CaCu3Ti4-xRuxO12: Crystal structure, electrical and magnetic properties

The CaCu3 Ti 4 O12 belongs to the large ACu3B4 O12 family of materials. Crystallographic A site is most often occupied by alkaline-earth metals or lanthanides, while B site is occupied by transition metals. The type of cations that build up the structure strongly affects the properties of these. The CaCu 3 Ti 4 O12 has been extensively studied due to its high dielectric permittivity stable over a wide temperature and frequency range (up to 10 5 , for 100-600 K and 10 2 –105 Hz). Because of such characteristics, it has promising application in microelectronics. However, it has been shown that differences in the crystal structure and electrical properties of dielectric ceramics and metallic electrodes, may cause an energy barrier and occurrence of stress on the ceramic-electrode contact which reduces dielectric permittivity. Such stress can be prevented by using dielectric and electrode materials with as much as possible similar crystal structure, especially unit cell parameters. This investigation dealt with detailed structural (XRPD, HRTEM, SAED), dielectric and magnetic study of CaCu 3 Ti 4-xRuxO12 (CCTRO, x = 0, 1 and 4) materials. The results of structural refinement show that in cubic symmetry with space group 3Im , both titanium and ruthenium ions occupied crystallographic B site. Moreover, the variation in stoichiometry slightly affects the value of the unit cell parameters but changes electrical properties of studied material. Thus, substitution of even one atom of Ru in CaCu3 Ti 4-xRuxO12 unit cell is enough to change material properties from dielectric to conductor solving the problem of stress appearance on the contact layer of dielectric/electrode in capacitors.IX Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 20-21, 2021; Belgrad

Adsorption behavior of Eu(III) on partially Fe(III)- or Ti(IV)-coated silica

The adsorption behavior of Eu(III) onto silica surface, which was partially coated with Fe(III) or Ti(IV), was investigated to determine Fe(III) or Ti(IV) effects on the surface reaction of lanthanides on mineral surfaces in groundwater. Compared with a parallel uncoated silica, the Fe(III)-coated silica did not enhance the adsorption of Eu(III). However, enhanced adsorption of Eu(III) on the Ti(IV)-coated silica was observed by increasing the amount of Ti(IV) on the silica surface

Crystal Structure and Electrical Properties of Ruthenium-Substituted Calcium Copper Titanate

This paper reports a detailed study of crystal structure and dielectric properties of ruthenium-substituted calcium-copper titanates (CaCu3Ti4−xRuxO12, CCTRO). A series of three samples with different stoichiometry was prepared: CaCu3Ti4−xRuxO12, x = 0, 1 and 4, abbreviated as CCTO, CCT3RO and CCRO, respectively. A detailed structural analysis of CCTRO samples was done by the Rietveld refinement of XRPD data. The results show that, regardless of whether Ti4+ or Ru4+ ions are placed in B crystallographic position in AA’3B4O12 (CaCu3Ti4−xRuxO12) unit cell, the crystal structure remains cubic with Im3¯ symmetry. Slight increases in the unit cell parameters, cell volume and interatomic distances indicate that Ru4+ ions with larger ionic radii (0.62 Å) than Ti4+ (0.605 Å) are incorporated in the CaCu3Ti4−xRuxO12 crystal lattice. The structural investigations were confirmed using TEM, HRTEM and ADF/STEM analyses, including EDXS elemental mapping. The effect of Ru atoms share in CaCu3Ti4−xRuxO12 samples on their electrical properties was determined by impedance and dielectric measurements. Results of dielectric measurements indicate that one atom of ruthenium per CaCu3Ti4−xRuxO12 unit cell transforms dielectric CCTO into conductive CCT3RO while preserving cubic crystal structure. Our findings about CCTO and CCT3RO ceramics promote them as ideal tandem to overcome the problem of stress on dielectric-electrode interfaces in capacitors

Study of the floristic composition of fir-spruce-beech forests in Serbia and Bosnia-Herzegovina

The mixed forest of fir, spruce, and beech (Piceo-Abietetum Čolić 1965) is an important and widespread plant community on the Balkan Peninsula. Within the Dinarides, it occupies the upper zone of the beech-fir forest belt, establishing a regional belt of vegetation in the Illyrian province. This community occupies significant areas in western and southwestern Serbia where it also creates a regional belt, thus confirming that this part of Serbia belongs to the Illyrian floral-geographical province. This paper compares the floristic composition of the fir-spruce-beech forests in Serbia and Bosnia-Herzegovina in order to determine the differences between the study stands. A total of 29 relevés were analyzed, 17 from the mountain of Lisina (Bosnia-Herzegovina) and 12 from the Pešter plateau (Serbia). Cluster analysis revealed a clear differentiation between the study stands and species in Bosnia-Herzegovina and those in Serbia. The main difference is in the dominant species: Fagus moesiaca (K. Maly) Czecz. in Serbia and Fagus sylvatica L. in Bosnia-Herzegovina. In Bosnia-Herzegovina, the forest grows under conditions of a uniform, maritime and humid climate, while in Serbia it grows under conditions of a continental climate with less rainfall and a strong zoo-anthropogenic impact. Regarding the spectrum of life forms, there are more phanerophytes and geophytes in Bosnia-Herzegovina than in Serbia. On the other hand, the spectrum of floral elements in Serbia is richer in xerophilous, Balkan and sub-Mediterranean floral elements