Understanding The Microstructure Of Li_0.5Na_0.5CoO₂Syntheiszed By Solid-state Reaction Method

:LixNayCoO2(x≈0.5, y≈0.5), a functional ceramic material system, has drawn a lot of attention from researchers recently. In this thesis, Li0.5Na0.5CoO2was successfully synthesized by the solid-state reaction method. Various characterization methods were used to understand the crystal structure and morphology of the as-synthesized Li0.5Na0.5CoO2, including differential scanning calorimeter (DSC), and X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometercopy (ACP-AES), scanning electron microscopy (SEM), transmission electron microscopy (TEM). And the conclusions as following:1. A better synthesis process of NaCoO2which is sintering mixture of Na2O2and Co3O4at350℃and500℃respectively was found.2. Products of Li0.5Na0.5CoCO2power were obtained by using NaCoO2, Li2CO3and2CoCO3·3Co(OH)2·3H2O as the precursors, which were firstly intimately mixed and heated at750℃for8～12h in air, and then quenched in air. The product composed of Li0.5Na0.5CoO2, was found that it has a similar crystal structure with layered LiCoO2(R-3M) from XRD and the chemical stoichiometries of Li and Na are0.47and0.40respectively. The size of Li0.5Na0.5CoO2grains increases with the sintering time and the maximum grain can reach5μm.3. There are two different phases in Li0.5Na0.5CoO2power. One of them belongs to group space R-3m and Li and Na are all at3a site. The other one is primitive hexagonal crystal structure and its alkali atoms range as Li-Na-Li/Na-Li-Na-Li/Na.4. Products with P63/mmc Li0.5Na0.5CoO2phase whose lattice para meter are a=2.856A, c=20.3923A, were obtained by using Na CoO2and LiCo02as the precursors, which were mixed and hea ted at850℃in air for24h and then quenched in air. The che mical stoichiometries of Li and Na are0.43and0.40respectivel y and’floor-like’morphology at the edge of hcp-Li0.5Na0.5CoO2was found. 5. The electron diffraction patterns taken in TEM confirm the P63/mmc crystal structure of Li0.5Na0.5CoO2. Electron diffraction pat-t erns got along different zone axes of one grain and other electr-on diffraction patterns of different grains all match the structure.