44 research outputs found
Monoclinic phase in the relaxor-based piezo-/ ferroelectric Pb(MgNb-PbTiO system
A ferroelectric monoclinic phase of space group ( type) has been
discovered in 0.65Pb(MgNb-0.35PbTiO by means of high
resolution synchrotron X-ray diffraction. It appears at room temperature in a
single crystal previously poled under an electric field of 43 kV/cm applied
along the pseudocubic [001] direction, in the region of the phase diagram
around the morphotropic phase boundary between the rhombohedral (R3m) and the
tetragonal (P4mm) phases. The monoclinic phase has lattice parameters a = 5.692
A, b = 5.679 A, c = 4.050 A and = , with the b-axis
oriented along the pseudo-cubic [110] direction . It is similar to the
monoclinic phase observed in PbZrTiO, but different from that
recently found in Pb(ZnNb-PbTiO, which is of space
group ( type).Comment: Revised version after referees' comments. PDF file. 6 pages, 4
figures embedde
Phase diagram of the ferroelectric-relaxor (1-x)PbMg(1/3)Nb(2/3)O3-xPbTiO3
Synchrotron x-ray powder diffraction measurements have been performed on
unpoled ceramic samples of (1-x)PbMg(1/3)Nb(2/3)O3-xPbTiO3 (PMN-xPT) with 30%<=
x<= 39% as a function of temperature around the morphotropic phase boundary
(MPB), which is the line separating the rhombohedral and tetragonal phases in
the phase diagram. The experiments have revealed very interesting features
previously unknown in this or related systems. The sharp and well-defined
diffraction profiles observed at high and intermediate temperatures in the
cubic and tetragonal phases, respectively, are in contrast to the broad
features encountered at low temperatures. These peculiar characteristics, which
are associated with the monoclinic phase of MC-type previously reported by Kiat
et al and Singh et al., can only be interpreted as multiple coexisting
structures with MC as the major component. An analysis of the diffraction
profiles has allowed us to properly characterize the PMN-xPT phase diagram and
to determine the stability region of the monoclinic phase, which extends from
x= 31% to x= 37% at 20 K. The complex lansdcape of observed phases points to an
energy balance between the different PMN-xPT phases which is intrinsically much
more delicate than that of related systems such as PbZr(1-x)TixO3 or
(1-x)PbZn(1/3)Nb(1/3)O3-xPbTiO3. These observations are in good accord with an
optical study of x= 33% by Xu et al., who observed monoclinic domains with
several different polar directions coexisting with rhombohedral domains, in the
same single crystal.Comment: REVTeX4, 11 pages, 10 figures embedde
Development of Ferroelectric Order in Relaxor (1-x)Pb(Mg1/3Nb2/3)O3 - xPbTiO3
The microstructure and phase transition in relaxor ferroelectric
Pb(Mg1/3Nb2/3)O3 (PMN) and its solid solution with PbTiO3 (PT), PMN-xPT, remain
to be one of the most puzzling issues of solid state science. In the present
work we have investigated the evolution of the phase symmetry in PMN-xPT
ceramics as a function of temperature (20 K < T < 500 K) and composition (0 <=
x <= 0.15) by means of high-resolution synchrotron x-ray diffraction.
Structural analysis based on the experimental data reveals that the
substitution of Ti^4+ for the complex B-site (Mg1/3Nb2/3)^4+ ions results in
the development of a clean rhombohedral phase at a PT-concentration as low as
5%. The results provide some new insight into the development of the
ferroelectric order in PMN-PT, which has been discussed in light of the
kinetics of polar nanoregions and the physical models of the relaxor
ferroelectrics to illustrate the structural evolution from a relaxor to a
ferroelectric state.Comment: Revised version with updated references; 9 pages, 4 figures embedde
A chimerical phagocytosis model reveals the recruitment by Sertoli cells of autophagy for the degradation of ingested illegitimate substrates
Phagocytosis and autophagy are typically dedicated to degradation of substrates of extrinsic and intrinsic origins respectively. Although overlaps between phagocytosis and autophagy were reported, the use of autophagy for ingested substrate degradation by nonprofessional phagocytes has not been described. Blood-separated tissues use their tissue-specific nonprofessional phagocytes for homeostatic phagocytosis. In the testis, Sertoli cells phagocytose spermatid residual bodies produced during germ cell differentiation. In the retina, pigmented epithelium phagocytoses shed photoreceptor tips produced during photoreceptor renewal. Spermatid residual bodies and shed photoreceptor tips are phosphatidylserine-exposing substrates. Activation of the tyrosine kinase receptor MERTK, which is implicated in phagocytosis of phosphatidylserine-exposing substrates, is a common feature of Sertoli and retinal pigmented epithelial cell phagocytosis. The major aim of our study was to investigate to what extent phagocytosis by Sertoli cells may be tissue specific. We analyzed in Sertoli cell cultures that were exposed to either spermatid residual bodies (legitimate substrates) or retina photoreceptor outer segments (illegitimate substrates) the course of the main phagocytosis stages. We show that whereas substrate binding and ingestion stages occur similarly for legitimate or illegitimate substrates, the degradation of illegitimate but not of legitimate substrates triggers autophagy as evidenced by the formation of double-membrane wrapping, MAP1LC3A-II/LC3-II clustering, SQSTM1/p62 degradation, and by marked changes in ATG5, ATG9 and BECN1/Beclin 1 protein expression profiles. The recruitment by nonprofessional phagocytes of autophagy for the degradation of ingested cell-derived substrates is a novel feature that may be of major importance for fundamentals of both apoptotic substrate clearance and tissue homeostasis
High Performance and High Current Integrated Inductors using a Double Ultra Thick Copper Module in an Advanced 65 nm RF CMOS Technology
International audienc
High Performance and High Current Integrated Inductors using a Double Ultra Thick Copper Module in an Advanced 65 nm RF CMOS Technology
International audienc
Characterization and modeling of nonlinear trapping effects in power SiC MESFETs
International audienceno abstrac
High Performance 15-V Novel LDMOS Transistor Architecture in a 0.25µm BiCMOS Process for RF Power Applications.
International audienc
Dc and Low Frequency Noise analysis of hot-carrier induced degradation of low complexity 0.13 µm CMOS bipolar transistors
International audienc