@prefix prodottidellaricerca: . @prefix istituto: . @prefix prodotto: . istituto:CDS073 prodottidellaricerca:prodotto prodotto:ID297090 . @prefix pubblicazioni: . @prefix unitaDiPersonaleInterno: . unitaDiPersonaleInterno:MATRICOLA7421 pubblicazioni:autoreCNRDi prodotto:ID297090 . unitaDiPersonaleInterno:MATRICOLA29201 pubblicazioni:autoreCNRDi prodotto:ID297090 . @prefix unitaDiPersonaleEsterno: . unitaDiPersonaleEsterno:ID22597 pubblicazioni:autoreCNRDi prodotto:ID297090 . unitaDiPersonaleEsterno:ID22598 pubblicazioni:autoreCNRDi prodotto:ID297090 . @prefix modulo: . modulo:ID8166 prodottidellaricerca:prodotto prodotto:ID297090 . @prefix rdf: . prodotto:ID297090 rdf:type prodotto:TIPO1304 . @prefix retescientifica: . prodotto:ID297090 rdf:type retescientifica:ProdottoDellaRicerca . @prefix rdfs: . prodotto:ID297090 rdfs:label "Preparation and dielectric investigations of Ba0.60Sr0.40TiO3 ferroelectric ceramics with different degree of porosity (Abstract/Poster in convegno)"@en . @prefix xsd: . prodotto:ID297090 pubblicazioni:anno "2014-01-01T00:00:00+01:00"^^xsd:gYear . @prefix skos: . prodotto:ID297090 skos:altLabel "
R. Stanculescu 1, I. Ciuchi 1,2, I. Turcan 1, P. Galizia 2, C. Capiani 2, C. Galassi 2 and L. Mitoseriu 1 (2014)
Preparation and dielectric investigations of Ba0.60Sr0.40TiO3 ferroelectric ceramics with different degree of porosity
in ELECTROCERAMICS XIV, Bucarest (Romania), 16-20 giugno 2014
"^^rdf:HTML ; pubblicazioni:autori "R. Stanculescu 1, I. Ciuchi 1,2, I. Turcan 1, P. Galizia 2, C. Capiani 2, C. Galassi 2 and L. Mitoseriu 1"^^xsd:string ; pubblicazioni:altreInformazioni "http://www.electroceramics14.com/images/PDF/Abstract%20Book%20Electroceramics%20XIV.pdf\n\nhttp://www.electroceramics14.com/images/PDF/Final%20Program%20EC%20XIV.pdf"^^xsd:string ; skos:note "Abstract"^^xsd:string ; pubblicazioni:affiliazioni "1 Faculty of Physics, Alexandru Ioan Cuza University, Iasi, 700506, Romania\n2 ISTEC-CNR, Via Granarolo, no.64, I - 48018, Faenza, Italy"^^xsd:string ; pubblicazioni:titolo "Preparation and dielectric investigations of Ba0.60Sr0.40TiO3 ferroelectric ceramics with different degree of porosity"^^xsd:string ; prodottidellaricerca:abstract "By introducing a controlled porosity into the ceramic systems, the properties can be improved and\nmake the material proper for being used as high-frequency ultrasonic transducers or for tunable applications.\nThe tailored porosity exposes special properties and characteristics of the materials, which might be\ncompletely different than their conventional dense equivalents.\nThe aim of this study was to characterize (Ba,Sr)TiO3 ceramics with different porosity levels. Powders\nwith the composition Ba0.60Sr0.40TiO3 (BST) were prepared following the mixed oxide method by solid-state\nreaction at a sintering temperature of 1450\u00B0C for 2h. The BST ceramics with various porosities have been\nprepared by addition of lamellar graphite in concentration of 10, 20 and 35%.\nThe effect of addition of graphite on dielectric properties was investigated. We noticed that the\nincreasing of the amount of graphite increases the graded porosity and leads to a low mechanical quality\nfactor. The relative density of the obtained samples varies from values around 95% for the dense ceramic to\n66% for porous ceramics. Graphite was burned out through the sintering process and this resulted in a\nmodification of morphology, microstructure and pore density of the ceramic product. The porous samples\nproduced with homogeneous or graded porosity show a strong difference of the dielectric properties and\nmicrostructure in comparison with the dense ceramic samples. The role of anisotropic porosity on the\nfunctional properties on the dielectric properties is discussed. Microstructural, morphological and dielectric\ninvestigations have been performed and data were compared with other literature studies.\nFrom SEM analysis it was found that with addition of graphite as pore forming the samples present a\nfracture mode transformation from intragranular fracture to an intergranular fracture and a decreasing of grain\nsize of BST. Furthermore, as BST grain size becomes smaller, the volume of grain boundary increases and\nthe crack prefers spreading along grain boundary to splitting the strengthened grain.\nThe Impedance Spectroscopy analyse was performed in the temperature range of (21-200)\u00B0C and frequency\nof 20Hz-2MHz. The dielectric investigations have shown that the dielectric constant of the Ba0.60Sr0.40TiO3\n(BST) ceramics with different degree of porosity, decrease and remains constant at higher frequency,\nindicating dielectric dispersion. The frequency dependence of the real and imaginary part of permittivity\npresent a few characteristic relaxations which appear in the specific frequency ranges: (i) the increasing of the\nreal and imaginary parts of permittivity at low frequencies below 100Hz for the compositions with x=10, 20 and\n35% graphite is most probably associated to the thermally activated space charge effects (Maxwell-Wagner\nphenomena) and (ii) anomalies of the imaginary part of permittivity above 103Hz, for samples with x=10 and\n20% porosity, which seems to be related to a Debye-type relaxation process. The dielectric properties of the\ninvestigated ceramics were characterized and correlated with their microstructure. From dielectric constant\ndependence with temperature, a shift of Curie temperature of ceramics was observed and possible reasons for\nthese effects were interpreted.\nAcknowledgements: This work was financially supported by CNCS-UEFISCDI projects PNII-ID-PCE-2011-3-\n0745 and by ERASMUS placement programme between Univ. \\\"Al. I. Cuza\\\" Iasi & ISTEC-CNR Faenza, Italy.\nThe collaboration in frame of the COST Action MP0904 is highly acknowledged."@en ; prodottidellaricerca:prodottoDi modulo:ID8166 , istituto:CDS073 ; pubblicazioni:autoreCNR unitaDiPersonaleInterno:MATRICOLA29201 , unitaDiPersonaleInterno:MATRICOLA7421 , unitaDiPersonaleEsterno:ID22597 , unitaDiPersonaleEsterno:ID22598 .