Optically Isotropic and Monoclinic Ferroelectric Phases in PZT Single Crystals near Morphotropic Phase Boundary

We report the finding of unusual scale-dependent symmetry below the ferroelectric Curie temperature in the perovskite Pb(Zr1-xTix)O3 single crystals of morphotropic phase boundary compositions. The crystals of tetragonal symmetry (from x-ray diffraction experiments) on sub-micrometer 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 Cm symmetry.Comment: 7 pages, 3 figure

Giant Second-Harmonic Generation Response and Large Band Gap in the Partially Fluorinated Mid-Infrared Oxide RbTeMo2O8F

Strong second-harmonic generation (SHG) and a wide band gap are two crucial but often conflicting parameters that must be optimized for practical nonlinear optical (NLO) materials. We report herein the first d0-transition-metal (TM) tellurite with half of the d0-TM-octahedra partially fluorinated, namely, quinary RbTeMo2O8F, which exhibits giant SHG responses (27 times that of KH2PO4 (KDP) and 2.2 times that of KTiOPO4 (KTP) with 1064 and 2100 nm laser radiation, respectively), the largest SHG values among all reported metal tellurites. RbTeMo2O8F also possesses a large band gap (3.63 eV), a wide optical transparency window (0.34-5.40 μm), and a significant birefringence (Δn = 0.263 at 546 nm). Theoretical calculations and crystal structure analysis demonstrate that the outstanding SHG responses can be definitively attributed to the uniform alignment of the polarized [MoO5F]/[MoO6] octahedra and the seesaw-like [TeO4], and the consequent favorable summative polarization of the three distinct SHG-active polyhedra, both induced by partial fluorine substitution on the [MoO6] octahedra.This research was financially supported by National Natural Science Foundation of China (no. 51432006), Ministry of Education of China for Changjiang Innovation Research Team (no. IRT14R23), Ministry of Education and State Administration of Foreign Experts Affairs for 111 Project (no. B13025), and the Innovation Program of Shanghai Municipal Education Commission. M.G.H. thanks the Australian Research Council for support (DP170100411)

Giant Optical Anisotropy in the UV-Transparent 2D Nonlinear Optical Material Sc(IO3 )2 (NO3 )

Birefringence is a fundamental optical property for linear and nonlinear optical (NLO) materials. Thus far, it has proved to be very difficult to engineer large birefringence in optical crystals functioning in the UV region. Herein, we report the first 2D rare-earth iodate-nitrate crystal Sc(IO3)2 (NO3) (SINO), which is shown to exhibit giant optical anisotropy. Air-stable SINO possesses a short UV absorption edge (298 nm), a strong NLO response (4.0 times that of benchmark KH2 PO4) for the nitrate family, and the largest birefringence (Δn=0.348 at 546 nm) of inorganic oxide optical crystals. The unusually large birefringence and NLO response can be attributed to an optimized 2D layered structure, combined with highly polarizable and anisotropic building units [IO3]- and [NO3]-. These findings will facilitate the development of UV linear and NLO materials with giant optical anisotropy and promote their potential application in optoelectronic devices.This research was financially supported by the National Natural Science Foundation of China (no. 51432006), the Ministry of Education of China for the Changjiang Innovation Research Team (no. IRT14R23), the Ministry of Education and the State Administration of Foreign Experts Affairs for the 111 Project (no. B13025), and the Innovation Program of Shanghai Municipal Education Commission. C.W. thanks the National and Shanghai Postdoctoral Program for Innovative Talents (nos. BX201800216 and 2018192). M.G.H. thanks the Australian Research Council for support (DP170100411)

UV Solar‐Blind‐Region Phase‐Matchable Optical Nonlinearity and Anisotropy in a π‐Conjugated Cation‐Containing Phosphate

Wide ultraviolet (UV) transparency, strong second-harmonic generation (SHG) response, and sufficient optical birefringence for phase-matching (PM) at short SHG wavelengths are vital for practical UV nonlinear optical (NLO) materials. However, simultaneously optimizing these properties is a major challenge, particularly for metal phosphates. Herein, we report a non-traditional π-conjugated cation-based UV NLO phosphate [C(NH2)3]6(PO4)2⋅3 H2O (GPO) with a short UV cutoff edge. GPO is SHG active at 1064 nm (3.8 × KH2PO4 @ 1064 nm) and 532 nm (0.3 × β-BaB2O4 @ 532 nm) and also possesses a significant birefringence (0.078 @ 546 nm) with a band gap >6.0 eV. The PM SHG capability of GPO can extend to 250 nm, indicating GPO is a promising UV solar-blind NLO material. Calculations and crystal structure analysis show that the rare coexistence of wide UV transparency, large SHG response, and optical anisotropy is due to the introduction of π-conjugated cations [C(NH2)3]+ and their favorable arrangement with [PO4]3− anions.This research was financially supported by the NationalNatural Science Foundation of China (nos. 51432006,52002276), the Ministry of Education of China for theChangjiang Innovation Research Team (no. IRT14R23), theInnovation Program of Shanghai Municipal Education Com-mission, and the Ministry of Education and the StateAdministration of Foreign Experts Affairs for the 111 Project(no. B13025). M.G.H. thanks the Australian Research Coun-cil for support (DP170100411)

Large Second-Harmonic Response and Giant Birefringence of CeF2(SO4) Induced by Highly Polarizable Polyhedra

Second-harmonic generation (SHG) response and birefringence are two critically important properties of nonlinear optical (NLO) materials. However, the simultaneous optimization of these two key properties remains a major challenge because of their contrasting microstructure requirements. Herein, we report the first tetravalent rare-earth metal fluorinated sulfate, CeF2(SO4). Its structure features novel net-like layers constructed by highly distorted [CeO4F4] polyhedra, which are further interconnected by [SO4] tetrahedra to form a three-dimensional structure. CeF2(SO4) exhibits the strongest SHG effect (8 times that of KH2PO4) and the largest birefringence for sulfate-based NLO materials, the latter exceeding the birefringent limit for oxides. Theoretical calculations and crystal structure analysis reveal that the unusually large SHG response and giant birefringence can be attributed to the introduction of the highly polarizable fluorinated [CeO4F4] polyhedra as well as the favorable alignment of [CeO4F4] polyhedra and [SO4] tetrahedra. This research affords a new paradigm for the designed synthesis of high-performance NLO materials.This research was financially supported by the National Natural Science Foundation of China (no. 51432006), the Ministry of Education of China for the Changjiang Innovation Research Team (no. IRT14R23), the Ministry of Education and the State Administration of Foreign Experts Affairs for the 111 Project (no. B13025), the Innovation Program of Shanghai Municipal Education Commission, and the National and Shanghai Postdoctoral Program for Innovative Talents (nos. BX201800216 and 2018192). M.G.H. thanks the Australian Research Council for support (DP170100411)

Ferroelectricity and magnetism in Pb(Fe0.5Nb0.5)O3–Pb(Yb0.5Nb0.5)O3–PbTiO3 single crystals

Domain structure, ferroelectric and magnetic properties of [001]-oriented multiferroic single crystals Pb(Fe0.5Nb0.5)O3–Pb(Yb0.5Nb0.5)O3–PbTiO3 (PFN–PYN–PT) with various compositions were investigated with the purpose of understanding the ferroelectric and magnetic order. The samples were determined to be rhombohedral phase or coexistence of tetragonal and rhombohedral phases by means of X-ray diffraction analysis and optical study. Furthermore, the domain configuration in tetragonal phase always takes on 90° domain wall. All samples exhibit well-developed saturated hysteresis loop, indicating no substantial increase of conductivity despite the introduction of Fe3+ ions. But the piezoelectric coefficients were reduced due to the introduction of PFN. In addition, the PFN–PYN–PT single crystals showed paramagnetic behavior, resulting from the –O–Fe3+–O–Nb/Yb/Ti–O–Fe3+–O– magnetic interaction. Interestingly, M–H hysteresis loops display a magnetic relaxor behavior

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

This paper reports the growth and optical properties of Cr3+-doped LaSc3(BO3)(4) (Cr3+ :LSB). The Cr3+ -doped LaSc3(BO3)(4) crystal with dimension null set 25 x 35 mm(3) was obtained by Czochralski method. The absorption and photoluminescence spectra have been measured. The dominant features of absorption spectrum are two broadbands at ca. 400-700 nm. A broad emission band extending from 740 to 1280 nm with a peak at near 960 nm was observed. The lifetime of Cr3+ :LSB was 15 mus. (C) 2002 Elsevier Science B.V. All rights reserved

Preparation and Characterization of Lead-Free (K0.5Na0.5)NbO3-LiNbO3 and (K0.5Na0.5)NbO3-LiTaO3 Ferroelectric Single Crystals

Lead-free (K0.5Na0.5)NbO3-LiNbO3 (KNN-LN) and (K0.5Na0.5)NbO3-LiTaO3 (KNN-LT) ferroelectric single crystals, with the dimensions of 11 ´ 11 ´ 5 mm3 and 5 ´ 5 ´ 3 mm3, were grown successfully using the top-seeded solution growth (TSSG) method, respectively. The crystal structures were analyzed by means of X-ray diffraction, showing orthorhombic symmetry for KNN-LN single crystals and coexistence of orthorhombic and tetragonal symmetry for KNN-LT single crystals at room temperature. The orthorhombic-tetragonal (TO-T) and tetragonal-cubic (TC) phase transition temperatures are 195 °C and 420 °C for the KNN-LN single crystals, and 130 °C and 280 °C for KNN-LT single crystals, respectively. The remnant polarization (Pr) is 27.8 μC/cm2 with a coercive field (Ec) of 17 kV/cm for KNN-LT single crystals. The two single crystals showed 90° domains with layers in (parallel) straight lines, while KNN-LT single crystals have a larger domain region. The actual stoichiometry deviates easily from the original composition in the process of crystal growth, thus, an appropriate nominal composition and optimized crystal growth method is desired to get high-quality crystals in the future

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

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 T-4(2) -->(4)A(2) 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