Hideo Koizumi

Ferroelectric and optical properties of Pb5Ge3O11 and its isomorphous compound Pb5Ge2SiO11

The temperature characteristics of dielectric constants, spontaneous polarization, thermal‐expansion coefficients, indices of refraction, and optical rotatory power of Pb5Ge3O11 single crystals have been investigated in detail from room temperature up to above the Curie temperature, 177°C. From the results of these measurements, the following constants were obtained: linear thermal‐expansion coefficients (αa)F=7.75×10−6/deg°C and (αc)F=7.79×10−6/deg°C (ferroelectric phase), (αa)P=13.8×10−6/deg°C and (αc)P=13.4×10−6/deg°C (paraelectric phase); quadratic electro‐optic constants g33T=0.47×108 cm4 /C2, g13T=0.37×108 cm4 /C2; and electrogyration coefficient γ33 =8.7 cm2/C. An isomorphous compound Pb5(Ge2O7)(SiO4) was synthesized and was found to be ferroelectric with T c=60°C and Ps=1.7 μC/cm2 at room temperature. Ferroelectric properties and electrogyration coefficient were studied in the solid‐solution system Pb5(Ge2O7)(GeO4)1−x (SiO4)x.

Crystal Structure of Cupric Benzoate Trihydrate Cu(C6H5COO)23H2O

Cupric benzoate trihydrate crystallizes in the monoclinic system, space group I 2/ c , with four formula units in a unit cell of dimensions, a =6.98, b =34.12, c =6.30 A; \(\beta{\doteqdot}90\)°. There are two kinds of benzoate groups. The carboxyl oxygen atoms of benzoate group I are in direct contacts with copper atoms, while those of group II are coordinated to copper atoms through water molecules. Each copper atom is situated at the center of a deformed octahedron consisted of four water molecules and two oxygen atoms from benzoate group I. The octahedra are linked, by sharing two water molecules, into a column parallel to the c -axis. Within this column, copper atoms lie on a line at an interval of 3.15 A, which suggests the presence of magnetic anisotropy.

Single crystals in the Bi2O3/1bMoO3 binary system: Growth and optical properties

Abstract Single crystals of Bi 2 O 3 ·3MoO 3 and 3Bi 2 O 3 ·2MoO 3 in the Bi 2 O 3 /1bMoO 3 binary system were grown by pulling from the melt. Single crystal Bi 2 O 3 ·MoO 3 (Bi 2 MoO 6 ), which is well known as Koechlinite, could not be grown successfully. A new compound 3Bi 2 O 3 ·2MoO 3 was found to melt congruently and to be easily grown from the melt. It belongs to the monoclinic crystal system with space group C 4 2h . Refractive indices of Bi 2 O 3 ·3MoO 3 and 3Bi 2 O 3 ·2MoO 3 were investigated.

Epitaxial growth of KNdP4O12 laser waveguides

Abstract The growth of KNdP 4 O 12 and KLaP 4 O 12 single crystals from an H 3 PO 4 solution was accomplished with an evaporation and condensation technique. Using the solution from which KNdP 4 O 12 can crystallize, a KNdP 4 O 12 single-crystal epitaxial waveguide layer was successfully deposited on as-grown KLaP 4 O 12 substrates in the same manner. The layer on the (001) plane exhibited a good epitacial waveguide, and a 28 μm thick KNdP 4 O 12 waveguide laser was obtained.

Temperature variations of lattice parameters of LiNbO3, LiTaO3 and Li (Nb 1−y Tay) O3 solid-solutions

Abstract Temperature variations of the lattice parameters a and c of LiNbO 3 , LiTaO 3 and their solid-solution crystals Li (Nb 1− y Ta y ) O 3 of y = 0.23, 0.40 and 0.73 have been determined with a high-temperature X-ray diffractometer in the temperature range between 25 and 1000°C.

Czochralski growth of Ag4P2O7 crystals

Abstract Ag4P2O7 crystals were grown by the Czochralski method. Ag4P2O7 melts congruently at 570°C and shows a phase transition at 350°C. It belongs to the trigonal system. Space groups are R 3 c in the high temperature phase and one of the four groups P31,12, P31 21 P3212 and P3221 in the low temperature phase. Lattice parameters are a H = 9.538 A and c H = 40.83 A at room temperature. In order to suppress the generation of cracks caused by the phase transition during the annealing after growth, the [210] direction was chosen parallel to the pulling direction. Electrical, electromechanical and optical properties were investigated.

An X-Ray Study on PbO-Nb2O5-TiO2 System

Ternary system PbO-Nb2O5-TiO2 was studied. Ceramic samples were prepared at 900°C and 1200°C in air, and analyzed by X-ray powder diffraction method. The phase diagrams for this system at the two sintering temperatures are constructed. The diagrams indicate that ternary compounds PbO-Nb2O5-TiO2 (PbNb2TiO8) and PbO-2Nb2O5-3TiO2 (PbNb4Ti3O17) exist, and that a pyrochlore type cubic compound phase extends from 3PbO-2Nb2O5 site toward TiO2-rich part of the system, covering a considerably wide region. Another single phase region near the TiO2 region has remained unidentified. The PbNb2TiO8 compound is found to be piezoelectric.

Photoinduced effect on the phase transition in Ag3VO4 thin films

Ag3VO 4 is one of the compounds in the A g 2 0 V 2 0 5 binary system. Unindexed X-ray powder diffraction data and the phase diagrams for an A g 2 0 V 2 0 5 system formulated above 350°C were reported by Fleury and Kohlmuller 1. Good photochromism in AgaVO 4 thin films has recently been reported 2. However, other physical properties have not yet been clarified. Accordingly, the present authors investigated their crystallographic properties and discovered a phase transition in Ag3VO 4 crystals and a photoinduced effect on the phase transition in the annealed thin films. Ag3VO4 crystal samples were synthesized by sintering a 3Ag20-V20 5 mixture at 400 °C for 6 h. Crystalline Ag3VO 4 thin films were prepared using the same method as described earlier 2. A phase transition was observed at about 100 °C in AgaVO 4 crystals by differential thermal analysis and X-ray diffraction. The crystal systems of the low temperature ~ phase and the high temperature 13 phase are monoclinic (a = 8.73 ~, b -6.71/~, c = 6.51 ~ and fl = 95.4 °) and orthorhombic (a = 8.75 ~, b = 6.71/~ and c = 6.56 ~) respectively. Table I shows the interplanar spaces, Miller indices and relative intensities for both phases. Figure 1 shows the thermal hysteresis accompanying the phase transition, where the content C a of the ~l phase is plotted against temperature. C a is calculated from the equation

LiBixNd1−xP4O12 waveguide laser layer epitaxially grown on LiNdP4O12 substrate

A LiBixNd1−xP4O12 laser waveguide was successfully fabricated on a LiNdP4O12 substrate by liquid‐phase epitaxy using LiPO3 as flux. cw laser oscillation at 1.05 μm was obtained with Ar ion laser coaxial pumping at room temperature.

High-pressure polymorph of silver pyrophosphate Ag4P2O7

Single crystals of a new polymorph of silver pyrophosphate, Ag4P2O7, were synthesized under high temperature and pressure conditions in the range of 400–550°C, 1.0–3.0GPa. Lattice parameters of the new phase are a=10.88, b=18.39, c=13.96A with space group C2221D52 (orthorhombic). The cell volume is contracted by a factor of 3.2% against the normal phase. The results of differential thermal analysis also proved the existence of a high-pressure polymorph.