FERROELECTRIC NANOCOMPOSITES WITH GOVERNED INTERFACE ON BASE OF MAGNETIC POROUS GLASSES

Two-phase (nonporous) magnetic alkali borosilicate glasses have been produced by induction melting. Their macroscopic properties and crystal structure have been studied and it is shown that in the silica skeleton there are the agglomerates of Fe3O4. These agglomerates are formed by monodomain nanoparticles of magnetite and demonstrate the superparamagnetic properties. After special thermal treatment (liquation process) and chemical etching the nanoporous matrices with random dendrite pore structure and magnetic properties have been produced. The channels (porous space) were filled by ferroelectric materials KH2PO4 (KDP), KH2PO4+(NH4)H2PO4 (KDP-ADP or KADP), and NaNO2 and the effect of applied magnetic fields on phase transitions in these nanocomposite have been studied. It has also been established that a restricted geometry changed essentially the phase diagram of KADP.

Temperature evolution of the magnetic properties of lanthanum-strontium manganites

The temperature dependences of the magnetization M(T) for multiferroic single crystal lanthanum-strontium manganites La0.875Sr0.125MnO3 (LSMO-0.125) and La0.93Sr0.07MnO3 (LSMO-0.07) have been obtained. It is shown that the phase transitions (PT) in LSMO-0.07 at TC=125.8(1,5) K and in LSMO-0.125 at TC1=181.2 (1.5) belong to the second order type. The phase transition in LSMO-0.125 at TC2=157.6 (1.5) K is the first order PT. From the M–1(T) curves, the values of the magnetic moments have been determined. They are equal to μ1=2.47(1) μB/Mn and μ2=2.82(1) μB/Mn, for LSMO-0.125 and LSMO-0.07 respectively

An analysis of the high-temperature phase structure of multiferroic solid solutions of the PFW–PT

The temperature evolution of multiferroic solid solutions of the PFW–PT system, namely a (1–x)Pb(Fe2/3W1/3O3)–(x)PbTiO3 crystal structure where x = 0, 0.2, 0.3, has been studied by neutron powder diffraction in the region of the morphotropic phase boundary. The coexistence of cubic and tetragonal phases in the solutions with x = 0.2, 0.3 was found below T = 259 and 285K, respectively. As a result of the data treatment, the atom coordinates, the occupation factors and the temperature dependences of cell parameters were determined in the cubic perovskite phase. The refinement of the crystal structure in terms of ideal perovskite exhibited anomalously large Debye–Waller factors for the lead cations, indicating the appearance of random static displacements of these cations from the ideal perovskite (000) position. Using the split-ion model we estimated the value of Pb static shifts (∼0.1Å) from their high-symmetry positions along the [110] direction. It was shown that these shifts decrease with increasing the PbTiO3 concentration

Tuning the mechanical and thermal properties of (MgNiCoCuZn)O by intelligent control of cooling rates

The possibility of altering the phase equilibria of multicomponent oxide systems through precise control of configurational entropy has opened a platform with unlimited possibilities to fine-tune material properties. The current work is aimed at tailoring the mechanical and thermal properties of (MgNiCoCuZn)O by an intelligent design of constituent phase structure resulting from controlled cooling from the stabilization temperature. Based on the cooling rates, the amount of CuO nucleation was found to vary between 5.4 and 12.3 wt%, along with a corresponding decrease in Cu2+ content in the matrix. It was observed that with the decrease in Cu2+ ion concentration in the matrix, the Young's modulus and hardness increased by 33% and 26%, respectively, along with a corresponding decrease in the coefficient of thermal expansion by 15%. Similarly, an increased nucleation of CuO precipitates led to the improvement of fracture toughness of the material by 15%, while its thermal conductivity remained unaltered