Structure,far-infrared spectroscopy,microwave dielectric properties,and improved low-temperature sintering characteristics of tri-rutile Mg_(0.5)Ti_(0.5)TaO_(4) ceramics

In this study,tri-rutile type Mg_(0.5)Ti_(0.5)TaO_(4) ceramics were synthesized,where the structure–property relationship,especially the structural configuration and intrinsic dielectric origin of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics,and the low-firing characteristics were studied.It is found that the tri-rutile structural type is unambiguously identified through the Rietveld refinement analysis,the selected area electron diffraction(SAED),and the high-resolution transmission electron microscopy(HRTEM)along the[110]zone axis.With the increase in sintering temperature,the densification and uniformity of crystal growth play important roles in regulating the microwave dielectric properties of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics.Intrinsically,theoretical dielectric properties calculated by the far-infrared reflective spectra approached the experimental values,indicating the importance of structural features to dielectric properties.Furthermore,a glass additive with high matching relevance with ceramics has been developed to decrease the high sintering temperature of Mg_(0.5)Ti_(0.5)TaO_(4) ceramics,where 2–4 wt%Li_(2)O–MgO–ZnO–B_(2)O_(3)–SiO_(2)(LMZBS)glass frit was adopted to reduce the suitable temperature from 1275 to 1050℃ without significantly deteriorating the microwave dielectric characteristics.Specifically,Mg_(0.5)Ti_(0.5)TaO_(4) ceramics containing 2 wt% glass addition sintered at 1050℃for 4 h possess excellent microwave dielectric properties:dielectric constant(ε_(r))=44.3,quality factor multiplied by resonant frequency(Q×f)=23,820 GHz(f=6.2 GHz),and the temperature coefficient of resonant frequency(τ_(f))=123.2 ppm/℃.

Co-doping strategy enhanced the ionic conductivity and excellent lithium stability of garnet-type Li_(7)La_(3)Zr_(2)O_(12)electrolyte in all solidstate lithium batteries

Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO)is one of the most promising solid-state electrolytes(SSEs).However,the application of LLZO is limited by structural instability,low ionic conductivity,and poor lithium stability.To obtain a garnet-type solid electrolyte with a stable structure and high ionic conductivity,a series of TaeCe co-doping cubic Li_(6.4)La_(3)Zr_(1.4-x)Ta_(0.6)Ce_(x)O_(12)(LLZTCO,x=,0.02,0.04,0.06,0.08,0.10,0.20,0.30)electrolytes were successfully synthesized through conventional solid-phase method.The Ta^(5+)doping can introduce more lithium vacancies and effectively maintain the stability of the cubic phase.The Ce^(4+)with a larger ionic radius is introduced into the lattice to widen the Lit migration bottleneck size,which significantly increased the ionic conductivity to 1.05×10^(-3)S/cm.It also shows excellent stability to lithium metal by the optimization of Lit transport channel.Li||LLZTCO||Li symmetric cells can cycle stably for more than 6000 h at a current density of 0.1 mA/cm^(2)without any surface modifications.The commercialization potential of LLZTCO samples in all solid-state lithium batteries(ASSLBs)is confirmed by the prepared LiFePO_(4)||LLZTCO||Li cells with a capacity retention rate of 98%after 100 cycles at 0.5C.This new co-doping method presents a practical solution for the realization of high-performance ASSLBs.

Low-firing,temperature stable and improved microwave dielectric properties of ZnO-TiO_(2)-Nb_(2)O_(5) composite ceramics

This article presents low-firing,low-loss and temperature stable ZnO-TiO_(2)-Nb_(2)O_(5) microwave dielectric composite ceramics with the assistance of lithium borosilicate(LBS)and zinc borosilicate(ZBS)glass frits.There is a liquid phase(eutectic mixture)generated by LBS(ZBS)glass,and solid particles could be wetted and dissolved.Therefore,the migrations and rearrangements of particles could be performed.Besides,compared with ceramics undoped with glass frits,lower activation energies(E_(a))of ceramics doped with LBS and ZBS glass suggest that the low-temperature sintering behavior is easier to carry out.The results indicated that LBS and ZBS glass both are effective sintering aids to accelerate the sintering process and improve the microwave dielectric properties of composite ceramics by controlling the phase compositions under low temperature.Combination great properties of ZnO-TiO_(2)-Nb_(2)O_(5) ceramics were obtained when sintered at 900℃ for 4 h:ε_(r)=36.7,Q×f=20,000 GHz,τ_(f)=7 ppm/℃.

Structure,dielectric and relaxor properties of Sr_(0.7)Bi_(0.2)TiO_(3)—K_(0.5)Bi_(0.5)TiO_(3)lead-free ceramics for energy storage applications

Sr_(0.7)Bi_(0.2)TiO_(3)(SBT)by increasing the proportion and size of polar nano-region.Meanwhile,the BDS remains a high level with x<0.38 attributed to the addition of KBT with a large band gap.As a result,the 0.62SBT-0.38KBT exhibits a high energy storage density of 2.21 J/cm^(3)with high h of 91.4%at 220 kV/cm and superior temperature stability(-55~150℃),frequency stability(10~500 Hz)and fatigue resistance(105 cycles).Moreover,high pulsed discharge energy density(1.81 J/cm^(3)),high power density(49.5 MW/cm3)and great thermal stability(20~160℃)are achieved in 0.62SBT-0.38KBT.Based on these excellent properties,the 0.62SBT-0.38KBT are suitable for pulsed power systems.This work provides a novel strategy and systematic study for improving energy storage properties of SBT.