ABSTRACT
This paper proposes a new method for cutoff probe using a nanosecond impulse generator and an oscilloscope, instead of a network analyzer. The nanosecond impulse generator supplies a radiating signal of broadband frequency spectrum simultaneously without frequency sweeping, while frequency sweeping method is used by a network analyzer in a previous method. The transmission spectrum (S21) was obtained through a Fourier analysis of the transmitted impulse signal detected by the oscilloscope and was used to measure the electron density. The results showed that the transmission frequency spectrum and the electron density obtained with a new method are very close to those obtained with a previous method using a network analyzer. And also, only 15 ns long signal was necessary for spectrum reconstruction. These results were also compared to the Langmuir probe's measurements with satisfactory results. This method is expected to provide not only fast measurement of absolute electron density, but also function in other diagnostic situations where a network analyzer would be used (a hairpin probe and an impedance probe) by replacing the network analyzer with a nanosecond impulse generator and an oscilloscope.
ABSTRACT
A low temperature, high yield hydrothermal route has been discovered for the phase-pure synthesis of the multiferroic BaMF(4) (M = Mg, Mn, Co, Ni, and Zn) family. The synthesis involves the use of CF(3)COOH instead of HF in an aqueous medium and, under the correct conditions, produces pure and polycrystalline BaMF(4). In addition to the synthetic description, second-harmonic generation, thermogravimetric, and differential scanning calorimetry data are presented.
ABSTRACT
A new noncentrosymmetric polar ternary tellurium(IV) oxide phosphate, Te(2)O(PO(4))(2), has been synthesized by a standard solid-state reaction, and the structure was determined by single crystal X-ray diffraction. The material shows a three-dimensional framework structure that is composed of slightly distorted TeO(5) square pyramids and PO(4) tetrahedra. Within the framework three-, four-, and seven-membered ring channels are observed along the [100] direction. In addition to structural characterization, second-harmonic generation (SHG) and piezoelectric measurements were performed. Powder SHG measurement on the Te(2)O(PO(4))(2), using 1064 nm radiation, indicated the material has a SHG efficiency of approximately 50 x alpha-SiO(2). Converse piezoelectric measurements revealed a d(33) value of 20 pm V(-1). Thermogravimetric analysis, UV-vis diffuse reflectance, and infrared spectroscopy were also performed, as were electronic structure calculations. Crystal data: Te(2)O(PO(4))(2), monoclinic, space group Cc (No. 9), with a = 5.3819(7) A, b = 13.6990(19) A, c = 9.5866(12) A, V = 686.73(16) A(3), and Z = 4.
ABSTRACT
A new organically templated noncentrosymmetric polar zinc chloride, [N(CH(3))(4)]ZnCl(3), has been synthesized hydrothermally, and the structure was determined by single crystal X-ray diffraction. The reported material exhibits a unidimensional crystal structure consisting of chains of anionic ZnCl(4) tetrahedra that are separated by [N(CH(3))(4)](+) cations. Second-harmonic generation (SHG) measurement on the noncentrosymmetric [N(CH(3))(4)]ZnCl(3), using 1064 nm radiation, indicate the material has a SHG efficiency of approximately 15 x alpha-SiO(2). Additional SHG measurements indicate the material is nonphase-matchable (type 1). In addition, converse piezoelectric measurements revealed d(33) values of 10 pm/V. Thermogravimetric analysis, UV-vis diffuse reflectance, and infrared spectroscopy were also performed, as were electronic structure calculations. Crystal data: [N(CH(3))(4)]ZnCl(3), orthorhombic, space group Pmc2(1) (No. 26), with a = 7.2350(14) A, b = 8.8210(18) A, c = 15.303(3) A, V = 976.6(3) A(3), and Z = 4.
ABSTRACT
We have synthesized a series of new alkali-metal or Tl(+) titanium iodates, A(2)Ti(IO(3))(6) (A = Li, Na, K, Rb, Cs, Tl). Interestingly the Li and Na phases are noncentrosymmetric (NCS) and polar, whereas the K, Rb, Cs, and Tl analogues are centrosymmetric (CS) and nonpolar. We are able to explain the change from NCS polar to CS nonpolar using cation-size arguments, coordination requirements, and bond valence concepts. The six materials are topologically similar, consisting of TiO(6) octahedra, each of which is bonded to six IO(3) polyhedra. These polyhedral groups are separated by the A(+) cations. Our calculations on Na(2)Ti(IO(3))(6) indicate that polarization reversal is energetically very unfavorable, rendering the material polar but not ferroelectric. For all of the materials, synthesis, structural characterization, electronic structure analysis, infrared spectra, UV-vis and thermogravimetric measurements, and ion-exchange reactions are reported. For the polar materials, second-harmonic generation, piezoelectricity, and polarization measurements were performed. Crystal data: Li(2)Ti(IO(3))(6): hexagonal, space group P6(3) (No. 173), a = b = 9.3834(11) A, c = 5.1183(6) A, Z = 1. Na(2)Ti(IO(3))(6): hexagonal, space group P6(3) (No. 173), a = b = 9.649(3) A, c = 5.198(3) A, Z = 1. K(2)Ti(IO(3))(6): trigonal, space group R3 (No. 148), a = b = 11.2703(6) A, c = 11.3514(11) A, Z = 3. Rb(2)Ti(IO(3))(6): trigonal, space group R3 (No. 148), a = b = 11.3757(16) A, c = 11.426(3) A, Z = 3. Cs(2)Ti(IO(3))(6): trigonal, space group R3 (No. 148), a = b = 11.6726(5) A, c = 11.6399(10) A, Z = 3. Tl(2)Ti(IO(3))(6): trigonal, space group R3 (No. 148), a = b = 11.4167(6) A, c = 11.3953(11) A, Z = 3.
ABSTRACT
A new polar noncentrosymmetric material, Li(2)Ti(IO(3))(6), has been synthesized and characterized. The material is built up from a TiO(6) octahedron that is linked to six IO(3) polyhedra. These polyhedral groups are separated by Li(+) cations. The Ti(4+) and I(5+) cations are in asymmetric polar coordination environments attributable to second-order Jahn-Teller effects. The distortion associated with the Ti(4+) cation is negligible, since the TiO(6) octahedra are completely surrounded by IO(3) polyhedra. The I(5+) cation is in a highly polar asymmetric coordination environment attributable to its stereoactive lone pair, which was qualitatively described by pseudopotential calculations of the electron localization function. The macroscopic polarity of Li(2)Ti(IO(3))(6) may be attributed to parallel alignment of the stereoactive lone pairs on the I(5+) cations. This parallel alignment profoundly influences the material's functional properties: second-harmonic generation, piezoelectricity, and pyroelectricity. The material is, however, not ferroelectric, as the polarization associated with I(5+) is not switchable.
ABSTRACT
Two new Sn2+-W6+-oxides, Sn2WO5 and Sn3WO6, have been synthesized hydrothermally, and their structures have been determined by single-crystal X-ray diffraction methods. Both materials exhibit layered structural topologies consisting of two edge-shared WO6 octahedra connected to SnO3 and SnO4 polyhedra. Both the W6+ and Sn2+ cations are in locally asymmetric coordination environments attributable to second-order Jahn-Teller effects. Infrared and Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, and thermogravimetric analysis were also performed on the reported materials. Theoretical calculations using the tight binding linear muffin tin orbital method agree with the observed electronic properties of these materials and indicate that the stereoactive lone pair on the Sn2+ is similar for both materials. Crystal data: Sn2WO5, monoclinic, space group P21/n (No. 14), a = 7.994(2) A, b = 13.712(4) A, c = 10.383(3) A, beta = 110.507(3) degrees , V = 1066.0(5) A3, and Z = 4; Sn3WO6, monoclinic, C2/c (No. 15), a = 12.758(3) A, b = 8.0838(16) A, c = 13.865(3) A, beta = 112.49(3) degrees , V = 1321.2(5) A3, and Z = 8.
