High Li content in a copper phosphatoantimonate with a novel layer structure: Li 5 CuSb(PO 4 ) 4

Abstract We present here the syntheses, crystal structure, and characterizations of a new mixed metal phosphatoantimonate, with the name of Li 5 CuSb(PO 4 ) 4 (LCSP), which was synthesized by traditional solid-state method for the first time. According to the single-crystal structure analysis, the title compound crystallizes in the triclinic system with space group P 1 ‾ $P\overline{1}$ , which features a novel 2D frameworks formed by the corner sharing PO 4 groups, SbO 6 octahedra, and CuO 4 pseudo plane tetrahedra. The anionic [CuSb(PO 4 ) 4 ] 5− cupro-stibio-phosphate layer is composed of two alternate chains of [Cu(PO 4 ) 2 ] 4− and [Sb(PO 4 ) 2 ] − further connected via the linkages of P–O–Sb. Characterizations including thermal and optical analyses have also been performed. The most impressive thing about the title compound is its layer structure and high Li content in its formula. AC impedance measurements have been carried out to study its conductivity. The representative impedance spectra of 250 °C, 300 °C and 350 °C indicated well-separated bulk arch and grain boundary arc in frequency domain. Linear fitting of arrhenius plot of bulk and GB conductivity showed that bulk activation energy was 1.00 ± 0.02 eV while GB activation energy was 1.30 ± 0.04 eV.