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Cubic, disordered α-LiFeO2 has been prepared as a polycrystalline powder by two methods, and in the form of single crystals grown from a ternary melt. It was found impossible to induce phase-transformations in one type of polycrystalline sample, and this has been attributed to a deficiency of iron ions in its composition. Phase transformations in the other samples have been studied by means of a high-temperature X-ray powder diffraction camera. By using the results from powder diffraction together with data from Weissenberg single crystal photographs, a new sequence is proposed for the transformations. differing from that reported by Collongues and by Fayard. The α-phase, which is unstable, transforms to a body-centred tetragonal β-phase belonging to the point group I 4/m, and differs from the AuCu structure proposed by previous authors. The β-phase transforms to an ordered γ-phase which, in turn, disorders to form the α-phase.

Composition diagrams showing approximate boundaries in which various crystals can be grown were determined in several systems for several heating temperatures. These systems include Mo O 3 Ga 2 O 3 Sm 2 O 3 , PbO/PbF 2 Ga 2 O 3 Sm 3 , PbO/Pb F 2 Fe 2 O 3 Sm 2 O 3 , B 2 O 3 Fe 2 O 3 Li 2 O and Mo O 3 Gd 2 O 3 Na 2 O.

The magnetic moments of the single-crystal garnets ${\mathrm{Yb}}_{2.9\ensuremath{-}x}{\mathrm{Bi}}_{0.1}{\mathrm{Ca}}_{x}{\mathrm{Fe}}_{5\ensuremath{-}x}{\mathrm{Si}}_{x}{\mathrm{O}}_{12}$, with $0lx\ensuremath{\le}1.4$, have been determined between 4.2 and 295\ifmmode^\circ\else\textdegree\fi{}K, in magnetic fields up to 15 kOe. Using the molecular-field model and assuming a random distribution of the substituted ions with a random distribution of canting angles, the temperature dependence of the spontaneous magnetization of the Si-Ca-substituted ytterbium iron garnet (YbIG) was explained. A theoretical fit to the experimental results was obtained using the exchange parameters of pure YbIG, assuming they are the same for the substituted crystals.

The kinetics of crystal growth of ferroelectric Rochelle salt have been studied by applying an electric field of 2–1000 V/cm between the upper face of a crystal and an electrode immersed in the water solution in contact with the lower part of the growing or dissolving crystal. It has been found that the rate of growth decreases while the rate of dissolution increases by about 10% above and below Tc of 24°C of the crystal at 900 V/cm. The results are discussed theoretically. Similar experiments under the application of a uniaxial pressure showed a less significant effect, while a vibrating alternating pressure of about 8 kg/cm2, and 50 cycles/sec showed a significant increase of the rate of growth by about 50%.

Single crystals with the compositions (A) = Yb 3 Fe 5 − x Ga x O 12 with x varying from 0.5 to 4.0 and (B) = Y 2.9 − x Bi 0.1 Ca x Fe 5 − x- Si x O 12 with x varying from 0.6 to 1.3 have been grown from flux. Crystals of compositions (A) are crystallized from a PbO/PbF 2 solvent, whereas crystals of compositions (B) are from a PbO/B 2 O 3 solvent. The unit-cell dimensions, the ferrimagnetic Curie temperature and the segregation coefficients of Ga 3+ in (A) and Ca 2+ in (B) have been determined. The difference between the two fluxes is discussed.

Thin films of silicon have been deposited epitaxially by chemical vapor deposition using tetramethyl silane, Si(CH 3 ) 4 , (TMS) as the transporting agent. Silicon carbide has been found in varying amounts as a contaminating agent depending upon temperature of deposition and presence of hydrogen during the etching or reaction. Experiments below 1100°C formed amorphous silicon films containing large amounts of SiC as revealed by the wide infrared absorption band around 790 cm -1 characteristic of cubic SiC.

The magnetic properties of R M 2− x Si x and R M 2− x Ge x where R = La, Ce, Nd, Sm, Eu and Gd and M = Fe, Co, Ni and Ag have been measured. It has been found that for samples of x = 0.4 both R and M sublattices are paramagnetically above 4.2δ K in the high spin state, whereas, if x = 0.67, R is magnetically ordered whereas M is diamagnetic.

Magnetic susceptibilities of R Mn2O5 where R=Sm, Tb, Ho, and Lu have been measured between 1.4 and 300°K in magnetic fields up to 15.3 kOe. A high magnetic anisotropy has been found in TbMn2O5 and HoMn2O5. The anisotropy of TbMn2O5 was explained in terms of two closely spaced singlets of the ground state of Tb3+.

The reduction in hydrogen and water vapor of α-Fe 2 O 3 was studied between 200° and 450°C. For equal partial pressures of water and hydrogen, a phase of γ-Fe 2 O 3 in the Fe 3 O 4 can be identified already at 250°C. When the relative amount of water vapor is reduced, the γ-Fe 2 O 3 is seen only in higher temperatures, starting at 350°C when the hydrogen is practically dry. At 400°C, regardless of the water amount present, α-Fe 2 O 3 is fully transformed into Fe 3 O 4 ? still higher temperatures, further reduction takes place to FeO and to metallic iron. The ? of γ-Fe 2 O 3 (in the temperature range where it was formed) mixed with magnetite was ? chemical determination of Fe 2+ , by magnetic measurements and by Mossbauer effect ? When samples of Fe 3 O 4 prepared by reducing α-Fe 2 O 3 at 400°C, w? , pure γ-Fe 2 O 3 phase was obtained. Hydrogen was found to be released from γ-Fe 2 O 3 when heated. About 7? necessary hydrogen amount to give the formula H 1 2 Fe 5 2 O 4 suggested by Br? . This shows that γ-Fe 2 O 3 does actually, at least in part, consist of this spinelli ? . That it is only partly so was suggested by Braun in view of the magnetic ? so seeems to be suggested by our study of the transitions from γ- to α-Fe 2 O 3 in He and O ? ospheres, respectively, which indicate that the γ-Fe 2 O 3 is composed of two different phases.

The rate of hydrothermal growth R of quartz in a 1 M solution of NaOH without and with additions of V+5, Ga+3, Mg+2, Zn+2 and Ge+4 impurities in the proportions of 0.01 to 0.5 M in the growth solution has been measured. R increases with a decrease in the concentration of added impurity and is always smaller compared to the rate in the pure solutions except for quartz grown in the presence of low concentrations of Mg+2. Electron microprobe analysis of the doped quartz with Ga and Zn grown at a ΔT#62;20 °C show the presence of disk shaped defects of about 2 microns diameter containing segregations of Ga+3 or Zn+2 accompanied by Fe+3. The concentration of the Ga+3 or Zn+2 in the defect is of the order of 103–104 ppm as compared to about 10–102 ppm for its concentration in the matrix. The concentration of Fe+3 in the defect is of the order of 104–105 ppm compared to 10–102 ppm in the matrix. Doping with V+5 does not produce segregation at defects.

The detection of the photopeak of the 662‐keV γ ray of 137Cs with a full width at half‐maximum (FWHM) of only 6.5 keV by a 0.5‐mm‐thick improved stoichiometry HgI2 crystal is reported. The 1173‐ and 1332‐keV γ photopeaks of 60Co have also been resolved for the first time. Polarization effects were negligible.

Mercuric iodide is a wide bandgap semiconductor, with Eg approx. = 2.14 eV at room temperature. Therefore, HgI/sub 2/ is totally different from the well-studied, narrower gap, elemental semiconductors such as Si and Ge, and also different in its physical and chemical properties from the known semiconductor binary zinc-blend compounds such as GaAs or InP. The purpose of studies in the last decade was to further our understanding of HgI/sub 2/; recent progress is reported. (WHK)

Large single crystals of CdSe weighing about 30g were grown by the vertical unseeded vapor growth technique at a linear growth rate of 5mm/day and a temperature gradient of 10°C/cm. Crystal perfection and homogeneity were evaluated by Laue X-ray diffraction, etch pit density, SEM and microprobe analysis methods. The dark resistivity of the as-grown and the heat treated crystal was about 1?cm and 1012?cm respectively. Slices were used to fabricate room temperature detectors for nuclear radiation energy. The detectors showed high efficiency and stability as a function of time for radiation sources from 1OKeV to 66OKeV.

A novel ternary semiconductor compound Cd0.7Zn0.3Se has been developed as a nuclear radiation detector. A higher energy band gap comparatively to the binary CdSe enabled the preparation of detectors with a lower leakage current and consequently a lower electronic noise. As a result lower noise threshold could be obtained allowing nuclear spectrometry down to the energy of 6KeV. The charge collection efficiency has been studied as a function of voltage applied to a thin Cd0.7Zn0.3Se platelet. The limitation of transport properties is discussed in terms of bulk trapping versus surface recombination of charge carriers.

The use of HgI2 as a thermal‐neutron solid‐state electronic detector, in particular its application for neutron diffractometry, is demonstrated for the first time. A single crystal HgI2 detector is used to count prompt gamma emissions (0.2–5 MeV) from (n,γ) nuclear reactions in Gd or Cd foils. The neutron counting efficiency depends on the HgI2 detector thickness. For a 1‐mm thickness of HgI2 the efficiency is about 10% compared to the efficiency of a 10BF3 gas detector.

Single crystals of R2.9−xBi0.1CaxFe5−xSixO12 where R = Y or Yb and 0.6 < x < 1.5 have been grown from a PbOB2O3 flux. The crystals have been characterized by measurements of the unit cell dimension, Curie temperature and magnetization measurements between liquid helium and room temperature.

Sm atoms in SmFe 0.67 Ge 1.33 are antiferromagnetically ordered with T N = 26° K , and with a Curie constant of 0.0737. Comparison with the Curie constant 0.082 of the free ion Sm 3+ , indicates that the Fe atoms do not contribute to the magnetic moment of the compound. The isomorphic GdFe(Co) 0.4 Si 1.6 compounds are paramagnetic above 4.2°K. The Fe and Co atoms are in a high spin state yielding Curie constants of 10.18 and 9.99 for the Fe and Co compounds respectively.

The differential thermal analysis (DTA) technique is used to measure the Curie temperature of yttrium iron garnets, and of the garnets obtained by partially substituting Sm, Nd, Pr, or La for the Y. The accuracy of the method is within about 1°C. It is found that in all the above substitutions the Curie point is increased more or less linearily in the rare‐earth contents, with the largest slope for Pr, somewhat less for Nd and Sm. For La, only the compound Y2.5La0.5Fe5O12 could be prepared and it did not show any measurable change from the Curie point of pure yttrium iron garnet. Two possible explanation are suggested to the increase in Curie point by Sm substitution, which does not change the magnetization of the garnet.

The composition ${\mathrm{La}}^{3+}$${\mathrm{Fe}}^{2+}$${\mathrm{Fe}}_{11}^{3+}$${\mathrm{O}}_{19}$ was prepared by sintering the oxides, and its magnetic moment was measured from liquid air temperature to the Curie point. At the lowest temperature a value of 17.5 Bohr magnetons per formula weight was obtained, as compared with 19 Bohr magnetons of Ba${\mathrm{Fe}}_{12}^{3+}$${\mathrm{O}}_{19}$. The difference is qualitatively understood if the ${\mathrm{Fe}}^{2+}$ ion is a nearest neighbor to the ${\mathrm{La}}^{3+}$ in the crystal, i.e., in the [$12K$] site, thus decreasing the total magnetic moment. The Curie temperature is 695\ifmmode^\circ\else\textdegree\fi{}K, compared to 725\ifmmode^\circ\else\textdegree\fi{}K of Ba${\mathrm{Fe}}_{12}^{3+}$${\mathrm{O}}_{19}$. The lower Curie point can again be qualitatively explained by less exchange interaction with the divalent iron of La${\mathrm{Fe}}^{2+}$${\mathrm{Fe}}_{11}^{3+}$${\mathrm{O}}_{19}$, or possibly by the change in unit cell dimension which modifies the short-range exchange interaction between the iron ions.

The preparation and saturation magnetization of yttrium‐iron garnets containing various amounts of neodymium was investigated. The amount of Nd which can be incorporated in the garnet structure was determined crystallographically and magnetically. The chemical analysis of the Nd/Y ratio was carried out by the counting of the characteristic x rays of Nd produced by proton bombardment in a Van de Graaff accelerator. A compound with a formula of YNd2Fe5O12 was found to be the richest iron garnet containing Nd and has a saturation magnetization, at room temperature, of 4.25±0.13 Bohr magnetons per formula weight compared to that of 3.55±0.13 of Y3Fe5O12 or Sm3Fe5O12.

Thin films of Ge produced by the pyrolysis of alkyl germanium tetramethyl germanium and tetraethyl germanium compounds have been studied for their rates of deposition, crystallinity, and carbon contamination. The pyrolysis reaction has been found to be of first order, and the activation energies have been found to vary with concentration of the alkyl germanium compound between the limits of 25–30 kcal/mole for both tetramethyl and tetraethyl germanium. The morphology and crystallinity of the films vary with the chemical and crystalline structure of the substrate. Good quality and uniform films are produced on monocrystalline germanium substrates preetched in situ with gas. The carbon contamination is found to be strongly dependent on the substrate material, and it varies between 25 ppm for germanium and 200–50,000 ppm for tungsten substrates.

Es wird uber eine neue Abscheidungsmethode von SiO2- Filmen aus der Dampfphase′ durch Oxidation von dampfformigen Alkylsilanen berichtet.

Gamma rays from 137Cs have been resolved using room‐temperature HgI2 detectors in three different configurations. The methods used were (i) single charge collection in a thick quasihemispherical‐shaped detector (ii) a thin HgI2 detector irradiated edge‐on, and (iii) pulse rise‐time discrimination with a thin detector irradiated face‐on.

Low-resolution and therefore low-cost mercuric iodide detectors have successfully been applied to replace the combination of a graphite monochromator and a proportional gas radiation counter used in X-ray diffractometers. The mercuric iodide detector requires a lower DC bias of only 200 V rather than the 1500 V bias needed for the proportional gas counter. The much better stopping power of HgI2 allows higher counting efficiency and therefore a better signal-to-noise ratio. Results are shown for X-ray powder diffractions of polycrystalline cubic silicon and tetragonal HgI2.

Differential scanning calorimetry measurements of mercuric iodide (HgI2 ) do not suggest the existence of the α’‐HgI2 phase, as previously reported, when the necessary precautions are taken to avoid any chemical reaction with the sample holder. This conclusion is supported by variable temperature Raman spectroscopic measurements performed in the vicinity of the melting point, where the α’ was supposed to exist.

The magnetic susceptibilities of single crystalline and polycrystalline Eu3O4 and of polycrystalline EuGd2O4 in the range between 2° and 300°K are reported. The compounds are antiferromagnetic with TN=5.0° and 4.5°K, respectively. Above TN the susceptibilities follow Curie—Weiss laws, with θP=−5° and +2°K, respectively. Eu3O4 is metamagnetic below TN with Hc=2.4 kOe at 2°K. Possible magnetic structures for Eu3O4 are discussed.

Charge compensation by substituting univalent fluorine for divalent oxygen in spinel type ferrites was studied by preparing and analyzing single‐phase polycrystalline materials. Starting with a 1:1 molar ratio of divalent fluorides and Fe2O3, charge compensation was mainly achieved by metal vacancies, although some Fe2+ was also present. The preparative method, unit cell dimensions, chemical compositions, magnetic moments at 90°K and Curie points for these compounds are given. Their properties can be interpreted as those of solid solutions of mainly γ‐Fe2O3 and a stoichiometric fluorine ferrite M22+Fe3+O32−F−, where M is Mg, Mn, Co, Ni, or Zn.

The magnetic susceptibilities of the scheelites R1/2Na1/2MoO4, with R = Gd, Tb, Dy, Ho, Er, Tm, and Yb, have been measured between 2° and 300°K. The compounds are paramagnetic and show large, axial anisotropy at low temperatures. The wavefunctions and energy levels are deduced for the Yb compound and compared to values which have been obtained in CaWO4. The variations in magnetic anisotropy from ion to ion are correlated with the crystal field inferred for the Yb compound.

Magnetic moment measurements along the [10 1 0] direction in single crystal Tm at 4.2°K are presented for fields up to 140 kG. A value of σ of about 220 emu/gm, by far the highest reported for Tm, is obtained at 140 kG and is close to the value expected for Tm3+ (7μB). The data indicate that the saturation value of σ is even higher. Lack of single crystals and high fields as well as the high anisotropy energy of Tm all conspired to limit previous measurements and their interpretation.

Magnetic‐moment measurements are presented for single‐crystal Tm, Eu, Sm, and Yb along principal axes. The 4.2°K data for Tm and Eu extend to 140 kG, and the Sm and Yb results, at low field, range from 4.2° to ∼300°K. Almost complete ferromagnetic alignment in Tm is attained for 140 kG along the [1010] direction. A value of almost 7 μB is observed. Eu is antiferromagnetic, shows a linear variation of σ vs Bo up to 140 kG (in disagreement with earlier data), and appears to be isotropic. The susceptibility for Yb shows a small isotropic paramagnetic component, possibly caused by impurities. Single‐crystal data show that Sm is a uniaxial antiferromagnet with spins aligned along the c axis and TN=14°K.