Calcination

The formation of solid solutions of the type [Ba(HOC2H4OH)4][Ti1−x Gex (OC2H4O)3] as Ba(Ti1−x /Gex )O3 precursors and the phase evolution during thermal decomposition of [Ba(HOC2H4OH)4][Ti0.9Ge0.1(OC2H4O)3] (1) are described herein. The 1,2-ethanediolato complex 1 decomposes above 589 °C to a mixture of BaTiO3 and BaGeO3. A heating rate controlled calcination procedure, up to 730 °C, leads to a nm-sized Ba(Ti0.9/Ge0.1)O3 powder (1a) with a specific surface area of S = 16.9 m2/g, whereas a constant heating rate calcination at 1,000 °C for 2 h yields a powder (1b) of S = 3.0 m2/g. The shrinkage and sintering behaviour of the resulting Ba(Ti0.9/Ge0.1)O3 powder compacts in comparison with nm-sized BaTiO3 powder compacts (2a) has been investigated. A two-step sintering procedure of nm-sized Ba(Ti0.9/Ge0.1)O3 compacts (1a) leads, below 900 °C, to ceramic bodies with a relative density of ≥90%. Furthermore, the cubic ⇆ tetragonal phase transition temperature has been detected by dilatometry, and the temperature dependence of the dielectric constant (relative permittivity) has also been measured.

The diatomaceous earth (DE), collected from the Mariovo region in North Macedonia, was characterized and thermally modified. The material represents a sedimentary rock of biogenic origin, soft solid that can be easily disintegrated, with white to grayish color, with bulk density of 0.51-0.55 g/cm 3 , total porosity of 61-63%, and specific gravity of 2.25 g/cm 3. The chemical composition is as follows: SiO 2, 86.03; Al 2 O 3 , 3.01; Fe 2 O 3 , 2.89; MnO, 0.06; TiO 2, 0.20; CaO, 0.76; MgO, 0.28; K 2 O, 0.69; Na 2 O, 0.19; P 2 O 5 , 0.15; and loss of ignition, 5.66 (wt%). The mineralogy of the raw DE is characterized by the predominant presence of amorphous phase, followed by crystalline quartz, mus-covite, kaolinite, and feldspar. Significant changes in the opal phase are observed in the 1,000-1,200°C temperature region. At 1,100°C, the entire opal underwent solid-solid transition to cristobalite. Further ramp of the temperature (1,100-1,200°C) induced formation of mullite. Scanning electron microscopy (SEM) and transmission electron micro-scopy depict the presence of micro-and nanostructures with pores varying from 260 to 650 nm. SEM analysis further determined morphological changes in terms of the pore diameters shrinkage to 120-250 nm in comparison to the larger pores found in the initial material. The results from this investigation improve the understanding of mechanism of silica phase transition and the relevant phase alterations that took place in DE upon calcination temperatures from 500 to 1,200°C.

The key step in the preparation of mesoporous silica materials is the removal of organic templates occluded inside the pores including nonionic, cationic, anionic surfactants and even ionic liquid (IL). The most common method to remove templates is conventional calcination under air at 550°C. Although templates can be completely removed from the pores, calcination suffers many serious drawbacks including significant framework shrinkage, the collapse of the ordered structure, reduction of silanol concentrations on the pore wall (which are of high importance for postmodification), generation of large amounts of CO 2 and organic amine compounds, the presence of carbon deposits or coke as a contaminant, elimination of organic functionalities (such as organoalkoxysilanes with amino groups), and the inability to recover or reuse expensive organic templates. That is why many attempts have been reported in the literature to develop novel methods for removing organic templates that are favorable from both economic and environmental standpoints for potentially large-scale applications. The current study reviews the recent development methods for template removal from various types of mesoporous silica materials. We have divided the template removal approaches into two categories: physical method and chemical method. The effects of those methods are discussed in detail on the textural and structural properties of mesoporous silica materials along with the template removal mechanism and their pores and coins.

Cadmium substituted cobalt ferrite nanoparticles are synthesis using the chemical method. The as-prepared ferrite nanoparticles are calcinated at 300 °C and 600 °C respectively. The samples are studied using; Powder XRD, SEM with EDX, TEM, FT-IR, TG-DTA and vibrating sample magnetometer (VSM) in order to study the calcination temperature effect on structural, morphological and magnetic properties. The magnetic properties, like saturation magnetization and coercivity increases with increasing the calcination temperature. This enhancement is attributed to the transition from amulti-domain to a single-domain nature. The absorption bands observed at 588 cm À 1 (ν 1) and 440 cm À 1 (ν 2) are attributed to the vibrations of tetrahedral and octahedral complexes. The TG-DTA curves reveal the thermal stability of the prepared ferrite nanoparticles. The calcination temperature influences the magnetic properties, surface morphology and crystalline size.

The syntheses of phase-pure and stoichiometric iron sillenite (Bi25FeO40) powders by a hydrothermal (at ambient pressure) and a combustion-like process are described. Phase-pure samples were obtained in the hydrothermal reaction at 100 °C (1), whereas the combustion-like process leads to pure Bi25FeO40 after calcination at 750 °C for 2 h (2a). The activation energy of the crystallite growth process of hydrothermally synthesized Bi25FeO40 was calculated as 48(9) kJ mol−1. The peritectic point was determined as 797(1) °C. The optical band gaps of the samples are between 2.70(7) eV and 2.81(6) eV. Temperature and field-depending magnetization measurements (5−300 K) show a paramagnetic behaviour with a Curie constant of 55.66×10−6 m3 K mol−1 for sample 1 and C=57.82×10−6 m3 K mol−1 for sample 2a resulting in magnetic moments of µmag=5.95(8) µB mol−1 and µmag=6.07(4) µB mol−1. The influence of amorphous iron-oxide as a result of non-stoichiometric Bi/Fe ratios in hydrothermal syntheses on the magnetic behaviour was additionally investigated.

Five samples of gypsum and one sample of limestone were collected from an outcrop in Qara Chugh Anticline. The samples of gypsum were analyzed chemically before and after calcination. The purity of the samples of gypsum and limestone was calculated and the (H 2 O +) content of the calcined samples of gypsum was determined. The physical and mechanical properties of plaster of Paris produced from calcining the samples of gypsum were tested according to the Iraqi and American Standards. A wallboard sample was made using basic materials according to the American Standard. The chemical analyses of the samples of gypsum and plaster of Paris conform to the Iraqi and American Standards. The Fat'ha Formation rocks in the Makhmur area are suitable for making wallboard. The optimum conditions for calcining the studied gypsum rocks to produce plaster of Paris conforming to the standard specifications and suitable for the manufacture of wallboard are 130 °C for 1 hour.

In recent years, developing economical adsorbents to treat with different types of pollutants has attracted great interest. Mussel shells are abundant in the sea and cause waste. In this study, the uncalcinated and calcinated mussel shells were characterisated for their surface characteristics. Mussel shells washed with tap water and distilled water several times and dried for 12 hours in an oven. Then they were calcined at 900°C for 2 hours. The calcined sample was washed with distilled water and dried at 105°C. And then, the sample was calcined at 400°C with 2°C/min heating rate for 4 hours. The calcined and uncalcined mussel shell samples were characterised by Fourier transformed infrared spectroscopy, scanning electron microscopy equipped with an energy dispersive spectrometer, Brunauer-Emmett-Teller and Zeta potential mesaurements. The results indicated that calcination studies improved the surface charasteristics of the mussel shells and that the calcinated mussel shells can be used in adsorption studies as a low-cost, eco-friendly biosorbent efficiently.

In this study, the effect of calcination temperature and time on the structure of calcinated magnesite was investigated. In addition, the effect of calcinated magnesite on rheology when added into bentonite suspension was also examined. Electrokinetic, rheological and stabilization studies including coagulation and gelation tests were performed to explain the mechanism of viscosity increase in bentonite suspension upon addition of the calcinated products. FTIR, SEM, BET analyses and rheological data were used to determine the transition degree of MgCO3 to MgO, and evaluate the structure of MgO and bentonite suspensions. The results from this study showed that specific surface area (SSA) and mean pore diameter (MPD) values for the calcinated products were directly affected by the calcination temperature and time. According to the ignition loss and transition ratio from MgCO3 to MgO of calcinated samples, it was found that the calcination was completed above 800oC. In order to obtain a bentonite suspension with higher viscosity, the sufficient amount of MgO particles and interaction of these with bentonites particles were found necessary even if median pH and total dissolved ions values were stable. Based on these results, the formation of gelation and heterocoagulation between magnesite and bentonite particles were found to responsible for these.
Keywords: MgCO3, MgO, activation, bentonite, interaction, viscosity

Boron doped PVA/Zr-Al acetate nanofibers were prepared by electrospinning using PVA as a precursor. The effect of calcination temperature on morphology and crystal structure was investigated at 250, 500, and 800 °C. The study also establishes the effect of boron doping on the morphology of PVA/Zr-Al acetate nanofibers at various calcination temperatures. The measurements showed that the conductivity, pH, viscosity and the surface tension of the hybrid polymer solutions have increased with boron doping. In addition, the fibers were characterized by FTIR, DSC, XPS, XRD and SEM techniques. The addition of boron did not only increase the thermal stability of the fibers, but also increased the average fiber diameters, which gave stronger fibers. The DSC results indicated that the melting temperature (Tm) of the fibers was increased from 256 to 270 °C with the addition of boron. XRD peak patterns showed that after further heat treatment at 800 °C, zirconia exists in two phases of tetragonal and monoclinic modifications. Moreover, alumina does not transform into the γ-Al2O3 and θ-Al2O3 phase at 800 °C. The SEM appearance of the fibers showed that the addition of boron resulted in the formation of crosslinked bright surfaced fibers.

Novel nanocomposite adsorbent materials were synthesized by condensation polymerization of TEOS in the presence of saponified guar-graft-poly(acrylonitrile) (SG) as template. The effect of changing the molecular size of SG on the final properties of the composite materials was investigated in this paper. The composites were thermally treated at temperatures ranging from 80 to 1100 °C, to obtain materials of different performance. The chemical, structural and textural characteristics of the composites were determined by FTIR, XRD, TGA-DSC and SEM studies. Their adsorption properties were monitored in terms of Zn (II) binding capacity which could be tailored by changing the template size and sintering temperature. The adsorption capacity of the composite at room temperature was enhanced five times when thermally treated at 900 °C with a maximum adsorption of 3.58 meq/g of the zinc (II). The adsorption could be further optimized to higher values and the materials could be successfully recycled for three consecutive cycles without any significant loss in the adsorption capacity.

The concept of efficiency can be used for comparing the relative performance of various pozzolans when incorporated into concrete. In this paper, an alternative approach for the evaluation of efficiency factor k of a pozzolanic material has been introduced. The method, developed following Abram's strength-W/C ratio rule, calculates efficiency in terms of relative strength and cementitious materials content. The advantage of this method is that only two mixtures are required to determine the k factor of a specific mixture. A laboratory investigation on silica fume (SF) and metakaolin (MK) concrete found that the computed efficiency factors varied with pozzolan type, replacement level and age. At 28 days, the k values ranged from 1.6 to 2.3 for MK and 2.1 to 3.1 for SF mixtures, while at 180 days, the k values varied from 1.8 to 4.0 for MK and 2.4 to 3.3 for SF mixtures. Generally, the k factors increased with age but declined with higher pozzolanic content. It was also observed that change in W/CM ratio from 0.33 to 0.27 did not significantly affect the resultant efficiency factors. © 2004 Elsevier Ltd. All rights reserved.

http://www.sciencedirect.com/science/article/pii/S000888460400242X
http://ac.els-cdn.com/S000888460400242X/1-s2.0-S000888460400242X-main.pdf?_tid=bd7a69b8-7820-11e3-868e-00000aacb360&acdnat=1389156956_b3c258306027f97b5631be2a0618449f

For the first time, sodium cobalt oxide (NaxCo2O4) crystalline thermoelectric materials were obtained using polyvinyl alcohol (PVA) polymerized complex sol-gel solution. PVA was used as polymer solution with sodium acetate/cobalt acetate, followed by calcination at 800oC. The sodium cobalt oxide calcined crystal structures were characterized by X-ray diffraction (XRD). The sol-gel solution calcined at 800oC and then sintered at the same temperature was single crystal and XRD results have an agreement with the literature values. The results indicated that the polymeric sol-gel method is a promising process for the synthesis of sodium cobalt oxide thermoelectric materials.

ТОЛЬКО ОЗНАКОМИТЕЛЬНЫЙ ФРАГМЕНТ, электронная версия не распространяется.

Джон Френч. Алхимические трактаты: о дистилляции, сублимации и кальцинации / Пер. с лат. и ст. англ., коммент. Ю. Ф. Родиченкова, М. Ю. Родыгина; предисл. Б. К. Двинянинова; науч. ред., послесл. М. Ю. Родыгина, под общ. ред. Б. К. Двинянинова. — СПб.: Издательство «Академия исследований культуры», 2022. — 366 с.: ил. — (Серия Librarium Aureum. Opus Majus). ISBN 978-5-94396-242-4

Подарочное издание! Увеличенный формат, тканевая Imperial темно-зеленая твердая обложка с тиснением серебром, плотная бумага блока, более 100 алхимических иллюстраций, уникальные шрифты, приятное оформление, декорированные форзацы, шитый блок, зеленное ляссе и каптал, тираж 300 экз.

Джон Френч (1616–1657) — английский врач и алхимик, магистр искусств закончивший Оксфордский университет и доктор медицины, автор многочисленных трудов, переводчик трех книг «Оккультной философии» Генриха Корнелия Агриппы. В основу настоящего издания вошел главный труд Дж. Френча «Об искусстве дистилляции» изданный в 1651 году, перевод на русский язык публикуется впервые. Этот трактат лабораторно-практического содержания с множеством изображений был довольно популярным многие века, и вполне мог служить учебником для практикующего алхимика или фармацевта. Френч в своей работе опирается на алхимиков прошлого и свою собственную алхимическую практику. Важным дополнением к произведению из VI книг были две главы об иных алхимических операциях: «О сублимации» и «О
кальцинации». В приложение добавлены три предисловия Дж. Френча к английским переводам: «Божественный Пимандр» Гермеса Трисмегиста (в переводе доктора Эверарда), «Новый свет алхимии» М. Сендивогия, «Новые философские печи» И. Р. Глаубера.
В заключение приводится статья переводчика и редактора к. х. н.
Михаила Юрьевича Родыгина, посвященная осмыслению алхимического
труда Джона Френча и памяти, основного переводчика настоящего
издания, к. ф. н. Юрия Фёдоровича Родиченкова.
Книга будет интересна всем тем, кто увлечен философскими идеями прошлых столетий, историей науки, медицины, химии и алхимии, герметизма и герметицизма, историей и теорией западного эзотеризма.

ОГЛАВЛЕНИЕ (без подглав)

Предварительное слово издателя (Двинянинов Б. К.)
Джон Френч. Почтенному другу Джону Дженисону, эсквайру в Даремском епископстве

ДЖОН ФРЕНЧ. ОБ ИСКУССТВЕ ДИСТИЛЛЯЦИИ
Моему высокочтимому другу Тобиасу Гарбранду, доктору медицины и директору Глостер-Холла в Оксфорде
К читателю
КНИГА I. ЧТО ТАКОЕ ДИСТИЛЛЯЦИЯ. ЕЕ ВИДЫ
КНИГА II. О СЛОЖНЫХ ВОДАХ И ДУХАХ
КНИГА III. О МИНЕРАЛАХ
КНИГА IV. O ЖИВОТНЫХ
КНИГА V. РАЗНЫЕ СПАГИРИЧЕСКИЕ ЭКСПЕРИМЕНТЫ
КНИГА VI. СПАГИРИЧЕСКАЯ АНАТОМИЯ ЗОЛОТА И СЕРЕБРА СОДЕРЖАЩАЯ РАЗНЫЕ ДИКОВИНЫ И ОСНОВНЫЕ ИХ РЕЦЕПТЫ

КНИГА VII. О СУБЛИМАЦИИ

КНИГА VIII. О КАЛЬЦИНАЦИИ
Кальцинация металлов

ПРИЛОЖЕНИЯ
Джон Френч. Предисловие к книге Гермеса Трисмегиста «Божественный Пимандр» (в переводе доктора Эверарда), 1650
Предисловие к английскому изданию М. Сендивогия «Новый свет алхимии» в переводе Дж. Френча
Предисловие Дж. Френча к переводу трактата Иоганна Рудольфа Глаубера «Новые философские печи» («Furni novi philosophici») — Амстердам, 1651 г.

ПОСЛЕСЛОВИЕ
Трактат Джона Френча «Об искусстве дистилляции» в координатах алхимической традиции и химической науки. Единство и противоречия реального и воображаемого в ученом творчестве XVII ст. (Родыгин М. Ю.)

БИБЛИОГРАФИЯ

The diatomaceous earth (DE), collected from the Mariovo region in North Macedonia, was characterized and thermally modified. The material represents a sedimentary rock of biogenic origin, soft solid that can be easily disintegrated, with white to grayish color, with bulk density of 0.51–0.55 g/cm3, total porosity of 61–63%, and specific gravity of 2.25 g/cm3. The chemical composition is as follows: SiO2, 86.03; Al2O3, 3.01; Fe2O3, 2.89; MnO, 0.06; TiO2, 0.20; CaO, 0.76; MgO, 0.28; K2O, 0.69; Na2O, 0.19; P2O5, 0.15; and loss of ignition, 5.66 (wt%). The mineralogy of the raw DE is characterized by the predominant presence of amorphous phase, followed by crystalline quartz, muscovite, kaolinite, and feldspar. Significant changes in the opal phase are observed in the 1,000–1,200°C temperature region. At 1,100°C, the entire opal underwent solid–solid transition to cristobalite. Further ramp of the temperature (1,100–1,200°C) induced formation of mullite. Scanning electron microscopy (SE...

In this work the response surface methodology (RSM) in conjunction with the central composite design (CCD) were used to optimize the activity of CaO/Al2O3 solid catalysts for the production of biodiesel. In order to measure the catalyst activity, we used palm oil as a representative raw material for the conversion to biodiesel. The biodiesel production was carried out in a batch laboratory scale reactor. The results showed that both the calcination temperature and the amount of calcium oxide loaded on the support had significant positive effects on the biodiesel yield. The maximum basicity and biodiesel yield obtained were about 194 μmol/g and 94%, respectively. Overall, the catalyst showed high performance at moderate operating conditions and its activity was maintained after two cycles. © 2009 Elsevier B.V. All rights reserved.

http://ac.els-cdn.com/S0926860X09004840/1-s2.0-S0926860X09004840-main.pdf?_tid=37188ce8-2364-11e4-a4f0-00000aacb35d&acdnat=1407987585_84b5785349eaf3dd76ae1aa6727333bb 
http://www.sciencedirect.com/science/article/pii/S0926860X09004840

Electrospinning process was utilized to fabricate lanthanum doped bismuth ultrafine nanofibers. PVA was used as precursor polymer solution with bismuth acetate/lanthanum acetate, followed by calcination at 800oC. The produced nanofibers and calcined crystal structures were characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The results indicated that samples after calcination should be sintered more than one to obtain pure crystalline phase.

Zinc oxide (ZnO) based fibers with a diameter of 80-100 nm were prepared by electrospinning. Polyvinyl alcohol (PVA) and zinc acetate dihydrate were dissolved in water and the polymer/salt solution was electrospun at 2.5 kV cm(-1). The resulting electrospun fibers were subjected to calcination at 500°C for 2h to obtain ZnO-based fibers. Humidity sensing properties of the fiber mats were investigated by quartz crystal microbalance (QCM) method and electrical measurements. The adsorption kinetics under constant relative humidity (RH) between 10% and 90% were explained using Langmuir adsorption model. Results of the measurements showed that ZnO-based fibers were found to be promising candidate for humidity sensing applications at room temperature.

Yemeni clays (bentonite and kaolin) were used as catalysts and catalysts supported metals ions Ce, Pt, Pt-Ce, Pd, Pd-Ce, for the debutylation reaction of 2tert-butylphenol. The two clays were characterized using atomic absorption spectroscopy, particle size analyzer and N2-BET adsorption method. The activity of debutylation reaction was found to depend on the type of the catalyst. Kaolin based catalysts were more active than those bentonite based. The Selectivity of the catalysts was found to depend on the type of treatment that each catalyst was subjected to. The catalysts that were treated by calcination were more selective towards phenol formation (debutylation reaction of 2-tertbutylphenol), while those treated by reduction were more selective toward the formation of 4-tertbutylphenol (isomerization reaction of 2-tertbutylphenol).

Nickel zinc ferrite sampless were synthesized from metal nitrates precursors via solution auto combustion method, using different synthesis conditions.. Samples were prepared at different temperatures 400 o C, 600 o C, 800 o C and 1000 o C with heating rate 10 o /min. for 4 hours. The optical measurements are carried out by a FTIR. The nickel zinc ferrite exhibits a single-spinel structure. From FTIR spectrum two fundamental bands around 600–400cm-1 were observed, that are the common features of all ferrite materials. Improved optical properties was found for sample prepared at 1000 o C for 4 hours (with 10 o /min) show better Sample prepared at 10 o /min.(800 o C for 4hours) show improved results as compared to sample at 25 o C/min(800 o C for 4 hours).

The concept of efficiency can be used for comparing the relative performance of various pozzolans when incorporated into concrete. In this paper, an alternative approach for the evaluation of efficiency factor k of a pozzolanic material has been introduced. The method, developed following Abram's strength–W/C ratio rule, calculates efficiency in terms of relative strength and cementitious materials content. The advantage of this method is that only two mixtures are required to determine the k factor of a specific mixture. A laboratory investigation on silica fume (SF) and metakaolin (MK) concrete found that the computed efficiency factors varied with pozzolan type, replacement level and age. At 28 days, the k values ranged from 1.6 to 2.3 for MK and 2.1 to 3.1 for SF mixtures, while at 180 days, the k values varied from 1.8 to 4.0 for MK and 2.4 to 3.3 for SF mixtures. Generally, the k factors increased with age but declined with higher pozzolanic content. It was also observed that change in W/CM ratio from 0.33 to 0.27 did not significantly affect the resultant efficiency factors.

The production of hydroxyapatite (HA) from bovine bones was studied in this paper. Bovine hydroxyapatite (BHA) was produced from bovine bone powders by calcination without compaction. The powders were calcined at temperatures ranging from 700-1100 degrees C. It was discovered that sample preparation has some influence on the calcination behavior of the bovine bone powders. XRD results confirmed that HA has been successfully produced but traces of alpha-TCP and beta-TCP were also found. The Ca/P ratios of the BHA powders produced from the process have values greater than 2.0.

http://link.springer.com/chapter/10.1007/978-3-540-68017-8_39

"The sinterability of calcined synthesized HA (700°C to 1000°C) was investigated over the temperature range of 1050°C to 1350°C in terms of phase stability, bulk density, Young's modulus and Vickers hardness. Calcination has resulted in higher crystallinity of the starting synthesized HA powder. Decomposition of HA phase to form secondary phases was not observed in the present work for the calcined powders. The results also indicated that calcination of the HA powder prior to sintering has negligible effect on the sinterability of the HA compacts (up to 900°C). Further treatment at 1000°C was found to be detrimental to the properties of sintered HA.


http://link.springer.com/chapter/10.1007/978-3-642-21729-6_18

Exploring faster, safer, and more efficient energy storage devices will motivate scientists to develop novel energy storage products with high performance. Herein, we report porous NiO nanoparticles have been prepared by a simple hydrothermal method with CTAB and laboratory tissue paper as a template followed by calcination at three different temperatures (300, 500, and 700 °C). The electrochemical characteristics of the prepared materials were examined in a three-electrode cell configuration using aqueous potassium hydroxide (2.0 M KOH) electrolyte. The NiO-300 electrode displayed the supreme capacitance of 568.7 F g−1 at 0.5 A g−1. The fascinating NiO morphology demonstrates a crucial part in offering simple ion transport, shortening electron, and ion passage channels and rich energetic spots for electrochemical reactions. Finally, the asymmetric supercapacitor (ASC), NiO//AC was constructed using positive and negative electrode materials of NiO-300 and activated carbon (AC), resp...

Full-text available at:  http://rdcu.be/v7Fn 
Abstract:
A one-pot polymerization method using citric acid and glucose for the synthesis of nano-crystalline BaFe0.5Nb0.5O3 is described. Phase evolution and the development of the crystallite size during decomposition of the (Ba,Fe,Nb)-gel were examined up to 1100 °C. Calcination at 850 °C of the gel leads to a phase-pure nano-crystalline BaFe0.5Nb0.5O3 powder with a crystallite size of 28 nm. The shrinkage of compacted powders starts at 900 °C. Dense ceramic bodies (relative density > 90 %) can be obtained either after conventional sintering above 1250 °C for 1 h or after two-step sintering at 1200 °C. Depending on the sintering regime the ceramics have average grain sizes between 0.3 µm and 52 µm. The optical band gap of the nano-sized powder is 2.75(4) eV and decreases to 2.59(2) eV after sintering. Magnetic measurements of ceramics reveal a Néel temperature of about 23 K. A weak spontaneous magnetization might be due to the presence of a secondary phase not detectable by XRD. Dielectric measurements show that the permittivity values increase with decreasing frequency and rising temperature. The highest permittivity values of 10.6x10^4 (RT, 1 kHz) were reached after sintering at 1350 °C for 1 h. Tan d values of all samples show a maximum at 1-2 MHz at RT. The frequency dependence of the impedance can be well described using a single RC-circuit.

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