Development of the BaO-Mg(Zn) O-Ta_2O_5 ternary phase diagram for single crystal growth of the Ba(Mg_<1/3> Ta_<2/3>) O_3 and Ba(Zn_<1/3> Ta_<2/3>) O_3 using off-stoichiometric composition method

我们完成了BaO-镁(氧化锌)-Ta_2O_5系在1450℃平衡时相关系的研究。在BaO-MgO-Ta2O5系统中发现了三个三元相，即3：1：1钙钛矿型Ba3MgTa_2O_9，9：1：7TTB(四方钨青铜)型，14&gt；O_&lt；45&gt；和4：1：5Ba4MgTa_&lt；10&gt；O_(&t)；30&gt；另一种具有10层六方钙钛矿结构的三元相Ba10Mg0.25Ta7.9O30只有在1600℃平衡后才能得到。Ba9MgTa&lt；14&gt；O&lt；45&gt；相具有量子铁电性质。我们还澄清了关于BaO-MgO-Ta_2O_5组成领域中有关三元和二元相的几个相互矛盾的报道。例如，我们没有发现R.S.Roth所声称的六方相Ba_9 Mg_4Ta_&lt；20&gt；O_&&lt；63&gt；[`实验陶瓷系统的相平衡‘，NIST项目报告，报告第1号，合同号SB1341-02-W-0787，国家标准与技术研究所陶瓷分部；盖瑟斯堡，马里兰州；2页(2003)]，我们也不能确认Ba7Ta_6O_&lt；22&gt；几位作者报告的阶段[J.S.Kim，J.-W.Kim，C.I.Cheon，Y.-S.Kim，S.Nahm，J.D.Byun，J.EUR.塞拉姆。社会科学院，2001，21,2599；郑明训，谢永泰，杨振峰，Ceram.2002，28,255；陈晓明，铃木，N。佐藤，J.科学：电子学中的材料，1994，5,244]。TTB类型的Ba9MgTa；14&gt；O_&lt；45&gt；沿BaTa_2O_6.Ba3MgTa2O9连接部位形成。我们发现，沿Mg_4Ta_2O_9-BaA_2O_6系只存在六方晶型的BaTa_2O_6相，而在BaO-ZnO-Ta_2O_5系中，不能确定存在Ba4ZnTa_&lt；10&gt；O_&lt；30&gt；化合物。取而代之的是沿ZnTa_2O_6-BaTa_2O_6系线发现了Ba3ZnTa_8O_(24)&gt；相。用单晶结构分析证明了Ba3ZnTa8O；24&gt；相与Ba4MgTa；10&gt；30&gt；相是同类型的，并讨论了它们化学成分不同的原因。

We completed investigation of the phase relation in the BaO-MgO(ZnO)-Ta_2O_5 system equilibrated at 1450℃. In the BaO-MgO-Ta2O5 system we found three ternary phases, namely 3:1:1 perovskite Ba_3MgTa_2O_9, 9:1:7 TTB(tetragonal tungsten bronze)-type Ba_9MgTa_<14> O_<45> and 4:1:5 Ba_4MgTa_<10> O_<30> with close relation to the tungsten bronze structure. Another ternary phase, Ba10Mg0.25Ta7.9O30, with 10 layer hexagonal perovskite structure can be only obtained after equilibration at 1600℃. The Ba_9MgTa_<14> O_<45> phase shows quantum ferroelectric properties.We have also clarified several contradictory reports related to the ternary and binary phases in the BaO-MgO-Ta_2O_5 composition field. For example, we found no evidence of the hexagonal Ba_9Mg_4Ta_<20> O_<63> phase that was claimed by R. S. Roth[` Phase Equilibria of Experimental Ceramic Systems', NIST Project Report, Report No.1, Contract No.SB1341-02-W-0787, National Institute of Standards and Technology, Ceramics Division ; Gaithersburg, Maryland ; 2 pp.(2003)], nor we can confirm the existence of the Ba_7Ta_6O_<22> phase reported by several authors[J. S. Kim, J.-W. Kim, C. I. Cheon, Y.-S. Kim, S. Nahm, J. D. Byun, J. Eur. Ceram. Soc., 2001, 21, 2599 ; C.-M. Cheng, Y.-T. Hseih, C.-F. Yang, Ceram. Int., 2002, 28, 255 ; X. M. Chen, Y. Suzuki, N. Sato, J. Mater. Sci.: Materials in Electronics, 1994, 5, 244]. The TTB type Ba_9MgTa_<14> O_<45> forms along the BaTa_2O_6. Ba3MgTa2O9 join. We found that only hexagonal polymorph of the BaTa_2O_6 phase exists along the Mg_4Ta_2O_9-BaTa_2O_6 tie line.In the BaO-ZnO-Ta_2O_5 system we could not confirm the existence of the Ba_4ZnTa_<10> O_<30> compound. Instead, a Ba_3ZnTa_8O_<24> phase has been found along the ZnTa_2O_6-BaTa_2O_6 tie line. Using single crystal structural analysis we have demonstrated that the Ba_3ZnTa_8O_<24> phase is isotypical with the Ba_4MgTa_<10> O_<30> phase and discussed the reasons for the difference in the chemical composition of these phases.