J.P. Chaminade

Crystal growth and characterization of InBO3:Tb3+

The growth of InBO3: Tb3+ single crystals has been investigated in connection with a feasibility study of low energy neutrino detectors. InBO3: Tb3+ crystals have been grown by slow cooling of high temperature solution using LiBO2 as a solvent. X-ray diffraction, optical studies, chemical etching and chemical analysis were carried out on the single crystals obtained. The luminescence properties of InBO3: Tb3+ single crystals have been recorded.

Fluoride crystals and high lying excited states of rare earth ions

Abstract We present the advantage of fluoride crystal hosts for the study of high lying localised excited states of rare earth ions. Special attention is devoted to the study of broad band UV emissions for solid state tuneable UV lasers and to the illustration of photoionisation mechanisms involving indium ions.

Ferroelastic properties of AlF3

Abstract A phase transition has been detected in AlF 3 at T C = 725 ± 10 K by calorimetric, X-ray diffraction and optical measurements. The structural relation between the low and high temperature phases has allowed to predict this transition to be a ferroelastic-prototype one. The observation of ferroelastic domains under polarizing microscope and their disappearance above Curie temperature are in good agreement with this assumption. The thermal dependence of the spontaneous strain has been determined.

Crystal structure and luminescent properties of indium titanate

The crystal structure of indium titanate (In[sub 2]TiO[sub 5]) has been refined from X-ray powder diffraction data by Rietveld refinement. In[sub 2]TiO[sub 5] is isostructural with In[sub 2]VO[sub 5]. It crystallizes in the orthorhombic space group Pnma with a = 7.2418(7) [angstrom], b = 3.5018(3) [angstrom], c = 14.890(2) [angstrom], V = 377.6(4) [angstrom][sup 3] and Z = 4. The final reliability factors were R[sub p] = 8.5%, R[sub wp] = 11.1% and R[sub I] = 5.6%. In[sub 2]TiO[sub 5] shows luminescent properties below 220 K. The luminescence is discussed in terms of crystal structure and compared to that of some other luminescent titanates and indates.

Electrical properties of pure In2O3 and Sn-doped In2O3 single crystals and ceramics

The transport properties of undoped and Sn-doped In2O3 (ITO) single crystals prepared by a flux method are reported. Hall measurements are detailed: they show that the mobility increases as the Sn dopant concentration increases. A maximum value of 100 cm2V−1s−1 is measured with an electron concentration of about 1.6 × 1020 cm−3. However, at high dopant concentration the mobility decreases again and the presence of neutral entities such as (SnO)x is expected to be responsible for this behavior. Some results dealing with undoped and Sn- or Pb-doped In2O3 ceramics are also presented and discussed.

A new strontium lithium titanium oxide, SrLi2Ti6O14: Crystal growth and structure determination

A new strontium lithium titanate with composition SrLi2Ti6O14 has been discovered in the ternary system SrO - Li2O - TiO2. Single crystals of this compound have been grown by the flux method. The structure of SrLi2Ti6O14 has been solved using X-ray data (Mo-Kα radiation, orthorhombic, space group Cmca, Z = 8, with a = 16.570(5), b = 11.150(2), c = 11.458(2) Å , R1 = 0.039 (wR2 = 0.087)). The crystal structure is built by edge and corner sharing TiO6 octahedra which form layers parallel to the (100) plane. Consecutive layers [deduced from a mirror plane parallel to (100)] are linked by common corners in the a direction. Lithium atoms in tetrahedral coordination occupy vacancies of the framework of titanium octahedra, while strontium atoms lie in 11-coordinated sites between two successive layers.

Preparation and structural characterization of two new titanium phosphates NaCa0.5Ti(PO4)3 and Ni0.5TiOPO4

Summary The titanium phosphate Na 4 Ca 0.5 Ti(PO 4 ) 3 crystallizes in the trigonal space group R32 (a h = 9.008 ± 0.002 A, c h = 21.814 ± 0.003 A and Z = 6). Its structure belongs to the nasicon type family. The titanyl phosphate Ni 0.5 TiOPO 4 crystallizes in a monoclinic unit cell, P2 I ,/c, (a = 7.383 ± 0.001 A, b = 7.323 ± 0.001 A, c = 7.344 ± 0.001 A, β = 120.23 ± 0.01° and Z = 4). The structure of these two compounds is based on a three-dimensional framework built of TiO 6 octahedra and PO 4 tetrahedra. The PO 4 tetrahedra are isolated in both Na 4 Ca 0.5 Ti(PO 4 ) 3 and Ni 0.5 TiOPO 4 . The TiO 6 octahedra are isolated in the former and linked together by “titanyl” oxygen atoms to form -Ti-O-Ti-O- infinite chains in the latter. These structural data are confirmed by the Raman spectroscopy study.

Crystal-field effect in CsCdBr3:Pr3+

Abstract Absorption as well as fluorescence measurements on CsCdBr 3 :Pr 3+ permit us to construct an energy level scheme for the main site occupied by the rare earth corresponding to the [RE 3+ -Vacancy-RE 3+ ] pair entity. A simulation of these levels made on the basis of a C 3v symmetry for the point site gives a low r.m.s. deviation. The crystal field parameters (CFPs) vary smoothly when compared with other rare earths embedded in the same matrix.

Flux growth of NdOCl single crystals

Abstract Neodymium oxide chloride single crystals up to 10 x 10 x 0.1 mm3 have been grown from molten neodymium chloride in the temperature range 900-700°C. A slow-cooling technique (3°C/h) with a sealed platinum-10% rhodium crucible was used. The best crystals are transparent, pale purple in color and have well developed (001) faces. They have been characterized by X-ray diffraction and optical measurements.

The crystal structure of eulytite Na3Bi5(PO4)6

Abstract The crystal structure of Na 3 Bi 5 (PO 4 ) 6 was solved using the single-crystal X-ray diffraction technique. The structural refinement has led to a reliability factor of R 1 =0.0257 ( wR 2 =0.0533) for 428 independent reflections. This compound was found to crystallize in the cubic system (space group I 43 d ) with eulytite structure and the lattice parameters: a =10.097 (4) A, V =1029.38 A 3 , Z =2, D calc. =5.43 g cm −3 ( D exp. =5.32(5) g cm −3 ). The structure is characterized by the existence of one single general position (48a) for oxygen anions and two distinguished positions (16c) occupied by Na + and Bi 3+ cations, respectively. The site occupation factors are equal to 3/8 and 5/8 for sodium and bismuth, respectively. Although all Pue5f8O distances are identical (1.529(4) A), the Oue5f8Pue5f8O angles ranging from 108.06 (15) to 112.32 (31)°, show that [PO 4 ] 3− are rather distorted. Both sodium and bismuth cations are located in octahedral sites with corresponding mean distances of Naue5f8O and Biue5f8O equal to 2.428 and 2.386 A, respectively. As expected from the close values of the ionic radii of Na + and Bi 3+ , these distances lie in the same range.