Microstructures and microwave dielectric properties of (Ba1-xSrx)4(Sm0.4Nd0.6)28/3Ti18O54 solid solutions

(Ba 1x Sr x )4(Sm0.4 Nd 0.6)28/3 Ti 18 O 54(x = 0.02， 0.04， 0.06， 0.08， 0.1 ) 稳固的解决方案被准备由常规固态反应过程。它被发现那(Ba 1x Sr x )4(Sm0.4 Nd 0.6)28/3 Ti 18 O 54 陶艺充分由 BaSm 2 Ti 4 O 12 和乐队 2 Ti 5 为所有作文的 O 14 阶段。增加的 x 价值(0.02 x 0.1 ) 在((Ba 1x Sr x )4(Sm0.4 Nd 0.6)28/3 Ti 18 O 54 陶艺不能仅仅获得高

Effects of thermal and electrical histories on structure and dielectric behaviors of(Li_(0.5)Nd_(0.5))^(2+)-modified(Bi_(0.5)Na_(0.5))TiO_(3)-BaTiO_(3) ceramics

The effect of thermal and electrical histories on structure and dielectric behaviors is studied using 0.95(Bi_(0.5)Na_(0.5))_(0.97)(Li_(0.5)Nd_(0.5))_(0.03)TiO_(3)-0.05BaTiO_(3)(abbreviated as BNTLN0.03-BT5)ceramic as a selected system.Subtle structure change caused by annealing treatment,and pronounced phase transition and domain switching by electrical poling,are observed to occur,respectively.The dielectric constant and its strong frequency dispersion in unpoled samples decrease evidently by electrical poling due to electric field-induced ordered domain.The high temperature Maxwell-Wagner relaxor behavior vanishes by annealing treatment due to the loss of electrical inhomogeneity with interface charging effects.Piezoelectric properties are improved evidently by annealing treatment at 900℃,implying a new appropriate method to improve piezoelectric properties.

Long-term outcomes and prognosis factors of vagus nerve stimulation in patients with refractory epilepsy

Background:Vagus nerve stimulation(VNS)is an effective treatment for patients with refractory epilepsy,yet with varied predictive factors and heterogeneous long-term outcomes.Adjustment of VNS parameters is critical for obtaining favorable efficacy.In this study,we aimed to investigate the long-term outcomes and the possible predictive factors of VNS in patients with refractory epilepsy.Methods:Eighty-six patients(59 males and 27 females)who underwent VNS implantation for treatment of refractory epilepsy between May 2016 and May 2017 at five Epilepsy Centers were enrolled.The clinical data,including sex,age at epilepsy onset,VNS implantation,epilepsy duration,seizure type,MRI findings,history of neurosurgical operations,and responder rate(responders were those with≥50%seizure reduction),were analyzed.Results:Four-year follow-up data were available for 76 patients(53 males and 23 females).The mean current intensity at the last follow-up was 1.8±0.3 mA(range:0.75–2.5 mA).The mean seizure reduction was 36.2%at 6 months,38.5%at 1 year,69.4%at 3 years,and 56.7%at 4 years.A favorable outcome of≥50%reduction in seizure frequency occurred in 40.0%of the patients at 6 months,55.9%at 1 year with 4 patients being seizure-free,63.2%at 3 years with 5 patients being seizure-free,and 68.4%at 4 years with 5 patients being seizure-free.Earlier onset age(P<0.001)and shorter duration(P=0.042)were associated with favorable prognosis.Compared with generalized tonicclonic seizures,tonic seizures had a favorable outcome(P=0.026).Twenty-three patients underwent neurosurgical operations before VNS implantation,and the responder rate was 60.9%at the last follow-up.Conclusions:VNS is an adjunctive and effective treatment for patients with refractory epilepsy who are not good candidates for surgical resection or have failed to respond to surgical treatment.The stimulation efficacy increases over time after implantation,and earlier exposure to VNS improves the prognosis.

Photocurrent density and electrical properties of Bi_(0.5)Na_(0.5)Ti0_(3)-BaNi_(0.5)Nb_(0.5)0_(3) ceramics

In this work,the (1-x)Bi_(0.5)Na_(0.5)TiO_(3)-xBaNi_(0.5)Nb_(0.5)O_(3)(BNT-BNN;0.00≤x≤ 0.20)ceramics were prepared via a high-temperature solid-state method.The crystalline structures,photovoltaic effect,and electrical properties of the ceramics were investigated.According to X-ray diffraction,the system shows a single perovskite structure.The samples show the normal ferroelectric loops.With the increase of BNN content,the remnant polarization(P_(r))and coercive field(E_(c))decrease gradually.The optical band gap of the samples narrows from 3.10 to 2.27 eV.The conductive species of grains and grain boundaries in the ceramics are ascribed to the double ionized oxygen vacancies.The open-circuit voltage(V_(∝))of ~15.7 V and short-circuit current(J_(sc))of ~1450 nA/cm^(2) are obtained in the 0.95BNT-0.05BNN ceramic under 1 sun illumination(AM1.5G,100 mW/cm^(2)).A larger V_(∝) of 23 V and a higher J_(sc) of 5500 nA/cm^(2) are achieved at the poling field of 60 kV/cm under the same light conditions.The study shows this system has great application prospects in the photovoltaic field.

Dielectric behaviors and relaxor characteristics in Bi_(0.5)Na_(0.5)TiO_(3)-BaTiO_(3) ceramics

Microstructure and dielectric behaviors of heating/cooling and bias-field were investigated in lead-free ceramics(1-x)Bi_(0.5)Na_(0.5)TiO_(3)-xBaTiO_(3)(BNT-xBT,x=0,0.02,0.04,0.06,0.08 and 0.10).The relaxor characters and the Vogel–Fulcher law of frequency-dependent dielectric properties were analyzed.Three dielectric anomalies with pronounced frequency dispersion at Td,a maximum dielectric with variable frequency-dispersion at Tm and a third Maxwell–Wagner-type relaxation over a wide temperature range in high-temperature region were observed.The significant dielectric thermal hysteresis,low barrier energy,high freezing temperature in heating process and the maximum dielectric tunability appeared in x=0.4 ceramic.