Recent research activities on the linear magnetoelectric (ME) effect?induction of magnetization by an electric field or of polarization by a magnetic field?are reviewed. Beginning with a brief summary of the history of the ME effect since its prediction in 1894, the paper focuses on the present revival of the effect. Two major sources for 'large' ME effects are identified. (i) In composite materials the ME effect is generated as a product property of a magnetostrictive and a piezoelectric compound. A linear ME polarization is induced by a weak ac magnetic field oscillating in the presence of a strong dc bias field. The ME effect is large if the ME coefficient coupling the magnetic and electric fields is large. Experiments on sintered granular composites and on laminated layers of the constituents as well as theories on the interaction between the constituents are described. In the vicinity of electromechanical resonances a ME voltage coefficient of up to 90?V?cm?1?Oe?1 is achieved, which exceeds the ME response of single-phase compounds by 3?5 orders of magnitude. Microwave devices, sensors, transducers and heterogeneous read/write devices are among the suggested technical implementations of the composite ME effect. (ii) In multiferroics the internal magnetic and/or electric fields are enhanced by the presence of multiple long-range ordering. The ME effect is strong enough to trigger magnetic or electrical phase transitions. ME effects in multiferroics are thus 'large' if the corresponding contribution to the free energy is large. Clamped ME switching of electrical and magnetic domains, ferroelectric reorientation induced by applied magnetic fields and induction of ferromagnetic ordering in applied electric fields were observed. Mechanisms favouring multiferroicity are summarized, and multiferroics in reduced dimensions are discussed. In addition to composites and multiferroics, novel and exotic manifestations of ME behaviour are investigated. This includes (i) optical second harmonic generation as a tool to study magnetic, electrical and ME properties in one setup and with access to domain structures; (ii) ME effects in colossal magnetoresistive manganites, superconductors and phosphates of the LiMPO4 type; (iii) the concept of the toroidal moment as manifestation of a ME dipole moment; (iv) pronounced ME effects in photonic crystals with a possibility of electromagnetic unidirectionality. The review concludes with a summary and an outlook to the future development of magnetoelectrics research.

https://iopscience.iop.org/article/10.1088/0022-3727/38/8/R01/pdf

Revival of the Magnetoelectric Effect

Mechanical properties of nanocrystalline materials

The development of novel materials is a fundamental focal point of chemical research; and this interest is mandated by advancements in all areas of industry and technology. A good example of the synergism between scientific discovery and technological development is the electronics industry, where discoveries of new semiconducting materials resulted in the evolution from vacuum tubes to diodes and transistors, and eventually to miniature chips. The progression of this technology led to the development * To whom correspondence should be addressed. B.L.C.: (504) 2801385 (phone); (504) 280-3185 (fax); bcushing@uno.edu (e-mail). C.J.O.: (504)280-6846(phone);(504)280-3185(fax);coconnor@uno.edu (e-mail). 3893 Chem. Rev. 2004, 104, 3893−3946

http://depa.fquim.unam.mx/amyd//archivero/FidelmarLechugaSanabria_4940.pdf

Recent advances in the liquid-phase syntheses of inorganic nanoparticles.

Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40th anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are dee...

Fundamentals and Catalytic Applications of CeO2-Based Materials

Use of CeO2-based oxides in the three-way catalysis

Zinc oxide nano-particles with different morphologies have been obtained by controlling different parameters of the precipitation process: solution concentration, pH and washing medium. The reactions leading to the formation of zinc metastable complexes were followed by potentiometric and conductimetric titrations. During the ethanol washing step the intermediate zinc complexes have been modified by weathering and solution processes which drived both the phase transformation reactions and the particles recrystallization. The nucleation of zinc alkoxides during this process is an “organic matrix-mediated” process, where the matrix is formed on the intermediate zinc complexes surface during the NH 4 OH addition to the solution of the zinc precursor. The existence of this matrix has been supported by FTIR. The transformation of the zinc metastable complexes during the washing with ethanol was followed with XRD. Through this process it is possible to obtain agglomerates of zinc oxide nanoparticles from a random network, as was revealed by SEM and TEM.

Controlled precipitation methods: formation mechanism of ZnO nanoparticles

A Strategic Two‐Stage Low‐Temperature Thermal Processing Leading to Fully Dense and Fine‐Grained Doped‐ZnO Varistors

https://hal-univ-rennes1.archives-ouvertes.fr/hal-01216294/document

Recent advances in perovskites: Processing and properties

The phase relationships over a wide range of temperature and compositions in the ZrO2-CeO2 system have been reinvestigated. From DTA results, thermal expansion measurements andKIC determinations it was established that additions of CeO2 to ZrO2 decreases the monoclinic to tetragonal ZrO2 transition temperature, from 990 ° C to 150 ∓ 50 ° C, and an invariant eutectoid point at approximately 15 mol% CeO2 exists. The extent of the different single- and two-phase fields were determined with precise lattice parameter measurements on quenched samples. Evidence for the existence of a binary compound Ce2Zr3O10 (o-phase) was obtained by X-ray diffraction. The o-phase was stable below approximately 800 ° C, above which it decomposes into tetragonal zirconia + fluorite ceria solid solutions. Taking into account the polymorphic tetragonal-cubic transition and the narrowness of the two-phase tetragonal zirconia + fluorite ceria field above 2000 ° C, the existence of a new invariant eutectoid point was assumed, in which the metastable fluorite zirconia solid solution decomposes into tetragonal zirconia + fluorite ceria solid solutions. From the results obtained, the phase diagram also incorporates a eutectic point located at approximately 2300 ° C and 24 mol % CeO2.

A new tentative phase equilibrium diagram for the ZrO2-CeO2 system in air

High-temperature piezoelectric ceramics based on W6+-doped Bi4Ti3O12 (W-BIT) were prepared by both the conventional mixing oxides and the chemical coprecipitation methods. Sintering was carried out between 800° and 1150°C in air. A rapid densification, >99% of the theoretical density (rhoth) at 900°C/2 h, took place in the chemically prepared W6+-doped Bi4Ti3O12 ceramics, whereas conventionally prepared BIT-based materials achieved a lower maximum density, ∼94% of rhoth, at higher temperature (1050°C). The microstructure study revealed a platelike morphology in both materials. Platelike grains were larger in the conventionally prepared W-BIT-based materials. The sintering behavior could be related both to the agglomeration state of the calcined powders and to the enlargement of the platelets at high temperature. The W6+-doped BIT materials showed an electrical conductivity value 2-3 orders of magnitude lower than undoped samples. The electrical conductivity increased exponentially with the aspect ratio of the platelike grains. The addition of excess TiO2 produced a further decrease of the electrical conductivity.

Carlos Moure

Papers

Controlled precipitation methods: formation mechanism of ZnO nanoparticles

A Strategic Two‐Stage Low‐Temperature Thermal Processing Leading to Fully Dense and Fine‐Grained Doped‐ZnO Varistors

Recent advances in perovskites: Processing and properties

A new tentative phase equilibrium diagram for the ZrO2-CeO2 system in air

Factors Affecting the Electrical Conductivity of Donor‐Doped Bi4Ti3O12 Piezoelectric Ceramics