Structural Study of Electrochemically Obtained Li2+xTi3O7

Single crystals of the high-pressure phase of (VO)2P2O7 were grown by slowly cooling the melt at 3 GPa. Relevant reactions at high pressure and high temperature were studied in advance by in situ X-ray diffraction (XRD) measurements. The crystal structure of the high-pressure phase was determined by single-crystal XRD. Magnetic susceptibility of the crystal was measured along the three principal axes and analyzed using a S= Heisenberg AF alternating-exchange chain model. A good fit was obtained using the g values determined by ESR measurements, J1/kB=131.6(1) K, and an alternation parameter of J2/J1=0.8709(5). The spin gap was estimated to be /kB=33.4(2) K.