Xifa Long

A ferroelectric inorganic–organic hybrid based on NLO-phore stilbazolium

A ferroelectric inorganic–organic hybrid based on in situ substituted stilbazolium cation (TAMS2+ = trimethylamino-N-methyl stilbazolium) has been obtained. Single-crystal X-ray structure analysis demonstrates that the NLO-phore organic component of the complex is embedded into the inorganic polymeric [Bi2Cl8]2− framework and shows a polar arrangement with the cooperation of the nonsymmetric inorganic component. The measurement of ferroelectric and nonlinear optical properties show typical ferroelectricity and second harmonic generation (SHG) responses as well as a significant improvement of the laser damage threshold and thermal stability of relative organic material.

A Series of New Infrared NLO Semiconductors, ZnY6Si2S14, AlxDy3(SiyAl1−y)S7, and Al0.33Sm3SiS7

Four new quaternary isostructural rare-earth thiosilicates, ZnY(6)Si(2)S(14) (1), Al(0.50)Dy(3)(Si(0.50)Al(0.50))S(7) (2), Al(0.38)Dy(3)(Si(0.85)Al(0.15))S(7) (3), and Al(0.33)Sm(3)SiS(7) (4), crystallized in the chiral and polar space group P6(3), have been prepared by a facile synthetic routine. Compounds 1-3 show strong second harmonic generation effects at 2.1 um with the intensities of 1, 2, and 3 being about 2, 2, and 1 times that of KTP (KTiOPO(4)), respectively. The calculated band structure of 1 implies that the optical absorptions of BLn(6)M(2)Q(14) and ALn(3)MQ(7) family compounds are mainly ascribed to the charge transitions from Q-p to Ln-4f (4d for Y) states. Compounds 2-4 exhibit antiferromagnetic-like interactions.

Optically isotropic and monoclinic ferroelectric phases in Pb ( Zr 1 − x Ti x ) O 3 (PZT) single crystals near morphotropic phase boundary

We report the finding of unusual scale-dependent symmetry below the ferroelectric Curie temperature in the perovskite

Relaxor behavior in the solid solution between dielectric Ba(Mg1∕3Nb2∕3)O3 and ferroelectric PbTiO3

\text{Pb}({\text{Zr}}_{1\ensuremath{-}x}{\text{Ti}}_{x}){\text{O}}_{3}

Single Crystal Study of Competing Rhombohedral and Monoclinic Order in Lead Zirconate Titanate

single crystals of morphotropic phase boundary compositions. The crystals of tetragonal symmetry on submicrometer scale exhibit a macroscopic (optically determined) cubic symmetry. This peculiar optical isotropy is explained by the anomalously small size of tetragonal ferroelectric domains. Upon further cooling the crystals transform to the phase consisting of micrometer-sized domains of monoclinic symmetry.

Role of random electric fields in relaxors

Relaxor behavior has been found in the solid solution between complex perovskite Ba(Mg1∕3Nb2∕3)O3 (BMN) and ferroelectric PbTiO3 (PT), 0.4BMN-0.6PT, prepared by solid state reactions. A strong dispersion of the maximum dielectric permittivity (e′) appears around the temperature of Tm, which shifts towards higher temperatures with increasing frequency. The variation of Tm with frequency follows the Vogel-Fulcher relationship. The variation of 1∕e′ with temperature above Tm deviates from the Curie-Weiss law but satisfies a Lorentz-type function. The dielectric hysteresis loops are displayed at several temperatures which become slimmer at T>Tm. The remnant polarization gradually decreases with increasing temperature and persists up to above Tm.

Compositional disorder, polar nanoregions and dipole dynamics in Pb(Mg1/3Nb2/3)O3-based relaxor ferroelectrics

Neutron diffraction data obtained on single crystals of PbZr(1-x)Ti(x)O3 with x=0.325 and x=0.460, which lie on the pseudorhombohedral side of the morphotropic phase boundary, suggest a coexistence of rhombohedral (R3m/R3c) and monoclinic (Cm) domains and that monoclinic order is enhanced by Ti substitution. A monoclinic phase with a doubled unit cell (Cc) is ruled out as the ground state.

Optical study of Cr3+-doped LaSc3(BO3)(4) crystal

Significance Relaxors are characterized by a frequency-dependent peak in the dielectric permittivity and are critical to modern technological applications because they exhibit large dielectric constants and unparalleled piezoelectric coefficients. Despite decades of study a fundamental understanding of the origin of relaxor behavior is lacking. Here we compare the structural, dynamical, dielectric, and piezoelectric properties of two highly similar piezoelectric lead-oxide materials: ferroelectric PbZr1–xTixO3 and relaxor Pb(Mg1/3Nb2/3)1–xTixO3. Random electric fields are implicated as the genesis of relaxor behavior, and the diffuse scattering associated with short-range polar order is identified as the order parameter. The piezoelectric response is found to be greatly amplified in crystals that display this diffuse scattering. PbZr1–xTixO3 (PZT) and Pb(Mg1/3Nb2/3)1–xTixO3 (PMN-xPT) are complex lead-oxide perovskites that display exceptional piezoelectric properties for pseudorhombohedral compositions near a tetragonal phase boundary. In PZT these compositions are ferroelectrics, but in PMN-xPT they are relaxors because the dielectric permittivity is frequency dependent and exhibits non-Arrhenius behavior. We show that the nanoscale structure unique to PMN-xPT and other lead-oxide perovskite relaxors is absent in PZT and correlates with a greater than 100% enhancement of the longitudinal piezoelectric coefficient in PMN-xPT relative to that in PZT. By comparing dielectric, structural, lattice dynamical, and piezoelectric measurements on PZT and PMN-xPT, two nearly identical compounds that represent weak and strong random electric field limits, we show that quenched (static) random fields establish the relaxor phase and identify the order parameter.

Growth and spectroscopic properties of Cr3+-doped LaSc3(BO3)4

Abstract The complex structure of relaxor ferroelectrics comprises polar nanoregions (PNRs) which appear upon cooling below the Burns temperature and quenched compositional (chemical) disorder. The relation between the polar nanostructure and compositionally ordered regions (CORs) often observed in relaxors has been the subject of extensive theoretical investigations; however, the experimental data, especially concerning Pb(B′1/3B″2/3)O3-type complex perovskite relaxors, are rather limited. In this paper, we analyse and discuss the results of our recent investigations of the morphology of CORs and the dynamics of PNRs in Pb(Mg1/3Nb2/3)O3 based solid solutions in which the degree of compositional disorder was varied by means of changing the composition and/or by means of high-temperature annealing. The samples were characterised using X-ray diffraction, transmission electron microscopy, piezoresponse force microscopy, Brillouin light scattering, dielectric spectroscopy, as well as by measuring pyroelectric effect and ferroelectric hysteresis loops. No influence of the size of CORs on the PNRs relaxation in the ergodic relaxor phase is found. Instead, the CORs size influences significantly the diffuseness of the transition from the field-induced ferroelectric phase to the ergodic relaxor state. The results are interpreted in the framework of a model suggesting the coexistence of static and dynamic PNRs in the ergodic relaxor phase.

Structural Heterogeneity and Diffuse Scattering in Morphotropic Lead Zirconate-Titanate Single Crystals

This paper reports on the optical properties of Cr3+-doped LaSc3(BO3)4 (Cr3+:LSB). Based on measurement of the absorption spectrum the crystal field strength Dq, the Racah parameters B and C were calculated. The photoluminescence spectrum of Cr3+:LSB via 4T2→4A2 transition is a broadband emission from 740 to 1280 nm at room temperature. The measurements of absorption and photoluminescence spectra show that in Cr3+:LSB the Cr3+ ions occupy weak crystal field sites.