Hong-ling Zhang

Charge-discharge properties of lead zirconate stannate titanate ceramics

The charge-discharge properties of lanthanum- and niobium-doped lead zirconate stannate titanate ceramics were investigated by directly measuring the hysteresis loops, dielectric constants under a dc bias field, and pulse discharge current-time curves after varying charge-discharge circulations. It was found that there was no significant effect of the charge-discharge circulation on these properties. The first pulse current peak reached 1.8 kA at 40 kV/cm, and most of the stored charge was released in 500 ns. These results show that the obtained slanted ceramics with high energy density can withstand hundreds of charge-discharge circulations and are very promising for pulse capacitor applications.

Reversible pyroelectric response in Pb0.955La0.03(Zr0.42Sn0.40Ti0.18)O3 ceramics near its phase transition

Phase transition and pyroelectric behaviors of Pb0.955La0.03(Zr0.42Sn0.40Ti0.18)O3 (PLZST) ceramics were investigated as functions of temperature and electric field. Pyroelectric coefficient about 160×10−8 C cm−2 K−1 is detected at the electric-field-induce ferroelectric (FEIN) to antiferroelectric phase transition for the poled samples. Reversible pyroelectric response with a pyroelectric coefficient maximum about 50×10−8 C cm−2 K−1 is obtained when a dc bias is applied on the depoled sample simultaneously.

Poling temperature tuned electric-field-induced ferroelectric to antiferroelectric phase transition in 0.89Bi0.5Na0.5TiO3-0.06BaTiO3-0.05K0.5Na0.5NbO3 ceramics

We report the electric-field-induced ferroelectric (FEIN) to antiferroelectric (AFE) phase transition that is tuned by the poling temperatures in 0.89Bi0.5Na0.5TiO3-0.06BaTiO3-0.05K0.5Na0.5NbO3 (0.89BNT-0.06BT-0.05KNN) ceramics. Phase transition and pyroelectric behaviors of the ceramics were investigated as functions of temperature and electric field. Pyroelectric coefficient peaks of (3 ∼ 6.5) × 10−8 C cm−2 K−1 are detected at about 10 °C above the poling temperatures for the samples poled at different temperatures. The poling temperature tuned pyroelectric behaviors are attributed to the FEIN to AFE phase transition when the temperature increases.

Low thermal hysteresis pyroelectric response near the ferroelectric/antiferroelectric phase transition in Pb0.97La0.02(Zr0.42Sn0.40Ti0.18)O3 ceramics

The phase state of Pb0.97La0.02(Zr0.42Sn0.40Ti0.18)O3 (PLZST2) ceramics was studied by transmission electron microscopy analysis as well as polarization versus electric field (P-E) hysteresis loops. The initial state of this PLZST2 composition is ferroelectric (FE) and it transforms into antiferroelectric (AFE) as temperature increases. Change in polarization during this FE/AFE phase transition results in large pyroelectric response. A pyroelectric coefficient maximum about 220×10−8 C cm−2 K−1 is obtained for 3 kV/mm poled sample. Reversible pyroelectric response with large pyroelectric coefficient (>75×10−8 C cm−2 K−1) and low thermal hysteresis (<1.5 °C) is obtained under a dc bias of 0.6 kV/mm.

Dynamic hysteresis and scaling behavior for Pb(Zr,Ti)O3 ceramics

The dynamic hysteresis of Nb-doped Pb(ZrxTi1-x)O-3 (PZT, 0.40 against f and E-0 can be expressed with an identical form as proportional to f(0.01)E(0)(0.10) for either tetragonal phase or morphotropic phase, which is in good agreement with our previous result of rhombohedral PZT [Chen et al., J. Appl. Phys. 114, 244101 (2013)]. The results indicate that ferroelectrics with fairly distinct domain structures could have similar dynamic hysteresis and scaling behavior at high-E-0 region

Preparation of Cr2O3-based pigments with high NIR reflectance via thermal decomposition of CrOOH

Abstract In order to reduce greenhouse gas emission and urban heat island mitigation, pure and titanium(Ti)-doped Cr 2 O 3 cool pigments were prepared via the thermal decomposition of CrOOH. The result reveals that the pure Cr 2 O 3 pigment presents both a high near-infrared reflectance and excellent yellowish-green color. Meanwhile, titanium was doped to improve the NIR reflectance and strengthen the color. The color of the designed pigments was brighter, and most importantly, the NIR reflectance increased from 84.04% to 91.25% with increasing Ti content from 0 to 0.006% (mole fraction). However, excessive doping of Ti 4+ for Cr 3+ in Cr 2 O 3 ( x (Ti)≤0.008%) decreased the NIR reflectance. One possible reason is that the conductivity type of the Cr 2− x Ti x O 3+ δ changed from p-type conduction to n-type conduction with increasing Ti content, accompanied by the change of the electrical resistivity and the NIR reflectance. The prepared yellowish-green Cr 2 O 3 pigments have a great potential for extensive applications in construction and military.

Investigation on the Phase Transition Behaviors in Pb0.97La0.02(Zr0.42Sn0.40Ti0.18)O3 Ceramics

Phase transition behaviors in Pb0.97La0.02(Zr0.42Sn0.40Ti0.18)O3 (PLZST) ceramics were investigated by means of polarization, pyroelectric and dielectric studies. The polarization analysis indicated that the initial state of this PLZST ceramics is ferroelectric (FE) and it transforms into a narrow antiferroelectric (AFE) phase when the temperature approaches 120°C. This phase transition behavior was further confirmed by the pyroelectric and dielectric measurements. What is more, after poled, the frequency dispersion in dielectric constant (ϵ) and dissipation factor (tanδ) induced by La modification disappeared.

Identical scaling behavior of saturated dynamic hysteresis in rhombohedral lead zirconate titanate bulk ceramics

The scaling behaviors of dynamic hysteresis were investigated in serial rhombohedral Nb-doped Pb(Zr1-xTix)O-3 (PZT) bulk ceramics as a function of frequency (f) and field amplitude (E-0). Three distinct regions were plotted including linear loops, minor loops, and saturated loops with an increase of E-0. When the external fields were over similar to 1.5 times of coercive field (E-c), the scaling relations of saturated loops for these PZT ceramics could be expressed with an identical form as hysteresis area proportional to f(0.01)E(0)(0.10), which indicated that similar ferroelectric systems with different compositions could display a uniform scaling law under high-E-0 and low-f regions

Investigation of Reaction Mechanism on the Lime-Free Roasting of Chromium-Containing Slag

The lime-free roasting process of trivalent chromium-containing slag was investigated. The effect of Fe and liquid phase on the conversion reaction of chromium was discussed. The oxidation of trivalent chromium depends greatly on the diffusion of Na+ and O2. Both the raw material Na2CO3 and the intermediate product NaFeO2 serve as the carriers of Na+. The Na+ diffusion is improved by the binary liquid phase of Na2CrO4-Na2CO3, whereas excess liquid phase results in a low conversion rate of chromium by hindering the diffusion of oxygen towards the reaction interface. With the increasing of liquid volume, the controlled step of chromium oxidation changes from Na+ diffusion to oxygen diffusion. The mechanism study showed that the volume of liquid phase increased while raising the reaction temperature or prolonging the reaction time. Based on the role of both liquid phase and Fe, the oxidation process of chromium was summarized as a three-stage model: the Na+ diffusion-controlled stage, the O2 diffusion-controlled stage, and the oxidation reaction halted stage.

Effect of Sn:Ti ratio on electric properties in lead lanthanum zirconate stannate titanate ceramics

ABSTRACT The effect of Sn:Ti ratio with large range from 55:3 to 10:48 on the phase structure and electrical properties of Pb0.97La0.02(Zr0.42Sn0.58-xTix)O3 ceramics has been investigated. A sequence of phase transitions were analyzed by the variation of P-E hysteresis loops with increasing temperature. The antiferroelectric (AFE)/ferroelectric (FE) occurred at room temperature (RT) when Sn:Ti ratio is between 50:08 and 40:18 with the Zr content of 0.42, which improves the lanthanum doped ternary phase diagram.