Renbing Sun

Pyroelectric properties of Mn-doped 94.6Na0.5Bi0.5TiO3-5.4BaTiO3 lead-free single crystals

We investigated the pyroelectric properties of ⟨001⟩, ⟨110⟩, and ⟨111⟩-oriented Mn doped 94.6Na0.5Bi0.5TiO3-5.4BaTiO3 (94.6NBT-5.4BT) crystals. Among the above three crystallographic orientations, the ⟨111⟩-oriented crystals possess the highest pyroelectric coefficients and the largest figures of merit. At 20 °C, the values of p, Fv, and Fd reach as high as 5.88 × 10−4 C/m2 K, 29.8 μPa−1/2, and 0.08 m2/C for ⟨111⟩-oriented crystals, respectively, which are superior to other lead-free ferroelectric materials. The crystals also demonstrate a high depolarization temperature and relatively stable thermal pyroelectric property. These results indicate the potential of Mn-doped 94.6NBT-5.4BT crystals for lead-free infrared pyroelectric detectors.

Growth and orientation dependence of electrical properties of 0.92Na0.5Bi0.5TiO3-0.08 K0.5Bi0.5TiO3 lead-free piezoelectric single crystal

A 0.92Na0.5Bi0.5TiO3-0.08 K0.5Bi0.5TiO3 (0.92NBT-0.08KBT) lead-free piezoelectric single crystal with dimensions of Φ 35 × 10 mm was successfully grown by the top-seeded solution growth method. The effective segregation coefficient for K was calculated to be 0.27. An x-ray powder diffraction measurement showed that the as-grown crystal possesses a rhombohedral perovskite structure at room temperature. The room-temperature dielectric constants for poled 〈001〉, 〈110〉, and 〈111〉 oriented crystal samples are found to be 683, 567, and 435 at 1 kHz, respectively. The (Tm, ɛm) values for 〈001〉, 〈110〉, and 〈111〉 oriented crystals are (316 °C, 4318), (317 °C, 4160), and (318 °C, 4348) at 1 kHz, which indicate that the dielectric parameters of the as-grown crystals show weaker anisotropy. The curves, ɛ(T), for the three crystallographic orientations show two anomalies at about 170 and 320 °C, respectively, relating to the ferroelectric-antiferroelectric phase and the antiferroelectric-paraelectric phase. There is a...

Microstructural, electrical and magnetoelectric properties of low-temperature sintering (Ni0.8Zn0.1Cu0.1)Fe2O4/[0.48PNN?0.02PZN?0.05PNW?0.45PT] composites

(1 − x)(Ni0.8Zn0.1Cu0.1)Fe2O4/x0.48Pb(Ni1/3Nb2/3)O3–0.02Pb(Zn1/3Nb2/3)O3–0.05Pb(Ni1/2W1/2)O3–0.45PbTiO3 ((1 − x)NZCF/xPNZNWT) magnetoelectric particulate ceramic composites were prepared by the conventional solid-state reaction method via a low-temperature sintering process. X-ray diffraction (XRD) measurements and scanning electron microscopy (SEM) observation confirm that ferrite and piezoelectric phases coexist in the sintered particulate composites. With the addition of sintering aids, densified ceramic composites can be prepared by the low-temperature sintering technique, which can improve the dielectric properties of the synthesized (1 − x)NZCF/xPNZNWT composites. The (1 − x)NZCF/xPNZNWT composites exhibit typical P–E hysteresis loops, where remnant polarization Pr decreases and coercive field Ec increases accompanied by the decrease of piezoelectric constant d33 with the increase of the ferrite phase incorporated into the composites. Although a magnetoelectric (ME) voltage coefficient of just 7.34 mV (cm Oe) − 1 is obtained in the 0.2NZCF/0.8PNZNWT composite, it is expected to be comparable to that of the reported bulk composites when the magnitude of the ac magnetic field increases and the frequency of the ac magnetic field increases to the resonant frequency of the piezoelectric phase.

GROWTH AND CHARACTERIZATION OF Na0.5Bi0.5TiO3–K0.5Bi0.5TiO3 LEAD-FREE PIEZOELECTRIC CRYSTAL BY THE TSSG METHOD

The 0.96Na0.5Bi0.5TiO3–0.04K0.5Bi0.5TiO3 (NKBT96/4) lead-free single crystal was successfully grown by top-seeded solution growth method. The effective segregation coefficient for K was calculated to be 0.20. X-ray powder diffraction measurement showed that the as-grown crystal possesses rhombohedral perovskite structure at room temperature. X-ray rock curve measure indicated that the as-grown single crystal owned relatively higher quality. The NKBT96/4 single crystal exhibits apparent diffused dielectric behavior, where the diffusiveness index α is 1.79 for the [001]-oriented crystal planes. A notable thermal hysteresis, ΔTh, of 25°C was disclosed for the tetragonal antiferroelectric-tetragonal paraelectric phase transition in the dielectric property studies between heating and cooling. The highest remnant polarization, Pr, 16.8 μC/cm2, was obtained at 100°C. The electromechanical coupling coefficient kt of the [001]-oriented crystal planes at room temperature was determined to be 38% using resonance–antiresonance technique. The room temperature piezoelectric constant d33 reaches 120 pC/N.