Thermal stable and ultralow dielectric loss in(Gd_(0.5)Ta_(0.5))_(x)Ti_(1-x)O_(2)giant permittivity ceramics by defect engineering

High dielectric loss and poor temperature stability are the current barriers to the application of dielectric materials.In present work,we synthesized a system of acceptor Gd^(3+)and donor Ta^(5+)co-doped(Gd_(0.5)Ta_(0.5))_(x)Ti_(1-x)O_(2)(GTTOx,x=0,0.01,0.02,0.04,0.06)ceramics to enhance dielectric response.It was found that a colossal permittivity(CP,2.65×10^(4)@1 kHz,2.37×10^(4)@1 MHz),a very low dielectric loss(tanδ,0.007@1 kHz,0.03@1 MHz),good stability of frequency(20–10^(6)Hz)and temperature(RT–250°C,Δε′(T)/ε′30<±15%,at 1 kHz)were achieved simultaneously in GTTO0.01 ceramic.Complex impedance spectroscopy,XPS,SEM,and Raman spectroscopy were used to investigate the reasons for the improved dielectric properties.The result indicated that the main reasons for CP and low dielectric loss are the synergistic effect of the electron pinning defect-dipole(EPDD)model,the internal blocking layer capacitance(IBLC)mechanism,and electrode response.This work provides a promising approach for the design of defect-related high-performance giant dielectric ceramics.

High efficiently harvesting visible light and vibration energy in(1−x)AgNbO_(3)-xLiTaO_(3) solid solution around antiferroelectric-ferroelectric phase boundary for dye degradation

Simultaneously employing light and vibration energy by piezoelectric material to realize environmental remediation is an advanced oxidation method.Silver niobate(AgNbO_(3))is a visible light driven photocatalyst for the removal of organic pollutants.However,the high recombination rate of photo-generated electrons and holes suppresses its photocatalytic activity.Piezoelectric potential excited by vibration can facilitate the separation of light induced charges.Unfortunately,AgNbO_(3) is an antiferroelectric.In this work,distinct photo-/vibration-bi-catalysis has been achieved in ferroelectric(1−x)AgNbO_(3)-xLiTaO_(3) solid solution.The results show that ~96% Rhodamine B(RhB)can be decomposed under the bi-excitation of ultrasound and visible light within 120 min with 0.95AgNbO_(3)-0.05LiTaO_(3) catalyst.The synergy effect from efficient visible light excitation and enhanced separation of the photo-induced charges from the electric field by the mechanical strain results in the distinct decomposition performance of catalysts.

Catalytic action of rare earth oxide(La_(2)O_(3),CeO_(2),Pr_(6)O_(11))on electrochemical oxidation of activated carbon in molten KOH-NaOH

The oxidation of anode carbon fuel directly affects the electrochemical performance of molten hydroxide direct carbon fuel cell(MHDCFC).In general,the anode carbon fuel can be oxidized at high temperature,thus the direct carbon fuel cell(DCFC)can show great electrochemical performance.In this study,rare earth oxides(La_(2)O_(3),CeO_(2),Pr_(6)O_(11))were prepared by the method of precipitation.Activated carbon was prepared by pretreatment of lignite.Rare earth oxides and activated carbon were mixed as anode carbon fuel,and rare earth oxides were used to catalyze the electrochemical oxidation of anode carbon fuel.The results show that CeO_(2)has better electrocatalytic activity compared with La_(2)O_(3)and Pr_(6)O_(11) in the MHDCFC.The electrochemical test results show that the current density(at 0.4 V)increases from 81.02 to 112.90 mA/cm^(2)and the maximum power density increases from 34.78 to 47.05 mW/cm^(2)at 450℃,when the mass fraction of CeO_(2)is increased from 0 to 40%.When the mass fraction of CeO_(2)is 30%,the current density(82.55 mA/cm^(2)at 0.4 V)at 400℃is higher than that(81.02 mA/cm^(2)at 0.4 V)without CeO_(2)at 450℃.The electrochemical oxidation mechanism of CeO_(2)catalyzed anode carbon fuel is discussed.