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The correlation between the crystallization temperature and ferroelectric properties is studied by the measurements of impedance spectroscopy, activation energy, dielectric breakdown strength and dielectric constant in Na0.9K0.1NbO3 glass-ceramics, while different nucleating agents are added to optimize performance. It is found that the glass-ceramics crystallized at the temperatures of the second exothermic peak (about 900°C) have higher crystal degree, lager interface numbers and larger amount of bulk charges accumulated at the interfaces. However, the higher crystal degree of ferroelectric phase results in a lower value of resistivity and Ea which represent better charge spreading behavior. The better charge spreading behavior and drastic increase in the accumulation of bulk charge also result in low breakdown strength. The results show that the glass-ceramics heated at the temperature of first exothermic peak (about 700°C) with a reasonable crystal degree obtain higher energy storage density which is 1.94 J/cm3. [ABSTRACT FROM AUTHOR]

The role of a highly crystalline and oriented lead titanate ( PTO) seed layer on the subsequent phase and texture evolution of lead zirconate titanate ( PZT) thin films is investigated in situ using X-ray diffraction ( XRD) during crystallization. Crystalline PTO seed layers were first prepared via a 2-methoxyethanol route. Amorphous PZT with a Zr/Ti ratio of 52/48 was then deposited on the seed layer using the same synthesis route and subsequently crystallized in situ during XRD. During heating, a tetragonal-to-cubic transformation of the seed layer occurs prior to the formation of perovskite PZT. Subsequent nucleation of the crystalline PZT occurs in the cubic phase. Simultaneous to nucleation of PZT, development of a dominant 100 texture component was observed in the PZT phase of the thin films. The results indicate that 100 textured PTO nucleates 100 texture of PZT thin films during crystallization. [ABSTRACT FROM AUTHOR]

Electromechanical properties and high power characteristics of Pb-free hard piezoelectric ceramics in the (BiNa0.88K0.08Li0.04)0.5 (Ti1-xMnx)O3 (x = 0, 0.014, 0.015, and 0.016) system were studied. Mn doping resulted in a considerable enhancement of mechanical quality factor Qm and vibration velocity. The lowest mechanical and dielectric losses were achieved in 1.5 mol% Mn-doped ceramics with a planar Qm of about 970 and tanδ of 0.89%. The heat dissipation and resonance frequency shift under high drive condition were remarkably suppressed upon Mn doping. The maximum vibration velocity was increased from 0.28 m/s in undoped ceramic to 0.6 m/s in 1.5 mol% Mn-doped composition. The results of this study revealed that Mn-doped BNT-based piezoelectrics exhibited a superior high power performance compared to their lead-based counterparts such as PZT4 and PZT8 ceramics. [ABSTRACT FROM AUTHOR]

High piezoelectric properties are desired for lead-free piezoelectric materials in consideration as a replacement for lead-based materials in applications. Due to the high piezoelectric coefficient, ( Ba100− x Ca x) ( Ti100− y Zr y) O3 ( BCTZ) piezoelectric ceramics have been considered as a promising lead-free alternate piezoelectric material. Here, six compositions were selected based on a prediction that all the compositions would have high piezoelectric coefficient at room temperature. The results confirmed all compositions exhibit well developed hysteresis loops and a large piezoelectric coefficient at room temperature. This is due to the coexistence of several phases where the major phase is likely to be orthorhombic and the second phase is proposed to be tetragonal. The phase transition was found to occur over a broad temperature range instead of at a specific temperature only. A relationship between the tetragonal-orthorhombic phase transition temperature and Ca2+ and Zr4+ content was proposed. This enables clear determination of BCTZ compositions with high piezoelectric coefficient at a desired operation temperature. [ABSTRACT FROM AUTHOR]

The formation of a homogeneous Bi8 TiO14 phase was successfully achieved in a specimen calcined at 600°C. However, a Bi4 Ti3 O12 secondary phase also developed in specimens calcined at temperatures higher than 600°C, probably because of Bi2 O3 evaporation. For specimens sintered above 800°C, a small amount of the Bi8 TiO14 phase melted during sintering, with the liquid phase contributing to the densification of the specimens; however, Bi4 Ti3 O12 and Bi12 TiO20 secondary phases were still formed in these specimens. The microwave dielectric properties of the Bi8 TiO14 phase were considerably affected by variations in the microstructure of the specimens. When the sintering temperature exceeded 825°C, the amount of secondary phases increased, and this decreased the density and Q×f values of the specimens. Bi8 TiO14 ceramics sintered at 825°C exhibited promising microwave dielectric properties, with ε r = 47.4, Q×f = 5370 GHz, and τ f = −16.01 ppm/°C. [ABSTRACT FROM AUTHOR]

The (111) oriented plate-like BaTiO3 ( BT) particles with a tetragonal perovskite structure and a stoichiometric composition were successfully synthesized by a two-step molten-salt synthesis method ( MSS). The as-synthesized BT particles preserved the plate-like shape of precursor Ba6 Ti17 O40 ( B6 T17) particles with (001) major crystalline face, and, however, had a preferred pseudo-cubic (111) orientation. BT particle with a high aspect ratio (10-20 μm in diameter and <1.5 μm in thickness) was achieved as the soaking temperature and time were optimized to be 1170°C and 5 h, respectively. Oriented particulate layer X-ray diffraction analysis revealed that the crystallographic (001) plane of B6 T17 has a topotactic relation with the (111) plane of BT particles. [ABSTRACT FROM AUTHOR]

In this study, composition of ( Na0.5K0.5)NbO3 + x mol% CuO ceramics ( NKNC x, where x = 0-1 mol%) were separately prepared using the B-site oxide precursor method ( BO method) and the conventional mixed oxide method ( MO method). The diffracted angles of the NKNC x ceramics decreased as the concentrations of CuO dopants increased, because Nb5+ ions were replaced by Cu2+ ions, leading to the formation of oxygen vacancies. The microstructures of NKNC x ceramics prepared using the BO method were more homogeneous microstructures than that of ceramics prepared using the MO method. The mechanical quality factor ( Qm) and dielectric constant (ε33 T/ε0) of NKNC x ceramics prepared using the BO method were therefore by 21% and 25% better, respectively. The activation energy and internal bias field were measured and calculated to confirm the presence of oxygen vacancies. A low activation energy corresponds to a high Qm value. NKN ceramics with 0.75 mol% CuO doping prepared using the BO method had an activation energy and internal bias field of 0.95 eV and 3.5 kV/cm, respectively, at x = 0.75 mol%. The bulk density, kp, Qm, ε33 T/ε0, and dielectric loss of NKNC x ceramics with this composition were 4.488 g/cm3, 41.5%, 2100, 280, and 0.15%, respectively. [ABSTRACT FROM AUTHOR]