Preparation Of One - Dimensional Barium Strontium Titanate Crystals By Hydrothermal Method And Its Growth Mechanism

The curie temperature, dielectric properties, optical properties as well as piezoelectric properties of the barium strontium titanate crystals can be adjusted by altering the proportion of the barium ion and the strontium ion. As the functional materials, the BST was popular in the small size and large capacity devicest, such as the unable microwave devices, phase shifters, infrared detection and dynamic random access memory, the morphology of crystal seriously affected the function of the material. The study of the one-dimensional crystal caused widespread concern because the function of one-dimensional direction of one-dimensional crystal could be much better than other planes.The amorphous gel and the gel containing anatase TiO2crystalline phase could be prepared by the sol-gel method which used the butyl titanate, strontium acetate and barium acetate as the basic raw material and the different concentrations of the glycol ether. The two kinds of gels as the precursors did the hydrothermal reaction under the same condition that the precursors insulated12hours under230℃, the mineralizing agent is the2mol/L of KOH as well as85%of the fullness. The precursors and the corresponding hydrothermal products were characterizated by the FTIR, XRD and SEM. Study the different phases and morphologies of the hydrothermal products which caused by the two kinds of gels. The results showed that the precursor of the amorphous gel produced the nano-powder of BST only, the precursor of the gel containing anatase TiO2crystalline phase generated the nano-powder and the one-dimensional crystal of BST. One-dimensional barium strontium titanate crystals is40um-200um long with a diameter of about lum, and it covered with large quantities of powder. The dispersant was prepared by the0.1%sodium hexametaphosphate, the pH value of the solution was10, the mixed solution was vibrated by ultrasonic wave, and then the one-dimensional crystal of BST was separated from the nano-powders.One kind of the coprecipitation which contained anatase phase as well as other kinds of phases was synthesized by adding directly the butyl titanate, strontium acetate and barium acetate into the deionized water. The another kind of the coprecipitation which contained many phases except anatase was prepared by the mixture of the strontium acetate and barium acetate and the sol which could be got by watering bath butyl phthalate solution. The two kinds of coprecipitation’s phases were detected by XRD. The two kinds of coprecipitation s as the precursors did the hydrothermal reaction under the same condition, and the hydrothermal products were characterizated by the XRD and SEM. The results showed that the precursor of the coprecipitation which contained anatase phase produced the nano-powder and the one-dimensional crystal of BST, and the other precursor generated the nano-powder of BST only. To observe the growth of the one-dimensional crystal of BST and explore its growth mechanism, The first coprecipitation was operated with the different hydrothermal times.The precursor which was the mixture of the anatase nanocrystals and the amorphous gel generated the nano-powder and the one-dimensional crystal of BST by the hydrothermal react. Also, the other precursor which was the mixture of the anatase nanocrystals and the coprecipitation which did not contained anatase phase generated the nano-powder and the one-dimensional crystal of BST through the hydrothermal react. The one-dimensional crystal of BST was detected by HRTEM and SAED, the results showed that the one-dimensional crystal of BST was monocrystal, and its growth plane was the plane of (001) which was coherency with anatase’s plane of (001).To completely separated the one-dimensional barium strontium titanate crystal and powder, the one-dimensional barium strontium titanate crystals was prepared by two-step hydrothermal methed. First, one-dimensional anatase crystal was synthesized by hydrothermal methed according to a literature, and then using the precursor that was mixed by the one-dimensional anatase crystal and overmuch strontium acetate and overmuch barium acetate did hydrothermal experiment, and the hydrothermal products was the mixture of one-dimensional barium strontium titanate crystal and the powders of strontium carbonate and barium and strontium carbonate. One-dimensional barium strontium titanate crystal was obtained by washing the mixture products using acid solution.