鋱 (Tb)

發現史

發現: 1843 · Carl Gustaf Mosander

Swedish chemist Carl Gustaf Mosander discovered terbium in 1843. He detected it as an impurity in yttrium oxide, Y2O3, then known as yttria. Yttrium, erbium, and terbium are all named after the village of Ytterby in Sweden. Terbium was not isolated in pure form until the advent of ion exchange techniques. Mosander first separated yttria into three fractions, all named for the ore: yttria, erbia, and terbia. "Terbia" was originally the fraction that contained the pink color, due to the element now known as erbium. "Erbia", the oxide containing what is now known as terbium, originally was the fraction that was yellow or dark orange in solution. The insoluble oxide of this element was noted to be tinged brown, and soluble oxides after combustion were noted to be colorless. Until the advent of spectral analysis, arguments went back and forth as to whether erbia even existed. Spectral analysi

用途與應用

世界上大部分的鋱以氧化鋱的形式用於陰極射線管和日光燈中的綠色磷光體。黃綠色的鋱磷光體加上紅色的三價銪磷光體和藍色的二價銪磷光體，可產生「白」光。通過調節不同磷光體的比例，可以產生不同色溫的白光。這種螢光系統一般應用在螺旋型日光燈泡中。一些電視機和電腦螢屏也同樣使用這種系統作為其三個原色。釹鐵硼磁鐵中的部分釹可以替換為鋱和鏑，以提高矯頑力，從而改善磁鐵的耐熱性能，用於電動汽車的驅動馬達等性能要求較高的應用上。鋱元素或鋱合金具有磁致伸縮性，會感應磁場的強度和方向而改變長短，能將任何物體表面轉變成擴音器。例如將鋱合金棒的一端壓入木桌，並施加強度隨音訊大小改變的磁場（纏繞線圈），金屬棒的外形變化能振動整張桌子，使桌面成為巨大的音訊傳遞表面，達到擴音效果。一般擴音器因阻抗匹配無法如此炮製，鋱合金是極少數能有此應用的物質。由鋱、鏑和鐵組成的Terfenol-D合金是常溫下已知磁致伸縮性最強的材料，被應用在執行器、海軍聲納系統、傳感器、SoundBug揚聲器等設備中。鋱被用作氟化鈣、鎢酸鈣和鉬酸鍶等固態元件所使用的材料之摻雜劑，也與二氧化鋯一同用作在高溫下運作的燃料電池之晶體穩定劑。鋱的螢光特性還被用於檢測內生孢子，當鋱和內生孢子特有的大量吡啶二羧酸結合後，在紫外線燈的照射下會產生光致發光現象，將內生孢子顯示為明亮的綠色螢光斑點。此法除了可以檢測太空飛行器及空間站中微生物的存在，還可以幫助軍隊檢測致病細菌，例如炭疽病的病原體，並且在醫療、製藥和其他領域也具有很好的應用前景。

同位素

Naturally occurring terbium is composed of its only stable isotope, terbium-159; the element is thus mononuclidic and monoisotopic. Thirty-nine radioisotopes have been characterized from 135Tb to 174Tb. The most stable synthetic radioisotopes of terbium are 158Tb, with a half-life of 180 years, and 157Tb, with a half-life of 71 years. All of the remaining radioactive isotopes have half-lives that are less than three months, and the majority of these have half-lives that are less than half a minute. The primary decay mode before the most abundant stable isotope, 159Tb, is electron capture, which results in production of gadolinium isotopes, and the primary mode after is beta minus decay, resulting in dysprosium isotopes. It is also the heaviest element where every stable nuclide has no confirmed energetically allowed decay mode, though the heaviest element with any such isotopes is dyspro