Crystallographic and magnetic identification of secondary phase in orientated Bi<inf>5</inf>Fe<inf>0.5</inf>Co<inf>0.5</inf>Ti<inf>3</inf>O<inf>15</inf> ceramics

Abstract

Type of publicationArticle (peer-reviewed) The fabrication of highly-oriented polycrystalline ceramics of Bi 5 Fe 0.5 Co 0.5 Ti 3 O 15 , prepared via molten salt synthesis and uniaxial pressing of high aspect ratio platelets is reported. Electron backscatter images show a secondary phase within the ceramic which is rich in cobalt and iron. The concentration of the secondary phase obtained from scanning electron microscopy is estimated at less than 2% by volume, below the detection limit of x-ray diffraction (XRD). The samples were characterized by x-ray diffraction, polarization-electric field measurements, superconducting quantum interference device as a function of sample orientation and vibrating sample magnetometry as a function of temperature. It is inferred from the data that the observed ferromagnetic response is dominated by the secondary phase. This work highlights the importance of rigorous materials characterisation in the study of multiferroics as small amounts of secondary phase, below the limit of XRD, can lead to false conclusions. V C 2012 American Institute of Physics.[http://dx

Room temperature electromechanical and magnetic investigations of ferroelectric Aurivillius phase Bi5Ti3(FexMn1−x)O15 (x = 1 and 0.7) chemical solution deposited thin films

“…The occurrence of weak ferromagnetic behaviour in these compounds was attributed to local ferromagnetic Fe-O-Fe interactions; therefore, random distribution of the ironoxygen and titanium-oxygen octahedra in the different BTFO compounds investigated may account for the variation in the observed magnetic behaviour. On the other hand, our previous investigations of the Bi 37 demonstrated that the observed ferromagnetic response was accounted for by the presence of trace amounts of second-phase ferromagnetic inclusions (undetected by x-ray diffraction measurements), whereas no magnetic response from the main Aurivillius phase was detectable. The previous reports 19,20,36 of ferromagnetic response in BTFO do not discuss the possibility of spinel phases such as iron oxide contributing to the ferromagnetic response observed.…”

The structural and piezoresponse properties of c-axis-oriented Aurivillius phase Bi5Ti3FeO15 thin films deposited by atomic vapor deposition

“…8 Previous work undertaken on BTFO has shown it to be both ferroelectric, with a Curie temperature of about 730 C, 9 and to possess antiferromagnetic order, with a Neel point of 80 K. 10 The magneto-electric coupling behavior 11 and an obvious magnetocapacitance effect 12 have also been observed. By Nd-doping 13 or by substituting Fe with the Co 14 BTFO, solid-solution films have been reported to exhibit ferromagnetism to some degree, although recent work 15,16 has shown that great care must be taken, when interpreting ferromagnetic responses, to eliminate the effects of ferromagnetic second phases, even at very low levels. In addition, Jang et al 17 reported the photocatalytic and the photoelectrochemical performance of BTFO material for photo-current generation under visible light (k !…”

“…[11][12][13][14][15][16][17][18][19] While methods such as sol-gel, 12,19 solid-state reaction, 17,18 and pulsed laser deposition 4 20,21 Atomic vapor deposition (AVD) is based on pulsed liquid-injection chemical vapor deposition with a volume of each pulse of the order of microlitres. 22 It has been proved that AVD can deposit high-quality high-k dielectric or ferroelectric films with a largely uniform film thickness, composition, and electrical properties and is highly suitable for mass production.…”

Measuring room-temperature intrinsic multiferroic properties by excluding the secondary magnetic inclusion contribution

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main phase or from the secondary phase formed during the sample preparation is still under debate [12,13]. Therefore, some new methods or sensible techniques have to be developed to identify intrinsic multiferroic responses in studying suc h complicated layered oxides.

Normally, the X-ray diffraction (XRD) method provides a direct way to detect a secondary phase i n powders, thin films or bulk ceramics, but this method cannot deal with the case that the weight ratio of the impurity is below a certain critical level (~5 wt.%, for example).

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“…main phase or from the secondary phase formed during the sample preparation is still under debate [12,13]. Therefore, some new methods or sensible techniques have to be developed to identify intrinsic multiferroic responses in studying suc h complicated layered oxides.…”