Low-firing and temperature stability regulation of tri-rutile MgTa_(2)O_(6)microwave dielectric ceramics

A glass frit containing Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)component was used to explore the low-temperature sintering behaviors and microwave dielectric characteristics of tri-rutile MgTa_(2)O_(6)ceramics in this study.The good low-firing effects are presented due to the high matching relevance between Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass and MgTa_(2)O_(6)ceramics.The pure tri-rutile MgTa_(2)O_(6)structure remains unchanged,and high sintering compactness can also be achieved at 1150℃.We found that the Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass not only greatly improves the low-temperature sintering characteristics of MgTa_(2)O_(6)ceramics but also maintains a high(quality factor(Q)×resonance frequency(f))value while still improving the temperature stability.Typically,great microwave dielectric characteristics when added with 2wt%Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass can be achieved at 1150℃:dielectric constant,ε_(r)=26.1;Q×f=34267 GHz;temperature coefficient of resonance frequency,τ_(f)=-8.7×10^(-6)/℃.

A novel Na_(1−x)K_(x)TaO_(3)perovskite microwave dielectric ceramic with high permittivity and high positive temperature coefficient

A novel Na_(1−x)K_(x)TaO_(3)(x=0,0.025,0.05,0.075,0.1,and 0.15)ceramic with high permittivity and high positive temperature coefficient was synthesized via the conventional solid-state method.All samples were determined to be pure phase orthorhombic NaTaO3 structure of space group Pmcn,and larger grain and lower porosity were observed after adding an appropriate amount of K+ions.The Q×f value is majored by the packing fraction and grain size,while the value ofτf is influenced by Ta–O bond valence.The Na_(0.95)K_(0.05)TaO_(3) ceramic possesses excellent dielectric properties ofεr=164.29,Q×f=9091 GHz(f=3.15 GHz),tanδ=3.46×10^(–4),τf=+809.52 ppm/℃,sintered at 1550℃.Compared with NaTaO_(3) ceramics,the Na_(1−x)K_(x)TaO_(3)ceramics prepared in this study demonstrate higher dielectric constants and higher positive temperature coefficients,which are promising for device miniaturization andτf compensators.

The latest process and challenges of microwave dielectric ceramics based on pseudo phase diagrams

The explosive process of 5G communication evokes the urgent demand of miniaturized and integrated dielectric ceramics filter It is a pressing need to advance the development of dielectric ceramics utilization of emerging technology to design new materials and understand the polarization mechanism.This review provides the summary of the study of microwave dielectric ceramics(MWDCs)sintered higher than 1000℃ from 2010 up to now,with the purpose of taking a broad and historical view of these ceramics and illustrating research directions.To date,researchers endeavor to explain the structure-property relationship of ceramics with multitude of approaches and design a new formula or strategy to obtain excellent microwave dielectric properties.There are variety of factors that impact the permittivity,dielectric loss,and temperature stability of dielectric materials,covering intrinsic and extrinsic factors.Many of these factors are often intertwined,which can complicate new dielectric material discovery and the mechanism investigation.Because of the various ceramics systems,pseudo phase diagram was used to classify the dielectric materials based on the composition.In this review,the ceramics were firstly divided into ternary systems,and then brief description of the experimental probes and complementary theoretical methods that have been used to discern the intrinsic polarization mechanisms and the origin of intrinsic loss was mentioned.Finally,some perspectives on the future outlook for high-temperature MWDCs were offered based on the synthesis method,characterization techniques,and significant theory developments.

Surface modification toward luminescent and stable silica-coated quantum dots color filter

A highly pixelated and luminescent silica-coated quantum dot color filter(QDCF)was achieved by surface conjugation with epoxy functional group.Epoxy-functionalized silica-coated quantum dots(QDs)can be thoroughly mixed with SU-8 photoresist up to 25 wt.%without aggregation.The quantum yield(QY)of the silica-coated QDCF can be significantly improved from 19.3%to 36.5%after epoxy treatment.The pristine QDCF experienced a 40%QY decrease,while the epoxied silica-coated QDCF maintained its luminescence even after irradiation(300 mW cm 2@450 nm)for over 25 days.The well-controlled epoxy cap plays a critical role in attaining the ideal optical properties of the QDCF.

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/℃.

Cell-cell contact-induced gene editing/activation in mammalian cells using a synNotch-CRISPR/Cas9 system

Dear Editor,The CRISPR system has been widely used for genome manipulation in various cells,tissues and whole organisms.Although an increasing variety of inducible CRISPR systems have been exploited for a variety of applications,such as chemical switch(Zetsche et al.,2015),photo switch(Shao et al.,2018)and solution ligand switch(Baeumler et al.,2017;Kipniss et al.,2017;Schwarz et al.,2017)systems,a cell-cell interaction inducible system is absent.The synthetic Notch(synNotch)receptor is a recently developed cell-cell contact sensing platform,which contains a customized extracellular sensor module,a transmembrane core domain of native Notch,and a customized intracellular responder module(Morsut et al.,2016).

Influence of Re-ions with different ionic radius in Ba_(12)ReNb_(9)O_(36) on crystal structure and microwave dielectric properties

The Ba_(12)ReNb_(9)O_(36)(Re=Yb,Ce,Tm,Er,Y,Ho,Dy,Gd)ceramics are synthesized by solid-phase reaction method.The phase composition,crystal structure,microstructure,and microwave dielectric properties of the ceramics are investigated by X-ray diffraction,X-ray photoelectron spectroscopy,Scanning electron microscopy and Raman spectrum.The optimal microwave dielectric properties(ε_(r)=37.23,Q×f=36600 GHz,andτ_(f)=34 ppm/℃)are obtained for Ba_(12)YbNb_(9)O_(36) ceramic sintered at 1420℃for 6 h.In this system,the variation of dielectric constant is dominated by polarizability.The Q×f is mainly affected by internal strain/fluctuation of d-spacing.The variation of τ_(f) is related to the temperature coefficient of dielectric constant and the oxygen octahedron distortion.Furthermore,the reduction of Ce^(4+) ions,the relative density,linear thermal expansion coefficient,and the second phase are also important factors affecting microwave dielectric properties.