在微波辐照下Li_(1+x)Mn_(2-x)O_4尖晶石的固相合成

Synthesis of spinel Li(1+x)Mn(2-x)O4 under microwave irradiation

采用微波直接加热方法在不同温度与氧分压条件下制备出Li_(1+x)Mn_(2-x)0_4(x=0、0.025、0.05、0.15)尖晶石氧化物。利用XRD与SEM/EDX等手段研究了合成样品的晶体结构、形貌特征以及相交特点。在850～1200℃氧气氛下加热时,合成的样品由立方尖晶石相和微量的杂相Li_2MnO_3组成,而且随着温度升高,晶体中阳离子混合现象减少,晶体结构的对称性增大,但是晶体结构的参数基本不变。Li_1+xMn_2-x0_4样品中杂相Li_2Mn0_3的含量随x的增大而增加。在相同的温度与氧分压下,用微波加热合成的尖晶石氧化物的热稳定性比用常规加热方法合成的高。用微波加热合成的尖晶石氧化物结晶度好,晶体颗粒呈规则的八面体或多面体形态。

Spinel-type Li1+xMn2-xO4 (x=0, 0.025, 0.05, 0.15) oxides were prepared by single microwave irradiation under the condition of various temperatures and oxygen partial pressures in the temperature range of 850-1200°C. XRD and SEM/EDX were used to characterize the crystal structure, morphology and phase transition processes of the as-synthesized samples. The samples heated in flowing oxygen and the microwave field consist of major cubic spinel and trace of Li2MnO3 impurity all the time. With the increase of temperature, the amount of cation-mixing in spinel structure decreased and symmetry of the crystal structure enhanced. In the whole temperature ranges, crystal structure of the spinel oxides did not change basically. The amount of the impurity phase Li2MnO3 increases with the increasing of x value. Under the same conditions of temperature and oxygen partial pressure, the thermal stability of spinel-type LiMn2O4 oxides prepared by microwave heating was better than those by conventional method. The particles of the spinel oxides prepared in microwave field have very regular octahedron or polyhedron crystal morphology with well crystallization.