ELSEVIER zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Synthetic Metals 71 (1995) 1615-1616 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLK Electrosynthesis of barium potassium lead oxide single crystals L. Z. Zhao, J. B. Zhang, D. B. Zhu Institute of Chemistry, Academia Sinica, Beijing, 100080, China B. Yin, J. W. Li, C. Dong, Z. X. Zhao Institute of Physics, Academia Sinica, Beijing, 100080, China Abstract Single crystals of barium potassium lead oxide (BKPO) h ave been synthesized using an anodic electrocrys- tallization method. The resulting crystals have been characterized by using XRD, XPS, ICP-AES and magnetic method. l.INTRODUCTION Norton1 has developed a molten salt electrocrys- tallization method for preparation of single crystals of Bao,sK” .4Bi03 superconductor at a low temperature. This method is particular powerful because the process selects only the most conductive phases, while electro- chemical growth of insulating phases is self-limited. With little modification, this method affords the oppor- tunity to synthesize other temperature sensitive materi- als. Here we report for the first time on the electrocrys- tallization and characterization of Ba-K-Pb-O(BKP0) single crystals. 2.ELECTROCRYSTALLIZATION The starting materials were analytical grade potas- sium hydroxide, barium hydroxide and lead nitrate in which excess potasium hydroxide was used as a flux. The typical atomic ratio of Ba:K:Pb in the molten salt composition was about 1.5:50:1. The starting materials were loaded into a new Teflon crucible and melted at 250 “ C!. Two electrodes were used for electrochemical crystal growth. The anode was a platinum wire and the cat,hode .was a gold wire. A constant current source was used in the experiments and the typical cell current w as 4mA. Crystal growth was performed at 250 “ C in air. The typical deposition times were between 22 and 46h and yielded faceted crystals 3-4mm on an edge. The crystals produced are air cooled, w ater rinsed, and 0379-6779/95/$09.50 0 1995 Elsevier Science S.A. All rights rem SSDI 0379-6779(94)02976-6 then soaked in distilled water. After immersed the crys- tals into distilled water for about 10 minutes, the crys- tals were observed to change color from black to blue. After immersed into water for about 30 minutes, the samples are taken out and rinsed with alcohol, and then allowed to air dry. 3.CHARACTERIZATION X-ray photoelectron spectroscopic (XPS) analysis were performed on BKPO samples using an ES300 elec- tron spectrometer. The strong atomic signals from Ba, K. Pb and 0 were recorded. No impurity atoms were detected within the XPS detection limit(O.OOl-0.01) ex- cept carbon atoms from contaminants. Special atten- tion has been paid to determination of the possible Bi impurity. ICP-AES analysis has revealed that there are trace Bi impurity in BKPO samples. However, the Bi concentrations are only in the range of O.Ol%-0.05% (wt%). It is obvious that the trace Bi is mostly from impurities in the starting materials. As already no- ticed, the electrocrystallization method is to favor the migration of Bi towards the growing electrode. The Ba:K:Pb ratio in BKPO single crystals, de- termined by chemical analysis, was found to be about 0.9:0.1:1. This result combined with the result of the structure analysis indicates that the chemical composi- tion of BKPO single crystals is about Bao.gKo.lPbOs. Powder X-ray diffraction patterns of Bao.9 Ko.1 PbOs sample were made by using MXP18A-HF diffrac- ved