Facile Synthesis, Characterization and Electrical Properties of Apatite-type Lanthanum Germanates
E. Rodríguez-Reyna; A.F. Fuentes; J. Hanuza; M. Maczka; K. Boulahya; U. Amador. Facile Synthesis, Characterization and Electrical Properties of Apatite-type Lanthanum Germanates. Solid State Sciences (ISSN: 1293-2558). 2006, Vol. 8, p. 168-2006.
Apatite-type lanthanum germanates La10−x(GeO4)6O3−1.5x , have been successfully prepared at room temperature in a planetary ball mill by dry milling for only 6 hours (rotating disc speed = 350 rpm), stoichiometric mixtures of hexagonal A–La2O3 and GeO2. As obtained powders are not amorphous and show XRD patterns as well as IR and Raman spectra characteristic of the apatite-type lanthanum germanates. The domain size of the as prepared samples grows gradually with the temperature of post-milling thermal treatment with an activation energy of about
20 kJ mol−1 K−1. The IR and Raman spectra suggest increasing ordering with firing temperature. The electrical properties of the as prepared materials, sintered at temperatures as low as 1200 ◦C, are similar to those found for the same phases but prepared by conventional solid state
reaction and sintered at higher temperatures (σdc = 4 × 10−3 Scm−1 at 650 ◦C and 3 × 10−2 Scm−1 at 950 ◦C). Two different regimes are identified in the Arrhenius plots with activation energies of around 1 eV (below 650 ◦C) and 0.6 eV (above 650 ◦C).
Apatite-type lanthanum germanates La10−x(GeO4)6O3−1.5x , have been successfully prepared at room temperature in a planetary ball mill by dry milling for only 6 hours (rotating disc speed = 350 rpm), stoichiometric mixtures of hexagonal A–La2O3 and GeO2. As obtained powders are not amorphous and show XRD patterns as well as IR and Raman spectra characteristic of the apatite-type lanthanum germanates. The domain size of the as prepared samples grows gradually with the temperature of post-milling thermal treatment with an activation energy of about
20 kJ mol−1 K−1. The IR and Raman spectra suggest increasing ordering with firing temperature. The electrical properties of the as prepared materials, sintered at temperatures as low as 1200 ◦C, are similar to those found for the same phases but prepared by conventional solid state
reaction and sintered at higher temperatures (σdc = 4 × 10−3 Scm−1 at 650 ◦C and 3 × 10−2 Scm−1 at 950 ◦C). Two different regimes are identified in the Arrhenius plots with activation energies of around 1 eV (below 650 ◦C) and 0.6 eV (above 650 ◦C).