PTCR anomaly in barium-titanate-based composites

Zajc, I.; Drofenik, Miha

doi:10.1016/j.ceramint.2014.01.001

Cited by 10 publications

(2 citation statements)

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“…This isolating phase is crucial and must exhibit, at a distinct temperature, an irregularity, i.e., a significant change in the temperature coefficient of expansion [5], a crystal transformation, and/or change in its crystal morphology [6]. Recently, a new type of PTCR composite based on the phenomenon known as the ''ferroelectric phase-transition-assisted anomaly in the electrical resistivity'' (FPTAA) was reported [7,8]. Here, the BaTiO 3 @Ni composite was considered in the context of the recently reported FPTAA phenomenon.…”

Section: Introductionmentioning

confidence: 99%

The jump-like PTCR effect in a Ni-BaTiO3 magnetic composite

Zajc

Drofenik

2022

J Mater Sci: Mater Electron

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The ceramic composites BaTiO3@Ni, composed of a conducting nickel and a highly resistive ferroelectric BaTiO3 phase, exhibiting a positive temperature coefficient of electrical resistivity (PTCR), are prepared using a conventional ceramic method at less than 1000 °C. The BaTiO3@Ni composites show a jump-like PTCR effect in electrical resistivity by about eight orders of magnitude (ρmax/ρmin ≈ 108) with ρmin < 1 Ωcm. This is the first example of a standard PTCR element with a relatively high magnetization. The grain relocations (a microstructural rearrangement) on a microscopic scale in the composite are filmed using a transmission electron microscope while heating through the ferroelectric phase transition (Curie temperature), which induces the PTCR anomaly. The resistivity anomaly of the composite is explained in terms of the ferroelectric phase transition-assisted anomaly in the electrical resistivity.

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Section: Introductionmentioning

confidence: 99%

The jump-like PTCR effect in a Ni-BaTiO3 magnetic composite

Zajc

Drofenik

2022

J Mater Sci: Mater Electron

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“…At the Curie temperature, BaTiO 3 undergoes a ferroelectric-to-paraelectric transition. Polycrystalline n-type semiconducting barium titanate (BaTiO 3 ) exhibits a behavior known as the positive temperature coefficient of resistivity (PTCR) effect, although it has been also reported that single crystals exhibit a negative coefficient (NTCR), as shown infigure 16.a[92][93][94][95][96][97]. The resistance increase is predominantly associated with an increase in the grain-boundary barrier height, therefore it is important to gain information about the grain boundary character in these devices.Figures 16.b and 16.c present some additional features of such devices, respectively the multilayer structure and a flow sheet of its processing.Donor dopant incorporation is achieved by either electronic compensation at low concentration of dopants, or by vacancy compensation at high concentration.…”

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Recent advances in perovskites: Processing and properties

Moure

Peña

2015

Progress in Solid State Chemistry

170

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The perovskite structure is one of the most wonderful to exist in nature. It obeys to a quite simple chemical formula, ABX 3 , in which A and B are metallic cations and X, an anion, usually oxygen. The anion packing is rather compact and leaves interstices for large A and small B cations. The A cation can be mono, di or trivalent, whereas B can be a di, tri, tetra, penta or hexavalent cation. This gives an extraordinary possibility of different combinations and partial or total substitutions, resulting in an incredible large number of compounds. Their physical and chemical properties strongly depend on the nature and oxidation states of cations, on the anionic and cationic stoichiometry, on the crystalline structure and elaboration techniques, etc.In this work, we review the different and most usual crystalline representations of perovskites, from high (cubic) to low (triclinic) symmetries, some well-known preparation methods, insisting for instance, in quite novel and original techniques such as the mechanosynthesis processing. Physical properties are reviewed, emphasizing the electrical (proton, ionic or mixed conductors) and catalytic properties of Mn-and Co-based perovskites ; a thorough view on the ferroelectric properties is presented, including piezoelectricity, thermistors or pyroelectric characteristics, just to mention some of them ; relaxors, microwave and optical features are also discussed, to end up with magnetism, superconductivity and multiferroïsme.Some materials discussed herein have already accomplished their way but others have promising horizons in both fundamental and applied research.To our knowledge, no much work exists to relate the crystalline nature of the different perovskite-type compounds with their properties and synthesis procedures, in particular with the most recent and newest processes such as the mechanosynthesis approach. Although this is not intended to be a full review of all existing perovskite materials, this report offers a good compilation of the main compounds, their structure and microstructure, processing and relationships between these features.

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