Crystal Structure and Ionic Conductivity in NASICON Compounds of MZr2(PO4)3 (M=Li Na K Cs)

Abstract

NASICON material is a promising solid-state electrolyte because of its distinctive crystal structure and high ionic conductivity The bottleneck size for the ionic channel of crystal structure affects Na+ ionic conductivity To discuss the relation between crystal structure and ionic conductivity we cited the data about MZr2(PO4)3 (M=Li Na K Cs) and Na1+xZr2SixP3-xO12 (0 < x < 3) from the ICSD database In this study we calculate the area of the bottleneck by the shape of a triangle and an inscribed circle The powder of NASICON compounds is prepared by solution-assisted solid-state reaction and identified by X-ray diffraction We adopted the Rietveld refinement approach and Diamond software to calculate the bottleneck size of the ion channel The XRD pattern showed that nearly a single phase could be obtained for NaZr2(PO4)3 Na2Zr2SiP2O12 Na3Zr2Si2PO12 KZr2(PO4)3 and partial solid-solution could be obtained for Na0 5K0 5Zr2(PO4)3 through calcined at two-stage 600℃/6 h-1000℃/12 h Adopting the same condition of calcination Na3-xKxZr2Si2PO12 (x=3 1 0 5 0 1 0 05) solid-solution would not be formed and have several phases Powders for NASICON compound was formed into a pellet with uniaxial compression NaZr2(PO4)3 Na0 5K0 5Zr2(PO4)3 KZr2(PO4)3 was sintered at 1200℃/10 h contains 2wt% MgO and Na2Zr2SiP2O12 Na3Zr2Si2PO12 at 1250℃/10 h to obtain a relative density > 90% The electrical conductivity of the ceramic body is measured with direct current analysis We found that the ionic conductivity in room temperature of MZr2(PO4) (M=Na Na0 5K0 5 K) is negatively related to the bottleneck size Higher K+ content broadens the bottleneck size but decreased the ionic conductivity The room temperature ionic conductivity of Na1+xZr2SixP3-xO12 (x=0 1 2) is positively related to the bottleneck size Higher Si4+ content broadens the bottleneck size and increased ionic conductivity

Date of Award	2020
Original language	English
Supervisor	Chi-Yuen Huang (Supervisor)