Thelma J. Isaacs

Acousto‐optic properties of some chalcogenide crystals

We report results of extensive measurements on the acousto‐optic properties of several sulfosalt‐type chalcogenide crystals. These materials typically are transparent from the near ir to the intermediate ir, with refractive indices ranging from 2.5 to 3. Their acoustic velocities are among the lowest of any material, and ultrasonic attenuation remains low for frequencies to 500 MHz. These properties lead to exceptionally high acousto‐optic figures of merit.

Crystal growth and properties of TI3BX4 crystals for acoustic surface-wave and bulk acoustic devices

Crystals of Tl3TaS4 and T13Tase4 possess properties which indicate that they could be extremely useful for acoustic devices. They are piezoelectric, have low acoustic velocities (6.89 to 8.53 x 104 cm/sec), high effective values of electromagnetic coupling (k2 up to ~ 3%) and contain directions in which the thermal coefficients of delay are zero. Materials preparation and crystal growth and properties are described.

Tl3VS4 as an acousto-optic and surface wave material

Single crystals of thallium vanadium sulphide (Tl3VS4) up to 2 cm in length were grown from melts using the Stockbarger technique. This material has acoustic velocities as low as 8.73 × 104 cm/sec for bulk shear waves and 8.7 × 104 cm/sec for surface (Rayleigh) waves. In a sample oriented (001)Λ(110), k2 was found to be 1.39%, and the temperature coefficient of delay −54 ppm for surface waves. The optical transmission is from 0.75 to 10.5 µm, and the indices of refraction range from 3.156 at 0.749 µm to 2.808 at 5.26 µm. These properties make it an attractive candidate for use in acousto-optic and acoustic surface-wave devices.

Study of NaLaS2 as an infrared window material

Powders of NaLaS2 were synthesized and hot pressed into translucent discs about 95% dense whose hardness was 274 kg/mm2 (Knoop). The transmission range of the compound is from approximately 0.45-20 μm. Though optically clear discs could not be produced with our equipment, the trend of our data indicates that increasing pressure promotes increased density and transparency. The cubic symmetry of NaLaS2 was confirmed; a LiFeO2-type structure is proposed.

Titanium substitutions in andradites

Abstract Titanium-bearing andradites were studied by electron probe microanalysis and wet chemical analysis to determine the relation of titanium with iron and silicon, and the valence state of the titanium. Titanium is in the trivalent state and replaces iron in these minerals.

Structure of amorphous bulk As2 S5

Amorphous arsenic pentasulfide has been prepared and its structure characterized. Thin films have been prepared from bulk samples of the material by evaporation onto glass microscope slides and will be reported on in a later paper. X-ray diffraction techniques were used to investigate the structure of both the bulk and thin film samples. These data were analyzed using Warrens exact or direct method for analysis of X-ray scattering by two or more atoms in an amorphous material. Our study of bulk amorphous AS2S5 indicates a structure that agrees well with that determined by Diemann [1]; that is the arsenic is in four-fold coordination and the sulfur in six. The As-As bond is 1.77å and the S-S bond is 3.32å. The S-As-S bond angle is appro ximately 95°; the As-S-As angle is approximately 25°; and the base of the S-S-S tetrahedron is 60°. The short range order is similar to that of amorphous AS2S3, but the structure of AS2S5 is more rigid.

On the preparation and properties of some nonoxide chalcogenide glasses

Abstract Six nonoxide chalcogenide glasses were made and studied for optical transmission in the range 0.6–20 μm. Four of these materials, AgAsS 2 , TlAsSe 2 , TlAsSe 3 and Hg 3 Tl 4 As 8 Sb 2 S 20 , appeared to have useful transmission within this range, but absorption bands were seen which were ascribed to oxide impurities. The other two materials, AgTlS and TlAsS 2 , were opaque in the thicknesses of several millimeters used in the study.