High-pressure investigations of lanthanoid oxoarsenates: I. Single crystals of scheelite-type <i>Ln</i>[AsO<sub>4</sub>] phases with <i>Ln</i> = La–Nd from monazite-type precursors
作者:Sebastian J. Metzger、Florian Ledderboge、Gunter Heymann、Hubert Huppertz、Thomas Schleid
DOI:10.1515/znb-2015-0210
日期:2016.5.1
scheelite-type Ln[AsO4] phases with Ln = La–Nd are obtained by the pressure-induced monazite-to-scheelite type phase transition in a Walker-type module under high-pressure and high-temperature conditions of 11 GPa at 1100–1300 °C. Coinciding with this transition, there is an increase in density and a reduction in molar volume of about 4.5 % for the scheelite-type phases (tetragonal, I41/a) for La[AsO4] (a = 516
摘要 在高压和高温条件下,通过压力诱导独居石到白钨矿型相变,在 Walker 型模块中获得了白钨型 Ln[AsO4] 相的透明单晶,其中 Ln = La–Nd在 1100–1300 °C 时为 11 GPa。与这种转变同时发生的是,La[AsO4](a = 516.92(4), c = 1186.1)的白钨矿型相(四方晶系,I41/a)的密度增加,摩尔体积减少约 4.5% (9) pm), Ce[AsO4] (a = 514.60(1), c = 1175.44(2) pm), Pr[AsO4] (a = 512.63(4), c = 1168.25(9) pm), 和 Nd [AsO4] (a = 510.46(4), c = 1160.32(11) pm) 与众所周知的独居石型相(单斜,P21/n)相比。令人惊讶的是,白钨型氧砷酸盐 (V) 的 Ln3+ 阳离子的配位数较低(CN = 8