Order–Disorder and Mobility of Li+ in the β′- and β-LiZr2(PO4)3 Ionic Conductors: A Neutron Diffraction Study

✍ Scribed by M. Catti; N. Morgante; R.M. Ibberson

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 353 KB
• Volume: 152
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8658

✦ Synopsis

Neutron di4raction pro5les at high resolution (HRPD, ISIS Facility, U.K.) were collected on powder samples of LiZr2(PO4)3 at 203C ( phase, monoclinic P21/n, Z ‫؍‬ 4; a ‫؍‬ 8.81277(4), b ‫؍‬ 8.94520(5), c ‫؍‬ 12.37540(6) A s , ‫؍‬ 90.801(1)3) and at 3503C ( phase, orthorhombic Pbna, Z ‫؍‬ 4; a ‫؍‬ 8.84303( 5), b ‫؍‬ 8.94120(6 ), c ‫؍‬ 12.41301(8) A s ). All Li sites were located by di4erence Fourier maps in tetrahedral coordination, and both structures were Rietveld-re5ned to wRp ‫؍‬ 0.0353 ( ) and 0.0429 ( ). The structure is a distortion of , with a [100] pseudo-twofold axis x, 1/2؊ y, ؊ z relating all atoms but lithium, which is fully ordered (1Li+O2 ‫؍‬ 2.02 A s ). In the phase, Li is disordered over four sites, of which two (Li1 and Li2) are symmetry-independent with occupancies 0.34(1) and 0.16(1), respectively, and 1Li+O2 ‫؍‬ 2.17 and 2.16 A s . The disorder fully explains the higher Li ؉ mobility in the with respect to the phase observed from ionic conductivity data. Mechanisms of ion transport are proposed, and the relationship to the NASICONtype / phase of LiZr 2 (PO4)3 is analyzed in detail. 2000 Academic Press