Dimorphism, phase transitions, and transport properties in LiZr2(PO4)3

The authors report the structure, the phase transitions, and the transport properties of two different phases of LiZr{sub 2}(PO{sub 4}){sub 3} materials prepared by the sol/gel technique. The phase have been characterized by X-ray powder diffractometry, thermal analysis, ac conductivity, and NMR ({sup 31}P and {sup 7}Li). A high-temperature phase, prepared at 1,200{degree}C, shows a NASICON-type structure and a monoclinic {yields} rhombohedral first order transition at about 40{degree}C. This transformation is associated with the sharp appearance of a lithium motion leading to high conducting properties above the phase transition {sigma} = 1.2.10{sup {minus}2} ({Omega} cm){sup {minus}1} at 300{degree}C. A low-temperature phase, prepared at 900{degree}C, exhibits the {beta}-Fe{sub 2}(SO{sub 4}){sub 3}-type structure and a monoclinic {yields} orthorhombic transformation at 300{degree}C. A local lithium motion progressively takes place between RT and 120{degree}C and a conducting state is observed at 300{degree}C ({sigma} =5.10{sup {minus}4} ({Omega} cm){sup {minus}1}). In diphasic samples prepared between 900 and 1200{degree}C, both resistivity and activation energy progressively increase with the low-high temperature phase ratio.