A-site ordered state in manganites with perovskite-like structure based on optimally doped compounds Ln0.70Ba0.30MnO3（Ln=Pr,Nd）

In this paper,we report on the crystal structure and magnetic properties of the nano structured Baordered phases of rare-earth manganites obtained from the optimally doped solid solutions Ln0.70Ba0.30MnO3(Ln=Pr,Nd).The materials were studied by X-ray diffraction,scanning electron microscopy,energy dispersive spectroscopy and SQUID-magnetometry techniques.It is found that states with different degrees of cation ordering in the A-sublattice of the ABO3 perovskite can be obtained by employing special conditions of chemical treatment.In particular,reduction of the parent compounds results in the formation of a nanocomposite containing ferrimagnetic anion-deficient ordered phase LnBaMn2O5.Oxidation of the composite does not change an average size of the nanocrystallites,but drastically alters their phase composition to stabilize ferromagnetic stoichiometric ordered phase LnBaMn2O6 and ferromagnetic superstoichiometric disordered phase Ln0.90Ba0.10MnO3+δ.It is shown that the magnetic properties of the materials are determined by the joint action of chemical(cation ordering)and external(surface tension)pressures.

Comprehensive investigation of structural,dielectric and local piezoelectric properties of KNN ceramics

In this research paper,we utilized the traditional high-temperature solid-state reaction method to fabricate the K_(0.495)Na_(0.520)NbO_(3),K_(0.480)Na_(0.535)NbO_(3)and K_(0.475)Na_(0.540)NbO_(3)(abbreviated as KNN-1,KNN-2,and KNN-3,respectively)lead-free ion deficient ceramics for understanding the influence of ionic deficiency on the crystalline structure and dielectric/piezoelectric properties of the samples.X-ray diffraction patterns of these samples exhibited a perovskite tetragonal phase.Dielectric anomalies around 287℃and 471℃were identified as ferroelectric to ferroelectric and ferroelectric to paraelectric-transition temperatures for KNN-2 at 1 kHz.It was found that the composition KNN-2 exhibit relatively high Curie temperature i.e.,471℃.The conductivity plots confirm that the activation energies are frequency-dependent.The impedance behavior in our ceramic samples can be analyzed with the bulk/grain effect.The slope of Z′with temperature shows negative temperature coefficient of resistance(NTCR)type behavior in proposed KNN ceramics material.