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以五氧化二铌(Nb2O5)、一水氢氧化锂(LiOH·H2O)和钛酸四丁酯(Ti(C4H9O)4)为原料、柠檬酸为络合剂,通过调节pH值和温度,用溶胶-凝胶法(sol-gel)成功获得透明溶胶。经700℃煅烧,用化学法合成单相钛酸锂(Li2TiO3)固溶体相(Li2.06Nb0.18Ti0.76O3)粉体,其合成温度比普通固相法的低150℃左右。用红外光谱、X射线衍射及扫描电镜(scanning electron microscope,SEM)等表征柠檬酸盐前驱体及煅烧后粉体的性能,详细研究煅烧过程中晶相的转变过程,提出合理的转变机制。结果表明:在煅烧过程中,除Li2TiO3固溶体相外,还出现锐钛矿相TiO2和M相等中间相。随着温度进一步上升,这些中间相消失,最终在700℃得到纯Li2TiO3固溶体相。通过SEM可观察到结晶良好的棒状和块状Li2TiO3固溶体相粉体颗粒。分别研究采用sol-gel和固相法制备样品的烧结性能、显微结及介电性能,结果表明:采用sol-gel得到粉体制备的陶瓷具有特殊的大、小晶粒共存的两种Li2TiO3固溶体相的显微结构,在较低温度(825℃)即达到最大的体积密度3.456g/cm3。与固相法制备样品相比,sol-gel制备样品在同一频率的相对介电常数较小、介电损耗更低。
Using niobium pentoxide (Nb2O5), lithium hydroxide monohydrate (LiOH · H2O) and tetrabutyl titanate (Ti (C4H9O) 4) as raw materials and citric acid as the complexing agent, by adjusting pH value and temperature, Transparent sols were successfully obtained by sol-gel. After calcination at 700 ℃, a single phase lithium titanate (Li2TiO3) solid solution phase (Li2.06Nb0.18Ti0.76O3) powder was synthesized by chemical method. The synthesis temperature is about 150 ℃ lower than the ordinary solid phase method. The properties of citrate precursors and calcined powders were characterized by FTIR, X-ray diffraction and scanning electron microscopy (SEM). The transformation process of the crystalline phases during calcination was studied in detail and a reasonable transformation mechanism was proposed. The results show that in addition to Li2TiO3 solid solution phase, anatase phase TiO2 and M equivalent mesophase appear during calcination. As the temperature rises further, these mesophases disappear and finally a pure Li2TiO3 solid solution phase is obtained at 700C. Well-crystallized rod-like and bulk Li2TiO3 solid solution phase powder particles were observed by SEM. The sintering performance, microstructure and dielectric properties of the samples prepared by sol-gel and solid-state methods were studied respectively. The results showed that two kinds of Li2TiO3 ceramics with special large and small grains were obtained by sol- The microstructure of the solid solution phase reaches a maximum bulk density of 3.456 g / cm3 at a lower temperature (825 ° C). Compared with the samples prepared by the solid-phase method, the samples prepared by sol-gel have the smaller relative dielectric constant and the lower dielectric loss at the same frequency.