Molybdate Single Crystals Research Articles

Pseudo-dendritic growth in lead molybdate single crystal by Czochralski technique

A pseudo-dendritic crystal growth of lead molybdate (PbMoO 4) has been studied with the Czochralski technique. The observed dendritic growth is iso-directional, projecting from the circumference of the growth front, where the content of impurities, melt stoichiometry and temperature are expected to be varied. The dendrite arm length and inter-dendrite angle are closely correlated. It is found that the grown dendrite arms are bounded only by ten low-index crystallographic planes (001), (00 1 ), (101), ( 1 01), (10 1 ), ( 1 0 1 ), (011), (0 1 1), (01 1 ), and (0 1 1 ). Based on this work, a facet transition pattern existing among the dendritic arms has been revealed. Further analysis for crystal grains in as-grown PbMoO 4 single crystals indicates that a similar dendritic growth can also occur under conventional growth conditions. It is further suggested that the constitutional supercooling is a major factor causing the dendritic growth in PbMoO 4 single crystals.

Pyroelectric properties and domain structure realignment in gadolinium molybdate single crystals

Abstract The combined effect of uniaxial mechanical compression and gradient heating on the pyroelectric properties and domain structure realignment processes in gadolinium molybdate single crystals has been studied. It is shown that the application of mechanical stresses under the condition of gradient heating results in a stabilization of the polarized state and in a shift of the phase transition point towards higher temperatures.

Raman spectra of lead molybdate single crystals

Abstract The first order Raman spectra and their temperature dependence of lead molybdate single crystals(PbMoO4) have been measured using Argon ion laser(= 5145A) as exciting radiation source. We obtained 13 Raman active modes which are in good agreement with the results of group theory, but 170 cm−1 mode of Ag is found at Ag + Bg scattering geometry at room temperature. Intensities of Ag, Bg and Eg modes decrease rapidly as temperature increases; Ag modes and Bg and Eg modes disappeared at 700 °C and 600 °C respectively but we did not find the soft mode related to any phase transition.

Spectral and lasing characteristics of CaMoO4:Nd3+single crystals

An investigation was made of a calcium molybdate single crystal activated with neodymium and a considerable anisotropy was found in its spectral and lasing properties. In the pulse-periodic regime an active element 4 mm in diameter and 55 mm long receiving a pump energy of 22.5 J at a repetition frequency of 50 Hz yielded an output power of 12 W at the wavelength of the ordinary wave λO = 1.061 μm.

Flash X-ray studies of the kinematics of domain switching in gadolinium molybdate single crystals

The kinematics of domain switching in gadolinium molybdate were used to test the feasibility of studying fast structural changes in crystalline solids by flash X-ray diffraction techniques. Our experiments show the feasibility of detecting the domain switching by flash X-ray diffraction and also indicate the possibility of a quantitative follow-up of the development of the switching process. The switching-time dependence upon the applied electrical field is in good agreement with data reported in the literature, thus proving the reliability of studying these phenomena by flash X-ray diffraction.

Laser Raman and far-infrared spectra of Gd 2(MoO 4) 3, Tb 2(MoO 4) 3, GdTb(MoO 4) 3, GdDY(MoO 4) 3, Tb 1.8Eu 0.2(MoO 4) 3 and Gd 0.2Dy 0.9Tb 0.9(MoO 4) 3 single crystals in the external mode region

Laser Raman and Fourier transform far-infrared (FT-FIR) spectra of rare earth molybdate single crystals of Gd 2(MoO 4) 3, Tb 2(MoO 4) 3, GdTb(MoO 4) 3, GdDy(MoO 4) 3, Tb 1.8Eu 0.2(MoO 4) 3 and Gd 0.2Dy 0.9Tb 0.9(MoO 4) 3 were recorded. Based on C 2ν symmetry, group theoretical analysis was carried out and a vibrational assignment is proposed for the lattice modes of the rare earth and molybdate ions. For the first time bands are observed in the region 10–40 cm −1 in FT-FIR spectra and they are assigned as difference bands. LO-TO splittings in these noncentrosymmetric systems are also discussed.

Electrical Conductivity of BaMoO4 Single Crystals

AbstractElectrical conductivity measurements have been made on the flux grown barium molybdate single crystals in the temperature range 425 to 1000 K. The mechanisms of conduction in the region of lower and higher temperatures have been distinguished.

The characterization of films deposited by chemical reaction on ferroelectric-ferroelastic gadolinium molybdate surfaces

X-ray diffraction, ion beam spectrochemical analysis, Auger electron spectroscopy and ion surface scattering techniques were used to characterize the chemically reacted film of gadolinium fluoride on the c surfaces of ferroelectric-ferroelastic gadolinium molybdate single crystals. Composition cersus depth profiles were obtained to determine the nature of the film and film-substrate interface. The ion beam spectrochemical analysis profile of hydrogen suggested a diffusion-controlled mechanism of film growth.

Brillouin scattering in the orthorhombic and tetragonal phases of gadolinium molybdate

Brillouin spectra in gadolinium molybdate single crystals have been investigated at 20°C and 200°C with a three-pass Fabry-Pérot interferometer. The elasticity tensor is deduced for both orthorhombic and tetragonal phases. The results are discussed in comparison with previous ultrasonic measurements.

Site occupancy of copper and gadolinium in PbMoO4 single crystals

Optical and electron-spin resonance measurements, at 78 and 300 °K, of copper-doped lead molybdate (PbMoO4) single crystals, with and without gadolinium trace impurity, have shown that: (i) Gd3+ occupies the Pb2+ substitutional site, (ii) copper enters the lattice as both Cu2+ and Cu+ in Gd-free crystals but mostly as Cu+ in Gd-doped crystals, and (iii) Cu2+ occupies several distinct sites, none of which has the S4 symmetry of the sites of either Pb2+ or Mo6+.

The preparation of cupric molybdate single crystals

The preparation of cupric molybdate single crystals