No abstract

No abstract

The discovery of lead-free piezoelectric materials is crucial for future information and energy storage applications. Enhanced piezoelectric and other physical properties are commonly observed near the morphotropic phase boundary (MPB) composition of ferroelectric solid solutions. The (1-x)Ba(Zr 0.2 Ti 0.8 )O 3 -x(Ba 0.7 Ca 0.3 )TiO 3 (BZT-xBCT) system exhibits a large electromechanical response around its MPB region at x=0.5. We report experimental and theoretical results of BZT-xBCT over a wide composition range (0.3≤x≤1.0). X-ray diffraction and Raman spectroscopy studies indicate a composition-induced structural phase transition from a rhombohedral (R3m) phase at x≤0.4 to a tetragonal (P4mm) phase at x≥0.6 through a multiphase coexistence region at 0.45≤x≤0.55 involving orthorhombic + tetragonal (Amm2+P4mm) phases. First-principles calculations elucidate the phase competition in the coexistence region. The critical composition (x= 0.5) displays enhanced dielectric, ferroelectric and piezoelectric properties, where notably d 33 ~ 320 pC/N. This work provides clear evidence of Amm2+P4mm crystallographic phases in the MPB region, which is responsible for the improved functional properties.

We report studies of the ferroelectric and magnetic phase transitions of (1 – x)­Pb­(Fe0.5Nb0.5)­O3 – xCo0.65Zn0.35Fe2O4 (x = 0.2) composite with emphasis upon the nature of magnetoelectric coupling at room temperature. The presence of all cationic elements with their required stoichiometry have been confirmed by SEM and XPS studies. The composite shows well-saturated ferroelectric and ferromagnetic (multiferroic) behavior at room temperature. A ferroelectric-paraelectric phase transition has been confirmed from the temperature dependent dielectric spectra along with DSC and Raman spectroscopic studies. Antiferromagnetic, ferromagnetic, and relaxor paramagnetic states have been observed in this composite. This composite shows strong bulk biquadratic magnetoelectric coupling at room temperature, which can be useful for potential multifunctional device applications.

No abstract