples showed a well saturated, uniform P–E hysteresis loop with a high remanent polarization (P r). Poled PLZT 8/65/35 samples displayed electric field induced large strains with limited hysteresis. Piezoelectric charge coefficients (d 33), electromechanical coupling factors (k p , k 33 , k 31) were determined for poled PLZT x/65/35 ceramics and it was found that PLZT 8/65/35 ceramics reveal properties superior to other compositions. Furthermore, the unipolar strain, P r , d 33 , k p , k 33 , k 31 values of PLZT 8/65/35 composition exceeded the previously reported ones for the same composition prepared via sol-gel synthesis technique. [ABSTRACT FROM AUTHOR]

It is thought that the sintering of high‐entropy (HE) ceramics is generally more difficult when compared to that of the corresponding single‐component ceramics. In this paper, we report a novel approach to densify the HE carbide ceramics at relatively low temperatures with a small amount of silicon. Reactive spark plasma sintering (SPS) was used to densify the ceramics using powders of HE carbide and silicon as starting materials. Dense ceramics can be obtained at 1600 ‐1700°C. X‐ray diffraction analysis reveals that only non‐stoichiometric HE carbide phase with carbon vacancy and SiC phase exist in the obtained ceramics. The in‐situ formed SiC phase inherits the morphology of the starting silicon powder owing to the slower diffusion of silicon atoms compared to that of the carbon atoms in HE carbide phase. The mechanical properties of the prepared ceramics were preliminarily studied. [ABSTRACT FROM AUTHOR]

Cr 3 AlB 4 is one of the attractive compounds for high-temperature constrictive ceramics due to its combination of properties typical for ceramics or metals. In this study, the formation mechanism of Cr 3 AlB 4 , presented in the literature, was confirmed by means of the following analyses: XRD, DSC and SEM. According to them the synthesis of Cr 3 AlB 4 occurs is multi-step process with CrB 2 being formed first, followed by Cr 3 B 4 , which is intercalated by aluminium to form Cr 3 AlB 4. Furthermore, most scientific papers do not consider the possibility of synthesising MAB phase from the powders containing amorphous phase. In presented work, possibility of synthesis of Cr 3 AlB 4 from the powders containing the amorphous phase and influence of this kind of raw powders on synthesis process is shown. [ABSTRACT FROM AUTHOR]

In this paper, (1- x)CaBi 2 Nb 2 O 9 - x Na 0.5 Bi 2.5 Nb 2 O 9 [(1- x)CBN- x NBN; x = 0, 0.1, 0.3, 0.5 and 0.7] ceramics were prepared by the traditional solid-state method. The structure and properties of CBN and NBN are very close to each other, and XRD shows that Na/Bi ions have entered the lattice of CBN. By adjusting the content of NBN in (1- x)CBN- x NBN ceramics, the crystal structure of the ceramics undergoes a pseudo-tetragonal distortion that can significantly improve thermal stability. Analysis of the data of XRD refinement confirms there is pseudo-tetragonal phase at x = 0.1 to 0.5. Moreover, the remnant polarization P r is obviously improved due to the reduction of grain size and pseudo-tetragonal distortion. Although the Curie temperature of the CBN-NBN piezoelectric ceramics decreases, the tan δ at high temperatures is significantly reduced and the DC resistivity is increased. The 0.5CBN-0.5NBN ceramic shows excellent comprehensive properties: d 33 of 13.8 pC/N, T c of 873 °C, tan δ of 2.1% at 500 °C, and P r of 8.92 μC/cm2, especially the d 33 maintains 94.9% of the initial d 33 after depolarization at 850 °C, which has competitiveness in the high-temperature piezoelectric materials. [ABSTRACT FROM AUTHOR]

In this paper, Ba(Mg1/3Nb2/3)O3 (BMN) ceramics with x (x = 0–9) wt% BaWO4 were synthesized using the conventional solid-state sintering technique. Effects of BaWO4 addition on the microstructure and microwave dielectric properties of BMN ceramics were evaluated. X-ray diffraction (XRD) analysis showed that there were three phases: main crystalline phase Ba(Mg1/3Nb2/3)O3 and secondary phases BaWO4 and Ba5Nb4O15. Meanwhile, the (100) super-lattice reflection peaks shifted to a higher 2θ angle with increasing BaWO4 content. SEM photographs suggested that BaWO4 working as a sintering additive promoted the densification and grain growth. The dielectric properties were examined by Vector network analyzer. The dielectric constant (εr) was largely determined by the relative density and phase composition. Meanwhile, the addition of BaWO4 had a positive effect on the Q × f value, for example the specimen with x = 5 possessed the highest Q × f value of 111,300 GHz. Optimum microwave dielectric properties (εr = 31.7, Q × f = 111,300 GHz (f = 8 GHz) and τf = 0.16 ppm/°C) were obtained for the specimen with x = 5 sintered at 1350 °C for 6 h. [ABSTRACT FROM AUTHOR]

Copyright of Documenta Praehistorica is the property of Documenta Praehistorica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper is focusing basically on the ceramic technology, of which several methods for the synthesis of MgAl2O4 have been investigated. The synthesis conditions regarding the powders cleanliness, microstructure, and sintering parameters of MgAl2O4 were studied. MgAl2O4 powder was synthesized via conventional solid‐state route using different milling process: vertical attrition milling, WAB as a high‐energy horizontal attrition milling, and Pulverisette as a planetary ball miller, and via solution combustion route using Urea, Glycine, and a mixture of Urea/Glycine. Urea and Glycine was used as fuel. The white powders were obtained for all solid‐state routes and for Urea‐combustion technique. The black and gray powders were obtained in the case of combustion technique, respectively, using a fuel of Glycine and Glycine/Urea mixture. The obtained powders and pellets were characterized by XRD, SEM, and Dilatometry. The results show that, among all the solid‐state route processes, wet attrition milling gives the better and clean spinel phase. The WAB milling and Pulverisette miller introduce a contamination by some yttria‐stabilized zirconia balls in the corresponding powder. Furthermore, the flash combustion technique permit to have nanoparticles with a dense spinel phase of MgAl2O4 and with lower sintering temperature in less time and with no calcination step. This study compare the synthesize of MgAl 2 O 4 as electroceramic materials by different methods, in particular solution combustion routes and conventional solid state. The synthesis conditions regarding the powders cleanliness, microstructure, and sintering parameters of MgAl 2 O 4 were studied [ABSTRACT FROM AUTHOR]

In this paper, the (1−x)BaTiO3-xBi(Zn1/2Zr1/2)O3 (x = 0.04-0.20) solid solutions were prepared using conventional solid-state reaction method. The X-ray diffraction results showed that all samples were crystalized as the perovskite structure, and there was no secondary phase in whole compositional range. For x = 0.04, the ceramics were in tetragonal phase, and transformed to a pesudocubic phase for x ≥ 0.08 at ambient temperature. Temperature-dependent dielectric measurements indicated a crossover from ferroelectric behavior to relaxor-like characteristics. As the BZZ content increased, the polarization-electric field (P-E) hysteresis loops became slimmer, and the discharge energy density increased firstly, but dropped. For x = 0.12, the maximum discharge energy density was 0.758 J/cm3 at 100 kV/cm, and the corresponding energy efficiency was 98%, indicating that (1−x)BaTiO3-xBi(Zn1/2Zr1/2)O3 ceramics were promising candidates for energy storage applications. [ABSTRACT FROM AUTHOR]

CoCuCrO (0 ≤ x ≤ 1) ceramic samples have been characterized by room-temperature X-ray diffraction and relative dielectric permittivity ɛ( T) and loss tangent tanδ( T) measurements (at frequencies from 0.1 to 200 kHz) in the range 100-350 K. The samples were shown to consist of spinel solid solutions with a cubic (0 < x < 0.53) or tetragonal (0.53 < x < 1) structure. Increasing the Cu content of the samples increases their tanδ and electrical conductivity and produces anomalies in the temperature dependences ɛ( T) and tanδ( T) due to dielectric relaxation processes. CoCuCrO:0.01FeO samples were characterized by Mössbauer spectroscopy in the range 77-290 K and shown to be in a magnetically ordered state at 77 K. [ABSTRACT FROM AUTHOR]

In this paper, the Li3(Mg1−xNix)2NbO6 (0.02 ≦ x ≦ 0.08) ceramics are prepared by a solid state reaction method. The effects of Ni2+ substitution on the microwave dielectric properties, microstructure and sintering properties are investigated systematically. The XRD patterns reveal that all the samples could form solid solution with a single Li3Mg2NbO6 phase in the sintering process. The variation in Q × f values is similar to that in bulk density, and tremendous improvement of Q × f values could be attributed to bigger grains and high densification. Since the more polarizable Mg2+ ion is replaced by the less polarizable Ni2+ ion, the permittivities decrease almost linearly with increasing Ni2+ content. Otherwise, with the x value increase from 0.02 to 0.08, the τf values could be effectively adjusted to near zero, but the decreasing porosity-corrected permittivities would damage the stability of crystal structure, which make the τf values shift toward the negative direction. In general, the Li3(Mg0.96Ni0.04)2NbO6 ceramics sintered at 1175 °C for 6 h exhibit superior microwave dielectric properties of εr ~ 15.22, Q × f ~ 126,784 GHz, τf ~ − 2.63 ppm/°C, which demonstrate that the ceramics could be selected as a promising low loss and temperature stable material for future application. [ABSTRACT FROM AUTHOR]

Clay minerals have a great influence on the resulting properties of ceramic bodies. Fly ash as a waste material from burning black coal in power plants is a potentially valuable source of oxides (Al2O3, SiO2 or Fe2O3) for this production. Considering the process of ceramic firing, it is important to understand the thermal behavior of individual ingredients. The thermal behavior of natural smectite minerals (montmorillonite, beidellite, hectorite and nontronite) and their mixtures with added fly ash at different ratios (10%, 30% and 50%) was investigated. The phase analysis was obtained using X-ray diffraction and FT-IR spectroscopy. Under heating to 1200 °C, the structural changes of smectites were divided into four steps including dehydration, dehydroxylation, decomposition and crystallization of new phases. The addition of fly ash caused a shift in the reaction temperatures for all the mentioned phases. These changes were most noticeable for mixtures with hectorite; on the contrary, they were least noticeable for beidellite mixtures. Total mixture mass loss continually decreased with increasing fly ash amount. The obtained experimental thermal data can be applicable not only in the production of ceramic bodies or energy waste processing but also in construction and ensuring the safety of municipal waste landfills. [ABSTRACT FROM AUTHOR]

A glass with the nominal composition of 28Y48Si24Al83O17N (in equal percentage) was chosen as parent glass in this paper to prepare YAlO-based glass-ceramics. Differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to assess the crystallization process of the parent glass. YAG as the only crystalline phase appears in all glass-ceramics produced under 1250°C. A small amount of O'-Sialon secondary phase starts to precipitate from parent glass samples as heat treatment temperature increases to 1250°C. Grain size of the dendrite crystal which corresponds to YAG phase increases and the dendrite branches get thickened as heat treatment temperature increases. Moreover, grain size of YAG phase resulting from two-stage heat treatment is much smaller than that of YAG phase obtained by one-stage heat treatment. The results are relevant to developing improved crystallization treatments for glasses with potential for crystallization to YAG-based glass-ceramics and for heat treatments of YAG/ β-SiAlON materials. [ABSTRACT FROM AUTHOR]

This paper investigates the thermal transformation of powders of volcanic tuffs that are used as building stones and aims at thermally transforming them into ceramics. The following positive indications concerning this thermal transformation were found: (1) the structural evolution which brings products similar to traditional ceramics, (2) the good ability to give rise to dense and compact final products, and (3) the good mechanical properties and the lovely appearance of the final products. Nevertheless, the high values of linear shrinkages recorded in this work seem to strongly hinder the thermal transformation of this powder-like waste into ceramics. However, mixing this by-product with other powder-like waste exhibiting higher-dimensional stability, such as those deriving from sawing of granites, appears proper. [ABSTRACT FROM AUTHOR]

Due to the dominance of non-densifying sintering mechanisms (surface diffusion and evaporation condensation) pure tin oxide ceramics exhibit unusual sintering behavior that allows sintering without shrinkage, i.e. without changes in porosity. It is therefore ideally suited for fundamental studies. In this paper we study the crystallite size and its changes as a function of temperature and dwell time via X-ray diffraction (XRD) line broadening. It is shown that, although the contribution of microstrain broadening is negligibly small, the difference between the different evaluation methods (Scherrer equation, Williamson-Hall plots, Halder-Wagner plot) is quite large. Nevertheless similar qualitative conclusions can be drawn irrespective of the specific evaluation method used (although Halder-Wagner analysis is most reasonable). Significant crystallite growth can be expected for pure tin oxide ceramics from nanosized powders only at temperatures above 1000 °C. Prolonging the dwell times beyond 3 h does not affect the crystallite size to any significant degree. [ABSTRACT FROM AUTHOR]

In this paper, the optical absorption and radioluminescence ( RL) of polycrystalline ceramic and powder Ca WO4 are studied. The samples were synthesized via a solid-state method. Differential thermal analysis and thermogravimetric ( DTA/ TG) measurements indicate a minimum temperature of 700°C for calcination of precursors. The crystalline phase of the samples of calcium tungstate was investigated by X-ray diffraction ( XRD). The RL of the crystal powder and ceramics are in agreement with that present in the literature for bulk single crystals, presenting a single emission band centered at 420 nm when irradiated with β-rays. UV-vis absorption spectroscopy shows that the maximum absorption band of the Ca WO4 sample is at around 400 nm, indicating the presence of mixed valence states of W5+ and W6+, associated with a possible breaking of structural symmetry caused by WO4 tetrahedral distortion. [ABSTRACT FROM AUTHOR]

The oppida from Alarcos and El Cerro de las Cabezas (Ciudad Real, Spain) were two of the most important Iberian sites in the Proto-history (8th-3th centuries BC.) from the Northern Oretania. Archaeological studies have been published since the 80s; however this paper is the first that provides archaeometric results from the chemical and mineralogical analysis of 107 ceramic fragments of Iberian common pottery. They have been analysed through X-ray diffraction (XRD) and X-ray fluorescence (XRF). From the chemical results, a statistical study has been carried out, which has allowed to create the reference groups (RG) and to determine the economic relationships between the two sites studied and their influence areas. At a technological level, the results from the mineralogical analysis have allowed to estimate the firing temperature (EFT) and to classify the ceramic fragments into 3 fabrics with their respective temperature ranges. [ABSTRACT FROM AUTHOR]

The present paper is centred around the investigation of the structural, electrical, and magnetic properties displayed by the novel perovskite polycrystalline La 0.7 Pb 0.3 Mn 1−y V y O 3 (y = 0 – 0.1) prepared via the conventional solid-state technique. The structural properties of the samples were assessed through the utilisation of X-ray diffraction (XRD) analysis. Subsequently, the obtained diffraction data underwent refinement employing Rietveld refinement techniques in order to determine the structural parameters of the samples a , b , c , V and Mn–O bond length and angle. The study of X-ray diffraction (XRD) peaks reveals that all the samples exhibited crystallization in a single phase, devoid of any impurities. All of the samples exist in rhombohedral orientation with a space group of R-3c. The tolerance factor of the samples was calculated in order to assess the severity of lattice distortion, decrease from 0.872 (y = 0) to 0.831 (y = 0.1). The microstructural characteristics of the samples were analysed using a field-emission scanning electron microscope (FESEM). The morphology results reveal that a rise in the amount of V leads stimulates the grain growth in the sample, as evidenced by the increase in grain size from 2.17 µm (y = 0) to 3.71 µm (y = 0.1). The Fourier transform infrared (FTIR) analysis revealed an absorption range of 500 – 600 cm-1, which is indicative of the Mn–O bond deformation vibration. This observation suggests the presence of a MnO 6 bond in the sample. The Tauc plots derived from the UV-Vis spectroscopy data reveal a notable increase in the optical bandgap (E opt) as the concentration of V increases. Specifically, the E opt values rise from 1.71 eV (y = 0) to 2.30 eV (y = 0.1), falling within the range typically observed for semiconductor materials. A distinct metal-insulator transition was observed in all of the samples, exhibiting a range of T MI values ranging from 250 K to 292 K. The scattering model was employed to determine the itinerant e g behaviour in the low temperature region, whilst the SPH model was used to explore the conduction behaviour in the high temperature region. The magnetic characteristic of the samples was investigated using the Alternating Current Susceptibility (ACS) and Vibrating Sample Magnetometer (VSM) techniques, which confirms the existence of a shift in phase from ferromagnetic (FM) to paramagnetic (PM). The T C value exhibits a declining trend from 298.8 K (y = 0) to 274.8 K (y = 0.1). [Display omitted] • The La 0.7 Pb 0.3 Mn 1−y V y O 3 (y = 0 – 0.1) samples crystallized in Rhombohedral structure with a space-group of R-3c. • Modification in metal-insulator transition as T MI values decrease from 292 K (y = 0) to 250 K (y = 0.1) • T C value indicate a decreasing pattern as the V concentration increases, from 298.8 K (y = 0) to 274.8 K (y = 0.1) [ABSTRACT FROM AUTHOR]

In this paper, Ce–Ho–Tb co–doped Bi 2 O 3 compositions were developed using the solid–state reaction method under atmospheric conditions. The XRD patterns confirm the stability of the cubic δ–phase in Ho and Tb–rich compositions but not in the Ce–rich ones, which consist of mixed phases, such as α and β. Peak shifting is additionally apparent in the magnified XRD diagram of primary peaks regarding the (111) diffraction plane, suggesting that the structural features change with doping. At 700 °C, the highest conductivity is found to be 0.30 S/cm for the composition 8Ce4Ho4Tb, and it is comparable to the single–doped (Bi 2 O 3) 0.80 (Er 2 O 3) 0.20 system at the same temperature. The FE–SEM images show the aggregation, particularly in images of Ce–rich compositions, implying that large cations have difficulty penetrating the lattice. The porosity over the surface is dense, particularly for Tb–rich compositions, indicating a decline in conductivity with doping. The cubic δ–phase of Bi 2 O 3 crystal, an excellent ion conductor, is capable of being stabilized at room temperature in Ho-rich compositions. Arrhenius plots of conductivity clearly show that the content ratios of 1:2:1, which is a specific ratio, play a key role in achieving the highest conductivity stable Bi 2 O 3 electrolytes. [Display omitted] • A high ion conductor, δ-Bi 2 O 3 phase was effectively stabilized in Ho and Tb-rich compositions. • The highest conductivity was determined to be 0.30 S/cm, which is greater than 20ESB electrolyte. • In several compositions, the order-disorder transition on the Arrhenius plots is noticeable. • The FE-SEM pictures revealed a local aggregation on the surface, particularly in the Ce-rich specimens. [ABSTRACT FROM AUTHOR]

Glass ceramic was produced by replacing the major glass forming materials, silica and calcium oxide, with derivates from rice husk and periwinkle shells respectively. Glass formulation comprising of silica extracted from the rice husk and calcium oxide from powdered calcined periwinkle shells were compounded with analytical grade sodium carbonate. Silica was extracted from rice husk and characterized using XRD. SEM/EDS of the periwinkle shell revealed a structure dominated by calcium and oxygen; however, there was a significant presence of magnesium. Glass ceramic was produced by melting the mixture at 1300 °C followed by melt quenching. FTIR of the material showed the presence of the carbonyl functional group, calcium oxide, magnesium oxide and various bond configurations of silica. SEM of the glass ceramic showed sparsely distributed particles of the crystalline phase, while XRD revealed the presence of 55% amorphous phase. Several crystalline phases were present, dominated by polymorphs of silica such as quartz (22.15 wt.%) and cristobalite (5.68 wt.%). Also present are mullite (5.58 wt.%), calcite (1.95 wt.%) and Wollastonite (6.86 wt.%). Noticeable in the crystalline phase is Whitlockite (2.33 wt.%), a magnesium and phosphorus rich animal-source bio ceramic, traceable to the periwinkle which may impart some bioactivity to the material. [ABSTRACT FROM AUTHOR]

The structural and electrical characteristics of (Mg, Zn)O ceramics produced using the solid state reaction at 1100 °C for 3 hours were studied applying X-ray diffraction and IR reflection spectroscopy as well as means of direct current measurements versus MgO content in initial charge (varied from 0 to 100 mol.%). It has been shown that electrical conductivity extracted from the IR reflection spectra corresponds to that of hexagonal phase in a solid solution, while plasmon in cubic phase was not observed. The electron concentration in the hexagonal grains of solid solution prepared with MgO content below 30 mol. % in the charge was found to be close to that of ZnO grains. It shows the tendency to decrease with further growth of the MgO content, which was explained by extraction of zinc interstitials, responsible for ZnO conductivity, from ZnO under formation of the MgZnO cubic phase. The direct current measurements have shown the lower conductivity as compared to the value estimated from IR reflection spectra. This fact along with the superlinearity of current-voltage characteristics has been explained by the presence of intergranular barriers, which does not allow obtaining information on the concentration of free electrons in the grain by this method. The possible nature of intergranular barriers as well as the role of grain boundaries in the DC conductivity of samples has been discussed. [ABSTRACT FROM AUTHOR]

This paper presents the ferroelectric and dielectric properties of five-layer Aurivillius oxides (BaBiTiO, PbBiTiO and SrBiTiO) prepared by a solution combustion route with glycine as a fuel at low calcination temperature. The phase formation of these materials with pseudo-tetragonal structure was achieved after calcination at 750°C for 3 h; as confirmed by X-ray diffraction studies. Scanning electron microscopy of the sintered ceramics shows that the grains exhibit a plate-like morphology. The ferroelectric to paraelectric transition temperature ( T ) for Ba-, Pb- and Sr-based bismuth titanate ceramics was found to be 350, 280 and 260°C, respectively. All three materials show multiple relaxation phenomena and their electrical conductivity was found to be temperature dependent. The PbBiTiO ceramic possessed the highest value of activation energy (0.68 eV) and hence shows better ferroelectric properties, as compared to barium and strontium bismuth titanates. [ABSTRACT FROM AUTHOR]

The effects of substitution of Bi by Sn in Bi 2-xSn xSr 2CaCu 2O 8+δ with $(x = 0-0.05)$ on the structural and physical properties were investigated in this paper. The samples were obtained by a solid-state reaction method and pressed uniaxially under 225 MPa before the last heat treatment. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), and electron dispersive X-ray (EDX). XRD studies indicated that all prepared samples were single phase with a small fraction of Bi 2Sr 2CuO 6+δ secondary phase. The lattice parameters of the Bi-2212 and Bi(Sn)-2212 phases were identified using DicVol04 software by [Boultif et al.] The elemental compositions analysis, which was determined from EDX, indicated that the Sn introduced into the microstructure of Bi-2212 phase. The SEM micrographs show that the undoped sample consists of grains well connected with a random distribution. A very different microstructure is obtained for the doped samples, where the grains are more connected with a flat shape characteristic of the Bi-based superconductors. DC magnetic measurements show that the onset transition temperature, of about 81 K for the undoped sample, increases until about 86.2 K for the doped sample. [ABSTRACT FROM PUBLISHER]

Copyright of Archives of Metallurgy & Materials is the property of Polish Academy of Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the paper, the phase composition, sintering behavior and microwave dielectric properties of CaMg 1- x Mn x Si 2 O 6 were investigated via X-ray diffraction, SEM techniques and infrared spectra. Dense ceramic with the lowest porosity was obtained at x = 0.02 when sintered at 1300 °C. Densification had great impacts on the developments of both ε r and Q × f. The variation in τ f was responsible for [MgO 6 ] octahedron distortion and the existence of a secondary phase. Furthermore, the major contributions to the intrinsic dielectric properties were calculated via infrared reflectivity spectra fitting. [ABSTRACT FROM AUTHOR]

Membrane fouling is a key factor limiting the application of a membrane bioreactor (MBR), and membrane-surface modification holds the potential to control membrane fouling and solves this problem. In the research, novel nanocomposite membranes were designed and fabricated using antimicrobial copper nanoparticles (CuNPs) coupled with powdered active carbon (PAC) to mitigate membrane fouling. The successful coating was confirmed by SEM, XRD, and FTIR analysis. Compared with a pristine membrane, the functionalization of CuNPs and PAC improved the hydrophilicity of the modified membrane but led to a lower permeate flux. The result of antimicrobial adhesion experiments showed that the modified M-CuOC displayed high antibacterial activity with the bacteria count decreased by 72%. In MBR operation, the modified M-CuOC leads to the removal efficiency of chemical oxygen demand (COD) increasing to 93%, with better filtration performance under a lower TMP rise. The fouling-resistance analysis demonstrated that, although the intrinsic membrane resistance of modified M-CuOC slightly increased, the reversible and irreversible fouling resistances obviously decreased by 45% and 90%. Moreover, the membrane flux recovery efficiency of the modified M-CuOC also increased by 35%. Overall, these results indicated that, in addition to an improvement in antifouling performance, the functionalization of CuNPs and PAC also enhanced the membrane flux recovery efficiency, revealing a good antifouling potential in a practical application. [ABSTRACT FROM AUTHOR]

Barium titanate powders of ~ 50 nm size were pre-synthesized using a hydrothermal technique to lower sintering and calcination temperatures of (1-x)BaTiO3–xLi0.5Bi0.5TiO3 solid solutions. The obtained powders of the solid solutions were analyzed using TEM and X-ray powder diffraction spectroscopy to indicate their properties. The Rietveld analysis was used to confirm the formation of ferroelectric tetragonal single-phase (1-x)BaTiO3–xLi0.5Bi0.5TiO3 solid solutions. The effects of varying concentrations of Li0.5Bi0.5TiO3 on the structure and dielectric properties were investigated. The unit cell volume decreased with increasing Li and Bi concentration due to the smaller ionic radius of lithium compared to barium. Increasing lithium concentration caused the phase transition in barium titanate to blur, and a liquid phase formed at the grain boundaries, significantly reducing the sintering temperature. Increasing Li and Bi concentration led to a decrease in sintering temperature from 1240 °C (at x = 0.05) to 1100 °C (at x = 0.5). [ABSTRACT FROM AUTHOR]

Copyright of Materials Science / Medziagotyra is the property of Kaunas University of Technology, represented by Prof. Rymantas Jonas Kazys and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Our paper studies the mineralogical and petrographical characteristics of 28 ceramic fragments that were excavated in the village of Palatca, Transylvania (Romania). Optical microscopy, X-Ray powder diffraction (XRD), scanning electron microscopy (SEM), grain size analyses, and porosity measurements were used to investigate the samples. Our objective was to describe or reconstruct the corresponding products and to elucidate the manufacturing process, the firing techniques, and the transformation pathways. Based on our results, we conclude that the Late Bronze Age ceramics (1600-1300 BC) were produced from clay and temper material such as river sand and ceramoclasts. It has been modeled by hand and fired between 800 and 950°C. For most samples, we can narrow the temperature range to 850-900°C. We interpret the data further from a geoarchaeological point of view with respect to the historical evolution of the local culture. [ABSTRACT FROM AUTHOR]

Cracking is generally regarded as an unavoidable consequence of martensitic transformation in polycrystalline ZrO 2 -based ceramics. This shortcoming has limited ZrO 2 -based shape-memory ceramics (SMCs) to micron-sized single- or oligo-crystals to reduce bulk transformation stresses. In this paper we explore an alternate approach to reduce transformation-induced cracking by manipulating the crystallographic phase compatibility in polycrystalline ZrO 2 -CeO 2 ceramics. For a range of compositions 12.5–15 mol% CeO 2 , we present lattice parameter measurements for the tetragonal and monoclinic phases from in situ X-ray diffraction, direct observation of lattice correspondences by electron backscatter diffraction, and calculations of interface and bulk compatibility. We identify ZrO 2 -13.5 mol% CeO 2 as having preferred interface compatibility in that it closely meets the crystallographic cofactor conditions. This composition resists cracking through 10 thermal cycles, whereas other compositions all crack. These results suggest that interface compatibility may contribute more strongly to transformation-induced cracking in ZrO 2 -based SMCs than previously believed and opens a strategy for designing crack-resistant polycrystalline SMCs. Image 1 [ABSTRACT FROM AUTHOR]

Transition metal ions are usually incorporated as chromophores into pyrochlore structures in order to develop colored compounds. However, due to the high toxicity of some of them (Cr, Ni, Co, Cd ...), other nontoxic species such as lanthanide ions have been studied in order to produce environment-friendly pigments. This paper describes the structural and spectroscopic study of a pink pigment based on the Er2Ti2− xZr xO7 system synthesized by a sol–gel route. A previous research on the Er2Ti2O7 system revealed that this compound exhibits a pink coloration only in its defect fluorite-type structure. At high temperature (800°C), an atomic rearrangement into a pyrochlore network significantly reduces its coloration. The stabilization of the fluorite phase in Er2Ti2O7 through substitution of Ti(IV) with larger Zr(IV) ions is studied in this work. The analysis by differential thermal analysis and thermogravimetric analysis, X-ray powder diffraction, and Raman techniques indicates that the introduction of Zr(IV) species successfully avoids the undesired fluorite-to-pyrochlore transition. The colorimetric study concludes that the optimal composition corresponds to the Er2Ti0.6Zr1.4O7 stoichiometry, which gives an intense pink coloration independently of the thermal treatment. This study introduces a novel nontoxic pigment suitable for industrial applications at both low- and high-temperature ceramic technologies. [ABSTRACT FROM AUTHOR]

Diffraction provides an effective means to characterize ferroelectric materials under the application of dynamic and cyclic electric fields. This paper describes a typical time-resolved diffraction setup at a synchrotron facility using high X-ray energies. Such as a setup is capable of measuring the structural response of ferroelectric ceramics to electric fields of various frequencies, amplitudes, and waveforms. The use of high energies also allows the response of the sample to be measured at various angles to the applied load. The results of 3 different types of electric loading are presented and discussed: the structural response of ferroelectric ceramics to a single electric field step function, a cyclic electric field of square waveform, and a cyclic electric field of sinusoidal waveform. Each type of electric field loading provides unique information about the material behavior. [ABSTRACT FROM AUTHOR]