New Nanostructured Fluorocompounds as UV Absorbers - Functionalized Inorganic Fluorides - page 233

12 C/min, annealing at 90 C for 30 min, and cooling down to room temperature. It should
be noted that for synthesis temperatures higher than 90 C, and annealing durations longer
than 30 min, TiO 2 anatase-type structure was obtained as impurity. At the end of the first
step, a limpid solution was obtained. The second step consisted in a microwave-assisted
precipitation under drying conditions (with an argon flow and a primary vacuum at 90 C);
the resulting white powder was recovered, further washed with alcohol and filtrated using
a Millipore Amicon Stirred Ultrafiltration Cell. Finally, the powder was outgassed at
100 C under primary vacuum for four hours.
8.3 Chemical Compositions and Structural Features of Ce and Ti-based
Oxyfluorides
8.3.1 Elemental Analysis
The Ce/Ca atomic ratio in the Ce-Ca based oxides and oxyfluorides as well as Ce-M-Na
based oxides and oxyfluorides with M ¼ Sn or Zr were determined by wavelength
dispersive spectrometry (WDS) using CAMECA SX 630 microprobe. The fluorine content
was quantified by F titration with a specific electrode. The F/Ti atomic ratio, as well as
the homogeneity of the sample, were checked by wavelength dispersive spectrometry
(WDS) using a CAMECA SX100 electron probe microanalysis (EPMA) on samples
pelletized to get a planar surface. The quantitative determination was performed on the
basis of the intensity measurements of the more energetic Ti, O, F X-ray emission lines
using TiO 2 and TiF 3 as reference compounds. Density measurements were performed
using either a liquid medium (bromobenzene) or Micromeritics pycnometer operating
under helium flow (Micromeritics AccuPyc 1330 Instrument).
Electronic Spin Resonance (ESR) spectra were recorded at T ¼ 5 K and at room
temperature on an ESR 500 Br¨ cker spectrophotometer working at ¼ 9.449 GHz in
order to identify the local environments of Ti 3 þ .
Thermal analyses were conducted in the temperature range 25-800 C using two
instruments: (i) a Setaram SETSYS Evolution thermoanalyser and (ii) a simultaneously
coupled TGA-MS device, a Netzsch STA 409C Skimmer , equipped with a Balzers QMG
421 and a Pulse TA unit. 25, 29, 45
8.3.2 Magnetic Measurements
In order to reach a conclusion about the absence of Ce 3 þ (4f 1 ) paramagnetic ions, the molar
magnetic susceptibility of some Ce-Ca-M (M ¼ Sn or Zr) and Ce-Sn-Na oxides and
oxyfluorides compounds were determined from the measurements of the magnetization
M(w ¼ M/H) at 300 K with a field of 4 T using the superconducting quantum interference
device (SQUID) magnetometer. The magnetization M (M ¼ w*H) was determined on
130-150 mg powdered sample in the temperature range 4-300 K with an applied field
(H) of 4 T.