Fine Ceramics Research Articles

Application of Solid-state Electrochemical Analysis in Ancient Ceramic Identification and Characterization: A Review

Background: Ceramics can reflect ancient technology and art, therefore, it has a very important position in archaeology. However, it is far from enough just to study the shape of pottery and porcelain. It is necessary to use advanced scientific and technological means to conduct a comprehensive analysis of pottery and porcelain, so as to study the information hidden deep in the remains of ceramic objects. Methods: The solid voltammetric method can be used to obtain information about the composition of materials used in ancient ceramics. This new method can be applied to insoluble solids for example, providing qualitative and quantitative information and structural information with little soluble solids. The method requires only ng-μg sample. Results: In this review, we first describe the development of solid-state voltammetric method and our work in this field. Then, we describe in detail the application of this method in archaeology, especially in the analysis of ceramics. Finally, we describe the analytical applications of other electrochemical techniques for ceramics analysis. Conclusion: Due to the low demand for samples and the high-cost performance of analytical instruments, this method has been widely studied in Europe. To sum up, we propose to establish a microsampling method for ancient ceramics. A new method for the protection of fine ancient ceramics by the suitable carrier and the fixation on the surface of the electrode. These improvements can enable solid-state electroanalytical chemistry technology to achieve more comprehensive and accurate quantitative analysis of ancient ceramics particles. We also propose the current challenges and future directions of solid-state electroanalytical chemistry.

Finite element analysis of fracture behavior in ceramics: Prediction of strength distribution using microstructural features

AbstractThe estimation of the strength scatter caused by internal defects is necessary in analyzing a reliable design of advanced ceramic components. In this study, we proposed a finite element analysis methodology to predict the stochastic fracture behavior of ceramics based on the microstructural features obtained by the scanning electron microscopy and X‐ray computed tomography. Here, the two‐ and three‐dimensional distribution microstructural data are approximated by various probability density functions and are reflected in the dispersion of parameters of the damage model via a fracture mechanics model. We then applied the proposed method to alumina fine ceramics sintered at three different temperatures, and performed the three‐point bending test. Furthermore, the numerically created Weibull distributions were compared with those obtained experimentally. Our analysis results confirm that the proposed method can reasonably predict the strength scatter in ceramics.

Solution combustion assisted synthesis of ultra-magnetically soft LiZnTiMn ferrite ceramics

Wide practical application and increasing functional requirements for high-frequency ceramics lead to the active search for novel multicomponent ferrites and their synthesis technique. In this paper, a solution-combustion-assisted approach was proposed and realized for the successful production of ultra-magnetically soft LiZnTiMn-ferrite ceramics with advanced electromagnetic performance. Preceramic nanopowders of Li0.28Zn0.16Ti0.41Mn0.10Fe2.05O4 with spinel structure were synthesized via glycine-nitrate combustion at variable Ox/Red ratios (φ = 0.5, 1.0 and 1.5) followed by stabilizing quenching (600 °C, 2 h) and vibrating mill grinding. LiZnTiMn-ferrite-based fine ceramics were produced then using PVA binding (1 wt%), isostatic pressing (400 МPа) and Bi2O3-assisted (0.3 wt%) isothermal sintering (980 °C, 8 h) techniques. As result, a series of LiZnTiMn-ferrite ceramic samples were obtained and their structure was examined in detail using XRD, SEM, EDXS, AAS and ASA methods. It was shown that the Ox/Red ratio of the initial reaction solution is an efficient parameter affecting both crystallite size (26–38 nm) /crystallinity degree (up to 91%) of preceramic LiZnTiMn-ferrite powders and grain size (2.7–9.8 µm) / grain size distribution of resulting fine ceramics. Based on the results of vibration magnetometry it was found that ceramics samples possess the ultra-magnetically soft behavior with Hc = 0.61–0.89 Oe, Mr = 3.62–5.13 emu/g and Ms = 67.23–78.70 emu/g depending on the initial Ox/Red ratio. Besides, results of resonator analysis (100 Hz - 1000 kHz) demonstrate that the dielectric constant of the samples strongly depends on the average grain size and reaches its maximum value (~ 6.4⸱10–4) at 100 Hz for the stoichiometric Ox/Red ratio (φ = 1.0) of reagents, wherein the linewidths of ferromagnetic resonance and resonance of spin waves practically unchanged and are in ranges of 327–344 and 1.43–1.45 Oe, respectively. Thus, it was found that the solution combustion synthesis, adapted for fine ceramics production, provides controlling morphological and structural parameters of the pre-ceramic powders through Ox/Red ratio of initial reagents and as consequence, allows variable magnetic and dielectric characteristics of the resulting ceramic products. Developed ceramic materials can be promising for use as a basis for modern radio-electronic devices of both civil and military use.

Muscovite and ceramic pegmatite dumps in the Arctic regions of Karelia as a potential raw material for industrial use

mining enterprises in the Loukhsky region of the Republic of Karelia, rated as one of the Arctic regions of the Russian Federation. The purpose of this study was to establish the rock composition of the dumps and identify the possibility of their use in various industries. It has been found that pegmatite dumps are mainly represented by quartz, microcline and plagioclase pegmatite, micas (muscovite, intergrowths of muscovite with biotite), overburden and host rocks (gneisses, gneiss granites, amphibolites, and gabbro). Quartz raw materials may be used to produce silicon carbide, as well as in the glass industry, in fine ceramics, welding consumables, silica refractory products, and investment casting. Plagioclase concentrate may be used to obtain low-temperature porcelain and coarse crushed plagioclase for the glass industry. Fine and crushed muscovite is used as a filler in the rubber industry, for coating arc welding electrodes, in the manufacture of paints and varnishes, plastics, paper, titaniummica pigments, and composite materials. The host rocks may be used to produce crushed stone. After proper additional processing, lump ceramic raw materials from the dumps of ceramic pegmatites may be used to obtain fine and construction-grade ceramics and in the glass industry. Pegmatite processing waste is suitable for the manufacture of decorative crushed stone and crushed stone for filling secondary roads. Further processing and subsequent use of pegmatite dumps allows organizing environmentally friendly mining operations and preserving the resource potential of the subsoil.The research was conducted under the financial support from the federal budget for the fulfillment of the state assignment set for the Karelian Research Center of the Russian Academy of Sciences (121040600172-1).

Felsite in Ceramic Materials Production

This project is devoted to the study of the felsite properties for the purpose of its application in the production of various types of fine ceramics: ceramic tiles, acid-resistant tiles, aluminosilicate proppants, etc. Felsite is a mixture of quartz (about 40%) and feldspars. In the compositions of ceramic masses, felsite can play the role of both nonplastic due to the quartz content, and flux due to the content of feldspars, that reduces the amount of mixture components. When felsite is fired, the melt appears at a temperature above 950°C. The felsite has a sintering effect when fired at a temperature of 1000°C. Glass phase enriched with SiO2 ensures the absence of material deformation after firing. Also, glassy phase provides high-acid and chemical resistance of materials based on it. In addition, after firing above 1150°C, felsite has a light color, which is a great advantage in comparing it as a melt with other iron-alkali-containing materials. Ceramics based on felsite does not require the use of opacified glazes.

Investigation of unexplored kaolin occurrences in southern Mauritania and preliminary assessment of possible applications

AbstractNon-metallic raw materials are largely unexplored in many African countries. In an attempt to reduce this knowledge gap, kaolin occurrences in three promising regions of southern Mauritania were examined. The aim of the paper is to describe the occurrences and characterize the material in terms of mineralogy and potential technical use in the ceramics industry. The kaolins are geologically associated with various sedimentary rock units in either the Coastal Basin (Kaédi), the Mauritanide Belt (Hassi Abyad) or the Taoudeni Basin (Néma). Geochemical data show Al2O3contents of between 9% and 38% (corresponding to 23–96% kaolinite). Samples from the Hassi Abyad and Kaédi regions have greater kaolinite contents on average and were further investigated mineralogically. The kaolin from the Néma region contained less kaolinite (<50 mass%). The region is also less accessible and hence is not considered further in this study. X-ray diffraction, X-ray fluorescence and infrared spectroscopy confirmed the geochemically calculated kaolinite contents of the kaolins and identified quartz, anatase and goethite as the remaining major mineral constituents. The degree of structural disorder of the kaolinites (determined by infrared spectroscopy) is generally greater in the Kaédi occurrences than at Hassi Abyad. Ceramic tests proved that all of these kaolin raw materials might be used for the production of ceramics, and some may even be used for fine ceramics. From an economic point of view, the Hassi Abyad deposit is interesting in terms of its quality and reserves, aspects that will be addressed in detail in a follow-up study.

Production Method of Zirconia Powder for Fine Ceramics

Y2O3-stabilized ZrO2 (YSZ) ceramics have been used for various engineering applications or as a solid electrolyte in oxygen sensors and fuel cells. The performance in YSZ strongly depends on the microstructure which is directly determined by the characteristic of raw powder. In this paper, the synthetic methods of YSZ powder and its starting material are first overviewed, and then the formation mechanism of YSZ powder is explained, focusing the hydrolysis process which is industrially adopted. Next, microstructural development during sintering of the hydrolytic YSZ powder is summarized, focusing Y2O3-stabilized tetragonal ZrO2 polycrystal (Y-TZP) with excellent mechanical properties among YSZ. The author finally introduces that based on the hydrolytic process technique and microstructural knowledge, low temperature degradation that is fatal shortcoming of Y-TZP can be resolved by controlling the grain-boundary nanostructure and chemical composition distribution in Y-TZP.

Evaluation of Rate of Adhesion of Lactobacillus namurensis Strain GYP-74 to Porous Fine Ceramics

This study aimed to evaluate the ratio of adherence of lactic acid bacteria (LAB) to porous fine ceramics in order to develop a novel LAB-rich pickle container for the production of functional fermented vegetables. Some LAB were isolated from the salted rice bran used for pickling (Nukadoko in Japanese). These isolates were classified in Lactobacillus namurensis by phylogenetic analysis. Some pottery-shard (PS) samples were prepared by varying the mixing rate of polyacetal (POM) resin to clay (0–30% (v/v)) and the burning temperature (1000 °C or 1100 °C). A test of the adherence of strain GYP-74 to the PSs was performed. The results showed that the adherence rate was significantly higher in the PSs burned at 1100 °C as compared with those burned at 1000 °C. A pore distribution analysis showed that pore sizes of less than a few µm and pore sizes in the range of a few µm to a few hundred µm were mainly distributed in the PSs without and with POM, respectively. X-ray diffraction analysis showed that both PSs with and without POM contained quartz and hematite. The PSs burned at 1000 °C and 1100 °C specifically contained microcline and mullite, respectively. This study revealed the basal information regarding what makes PSs adequate for LAB adhesion.

The Aksumite site of Wakarida in the region of Tigrai, Ethiopia: first results of archaeological investigations

The site of Wakarida is situated near the eastern edge of the Tigray plateau, dominating the Afar depression. The study on the site has started in 2011 with a short archaeological and geophysical survey. During the three campaigns of excavations between 2012 and in 2013, carried out in two areas, the archaeologists unearthed typically Aksumite buildings accompanied by abundant ceramic material, with a significant proportion of fine ceramics. The buildings have been dated between the 3rd and the 6th century AD, period confirmed by C14 analyses. In several places, the remains of walls visible on surface and pottery shards testify to the existence of other ancient structures. The site of Wakarida, covering some 9 ha, was probably a small city or a village during the Aksumite period. The survey of its region has enabled to study the landscape, mostly shaped by man, and to discover other archaeological sites, two of which are comparable in size to Wakarida.

Obtaining and Characterizing Phosphatic Porcelain

The research aimed to obtain phosphate porcelain, by using the ash resulting from burning bones from meat processing plants. The applied processing technology allows obtaining fine ceramics at lower temperatures than the one used in the case of feldspar porcelain, having as effect the increase of the durability of the firing furnaces and the realization of the products at lower production costs. Five series of phosphate porcelain samples were performed in laboratory conditions, with different compositions, by firing at a temperature of 1250 ℃, temperatures lower than those necessary for the firing of feldspar porcelain of 1350-1450 ℃. The porosity and density of the samples were determined and the microstructural analysis of the materials made in the five research variants was made.

Inca Human Sacrifices on Misti Volcano (Peru)

One of the most impressive examples of an Incacapacochaceremony was discovered during an archaeological expedition to the summit of Misti volcano in 1998. The offerings at the site included several human sacrifices, along with fine ceramics and figurines made from gold, silver, andSpondylussp. shell. One of the two burials appeared to contain the bones of males and the other of females. The sex was established based on the contents of the graves, because the fragile skeletal material had been badly affected by volcanic activity and exact identification was difficult to make in situ. To limit the risk of damage, the bones were excavated together with the surrounding soil and transported in frozen blocks to the Museo Santuarios Andinos of Universidad Católica de Santa María in Arequipa. This material was the object of a bioarchaeological investigation in February and March 2018. The results revealed that at least eight individuals had been buried in the graves. The findings have increased our understanding of the age categories and physical condition of the individuals chosen to be sacrificed during thecapacocharitual.

Physical, strength, and microscale properties of plastic fiber-reinforced concrete containing fine ceramics particles

The use of recycled ceramic and plastic waste in civil engineering applications, such as developing engineered composites, is a promising waste management technique than landfilling. This experimental study investigates the engineering properties of concrete made with ceramic tile wastes as fine aggregates and Polyethylene terephthalate (PET) bottles as fibers. Ceramic waste (CW) was utilized in different ratios of 50% and 100% replacing the fine aggregate weight. Plastic fibers were added in ratios of 1.5% and 2.5% by weight of concrete. The engineering properties considered include the fresh state, mechanical, and water absorption. The microscale and mineralogy properties of the composite were determined using scanning electron microscopy and X-ray diffractometer, respectively. The result showed that incorporating plastic fibers and ceramic waste resulted in a decrease in the slump value, hence a reduction in the workability of the fresh concrete. The concrete sample with 100% fine ceramics aggregates and 2.5% plastic fibers achieved the highest compressive strength. The tensile strength increased with increasing curing age. Overall, the tensile strength of the concrete was increased by as high as 45% by the inclusion of 100% fine ceramics aggregates and 2.5% plastic fibers. The water absorption of the concrete decreased with increasing content of ceramics and plastic fiber.

The high temperature reaction of ammonia with carbon and SiC–C ceramics

This contribution aimed at developing a treatment under ammonia in order to eliminate free carbon from the surface of SiC-based fine ceramics like fibers or coatings. The reaction of NH3 with graphitic and non-graphitic carbon was first investigated through kinetic measurements, in situ gas phase analysis and physicochemical investigations of the solid. The carbon etching rate is controlled by heterogeneous reactions involving active sites arising from bulk structural defects and the formation of HCN. A selection of SiC-based fibers and coatings with various carbon contents and (micro)structures was treated in ammonia in favorable conditions. The analyses of the tested SiC–C specimens revealed a reduction of the free carbon content and, simultaneously, a nitridation of the initial Si–C–(O) continuum over a reaction layer. The growth rate, composition and the volume change of this layer vary with the initial microstructure. The ammonia treatment is able to restore the adhesion of carbon-contaminated surfaces.

HIGH-SILICA ROCKS OF CENTRAL KARELIA – A POTENTIAL SOURCE OF QUARTZ RAW MATERIAL

The results of mineralogical-technological study of high-silica rocks of Central Karelia are discussed with a view to assessing the potential of using these rocks as natural material for producing quartz concentrates for various applications. Weakly transparent vein quartz, pebble quartz from Paleoproterozoic conglomerates and volcanogene-sedimentary silicites were subjected to optical and electron microscopy, microprobe analysis, X-ray fluorescence and diffraction analysis, atomic emission spectrometry. Technological studies of the silicites showed they can be enriched to produce quartz-feldspatic concentrate meeting the requirements to feedstock for fine ceramics (Fe2O3 ≤ 0.2 %, K2O+Na2O ≥ 8 %, K2O/Na2O = 2). Owing to low Li, B and P content, quartz concentrates made from pebble quartz conglomerates fulfill the requirements for raw material for highgrade ferrosilicon production. Processing experiments were carried out, showing that the quartz concentrate of the –0.315 + 0.1 mm fraction obtained from weakly transparent vein quarts, with 34.6 ppm total impurity content meets the requirements for high purity quartz products of some grades (TU 5726‑002‑11496665‑97) and is suited for extra pure fused glass utilizable in the manufacturing of semiconductor materials, electronics, lighting engineering, means of fiber-optic communication.

Modelling and experimental investigation of pore-like flaw-strength response in structural ceramics

Although important, fracture strength in structural ceramics remains difficult to predict due to the inherent micropores, and there is a tremendous need for more precise modelling of pore-like flaw-strength relationship. In this study, classical crack problems were successfully transformed into pore-like flaw-strength models by adding a reasonable stress correction factor proposed by Gomez. Based on the accurate fracture toughness measurement and the precise laser introduction of flaws vs strength tests, the optimized Sato-Takahashi model, which is suitable for any cross-sectional shapes and sharpness flaws, was found to have fairly good prediction for fracture strength in five typical structural ceramics. The experimental error at very small-sized flaws was analyzed from the aspects of the critical flaw size and the inherent flaw size detected by nano-CT. Overall, the simple and user-friendly optimized Sato-Takahashi model could pave the way for quantitative assessments of reliability and failure causes for fine ceramics.

Fine Ceramics for New Space

Fine Ceramics for New Space

Determination of the Compressive Strength of Concrete from Binary Cement and Ternary Aggregates

One of the most active fields of research embraced by many disciplines, including civil engineering, is material reuse. It is known that ceramics wastes from various construction and demolition sites and manufacturing processes are dumped away into the environment, resulting in the pollution that threatens both agriculture and public health. Therefore, the utilization of ceramic waste in construction industries would help to protect the environment from such pollutions. This paper presents the results of an experimental analysis of the effects of partial replacement of coarse aggregates, fine aggregates, and ordinary Portland cement with the ceramic waste, at percentage levels of 0%, 5%, 10%, and 20%; and the assessment of the strength property of the concrete produced with optimum combination of the constituents. Compressive strengths of this concrete were determined at 7, 28, and 56 days of curing using 150 × 150 × 150 mm cube specimens. Test results showed that the compressive strength of the concrete decreased as the content of ceramic waste present in the concrete increased. Thus, concrete produced from the partial replacement of ordinary Portland cement with ground ceramics gave compressive strengths of 16.6 N/mm2 and 13.4 N/mm2 at 5% and 20% replacement levels respectively. Similarly, the compressive strengths of concrete from the partial replacement of sand with fine ceramics were 13.8 N/mm2 and 10.9 N/mm2 for 5% and 20% replacements respectively. For 5% and 20% replacement levels of granite with crushed ceramics in concrete gave a compressive strength of 11.6 N/mm2 and 9.7 N/mm2, respectively. For concrete derived from the partial replacement of stone dust with fine ceramics, the compressive strengths were 19.6 N/mm2 and 18.10 N/mm2 respectively for 5% and 20%. For concrete produced from the partial replacement of bush gravel with crushed ceramics, the compressive strengths obtained were 10.9 N/mm2 and 8.98 N/mm2 respectively for 5% and 20% replacements. Finally, the concrete derived from the optimal combination of binary cement, ternary fine, and coarse aggregate had a compressive strength of 22.20 N/mm2 which is higher than the compressive strength of the control mixture at 18.10 N/mm2. The result of the ANOVA carried out showed that the compressive strength obtained for each partial replacement of different components is statistically significant at 5%, i.e. the change in the compressive strength of the concrete produced is due to the presence of ceramic waste.

Bruce Yonemoto: Made in Occupied Japan

Bruce YonemotoMade in Occupied Japan Rika Hiro (bio) Click for larger view View full resolution Bruce Yonemoto (1949–) Made in Occupied Japan (Sakasama Makasa), 1998. Ceramic mug and metal base 7 ½ x 8 ⅜ x 4 ¾ in. (19.05 x 21.27 x 12.07 cm.). The Museum of Contemporary Art, Los Angeles, Gift of Barbara Wise. © Bruce Yonemoto, Image courtesy of the artist. [End Page 162] Conceptual and multimedia artist Bruce Yonemoto's (b. 1949) display of a group of mugs, cup-and-saucer sets, and porcelain figurines provokes a sense of bewilderment. Each object is colorful, charming, nostalgic, and even kitschy. However, the artist curiously places them upside down to highlight their trademarks and country of origin, "Made in Occupied Japan," which forms the title of the series that he initiated in 1998. "Made in Japan" has become a talisman of good quality, refined craftwork, and tasteful design. Yet it once meant the opposite—inexpensive and sometimes defective goods in the immediate postwar period.1 In the 1930s and 40s, Japanese fine but low-cost ceramics were seen as a threat to American pottery manufacturers.2 "Made in Occupied Japan," in contrast, suggests a narrow range of production dates and circulation limited to Europe and especially North America. Under General Douglas MacArthur, the Supreme Commander of Allied Powers (SCAP), the Occupation of Japan lasted from September 1945 until the conclusion of the Treaty of Peace in April 1952. However, it was only in the single year of 1947 that the mark of "Made in Occupied Japan" or "Occupied Japan" was required for virtually all export items, including toys, textiles, cameras, and porcelain.3 Although the mark became non-compulsory in 1949, Japanese manufacturers continued the practice of adding this imprint until the end of the Occupation Period.4 This historical imprinting intersects with the biography of Yonemoto himself, whose identity was, to some extent, trapped between Occupied Japan and liberating America. The sansei artist was born to ex-interned Japanese American parents in 1949. He studied at the University of California, Berkeley, where he was exposed to the rise of Asian American and Third World studies, and decided to further pursue art and his cultural roots in Japan.5 Since then, Yonemoto has been questioning the authenticity of histories and memories as well as complicated gender, cultural, racial, and/or ethnic representations through his works. His multimedia installations frequently involve [End Page 163] complex structures to allow such a nuanced reading of memories and the politics of representations. For example, a 1995 video installation, Parana, utilizes a coffee porcelain set made in Paraná, Brazil, with hand-painted oval images featuring Oscar Niemeyer's modernist architecture in Brasilia. Yonemoto superimposes found film footage of Paraná's Japanese Brazilian community gathering over one of Niemeyer's designs. Compared to Parana and Yonemoto's other installations, Made in Occupied Japan seems fairly simple and straightforward. This 1998 example of a "Made in Occupied Japan" work consists of a single Toby mug in the shape of MacArthur's head and is stamped "MERIT OCCUPIED JAPAN." MacArthur wears his iconic Philippine Field Marshal cap, but unlike other comical Toby mugs, his face looks serious and reveals signs of his aging, such as saggy cheeks and under-eye bags. A toughness and energy issue forth from his cherry-colored lips and wide-open eyes. In the domestic space of America at the time of the mug's creation, it would have functioned as a memento of America's strength, its victory over Japan, and MacArthur as the executor of postwar democracy during the rise of communism. By changing the mug's orientation, however, and placing it upside down, Yonemoto playfully challenges the above, referencing Duchamp's readymades. The mug in Yonemoto's presentation instead becomes a keepsake of the hypocrisy of American democracy, which incarcerated nearly 120,000 Americans of Japanese ancestry, about two-thirds of whom were American citizens and included Yonemoto's family. [End Page 164] Rika Hiro Rika Hiro is a Visiting Assistant Professor, Occidental College, California. Her doctoral dissertation looked at the aftereffects of the atomic bombs in arts and exhibition culture in postwar Japan. She co-founded the non...

La cultura morisca y su importancia en el desarrollo de Argelia en el siglo XVII

En la Argelia del siglo XVII, la agricultura tomó una nueva cara con los productos nuevos que trajeron con ellos los moriscos expulsados de España tras la Reconquista. Esos llegaron con nuevas formas de trabajar la tierra y con técnicas de riego muy útiles para una buena higiene de vida no sólo para los humanos, sino también para las plantas lo que muestra que los moriscos se aplicaron en todos los niveles de la economía urbana y suburbana. La artesanía tuvo, a su vez, un papel muy importante en las grandes urbes del Magreb central. Los artesanos moriscos dominaban las técnicas de las cerámicas finas de Al Ándalus, consideradas productos caros y apreciados. Sus piezas eran aptas para muchos usos, técnica que continuaron aplicando a su llegada a tierras del Magreb Central. Sin embargo, los moriscos destacaron más en el trabajo de la seda, actividad que siguieron desarrollando en sus nuevos destinos, hasta llegar a competir las ciudades argelinas con las españolas en este dominio. Cambiaron totalmente el sentido del comercio en Argel introduciendo nuevos hábitos de compra y venta de productos. Los moriscos se integraron de distintas maneras según las urbes donde se instalaron. En las ciudades del litoral centro magrebí y algunas del interior no muy alejadas del mar, les acogieron muy bien y adoptaron muchas de sus prácticas. Dichas prácticas perduraron y siguen presentes en la sociedad argelina actual sobre todo en ciudades como Tremecén, Mostaganem, Blida, Cherchel, Argel o Bujía.

Dielectric behavior of spark plasma sintered BaTi0.7Zr0.3O3 relaxor ferroelectrics

In the present work we have studied the transport and dielectric behavior of BaTi0.7Zr0.3O3 (BTZ30) relaxor ferroelectrics prepared by spark plasma sintering. Nanocrystalline powder of BTZ30 was obtained by solid state reaction followed by mechanical milling. Fine and coarse-grained ceramics of BTZ30 were prepared by spark plasma sintering at 1100 and 1400 °C, respectively. The obtained materials were characterized by X-ray diffraction and scanning electron microscopy. The grain size of the BTZ30 ceramics increased from 200 nm to 3–5 μm as the sintering temperature was increased from 1100 °C to 1400 °C. The electrical and dielectric properties of BTZ30 ceramics were studied by impedance spectroscopy over −150 to +200 °C temperature range. The dielectric constant exhibits very large values >105 for the spark plasma sintered ceramics associated with very high dielectric loss and electrical conductivity. The insulating nature of the BTZ30 ceramics could be retained by re-oxidation of the samples. The dielectric data of the annealed have been analyzed by the modified Curie-Weiss law and the relaxation process in the materials was fitted by Vogel-Fulcher model.