此研究是以R123(R = 鑭系元素，但不含Ce、Pm和Tb)起始物的混合粉體作為樣品，利用 TG-DTA 在不同氣氛與升溫速率下，控制粒徑大小，量測生成反應起始溫度 (Tonset) 並計算活化能。R123的 Tonset隨著升溫速率、氧分壓與R離子所含4f未成對電子數的增加而上升。以外插法推測Tonset在氮氣、空氣與氧氣下，升溫速率接近於零時的R123的生成反應溫度分別為813—854、846—879和869—903℃。依Kissinger、Reich與Ozawa法計算所得活化能也隨著氧分壓上升而增加。Ozawa法所得活化能與R離子所含4f未成對電子數也呈線性增加。在氮氣、空氣與氧氣氣氛下所得的活化能範圍分別是239—575、531—666與716—840 kJ/mole。Ozawa法計算活化能是將生成反應分為10段處理；Kissinger與Reich法是以單一的溫度或重量變化計算活化能，因此，前者所得結果與R離子的未成對電子數關係較明顯，研判此法較適於分析R123的生成反應。 The precursor powder of R123 (R = lanthanides, except Ce, Pm and Tb) were mixed. Its formation reaction was investigated by TG-DTA in different atmospheres. Particles size, heating rate and oxygen partial pressure were controlled to measure the formation temperature (Tonset) and the activation energy was calculated. Tonset was increased with increasing the heating rate, oxygen partial pressure and the number of the 4f unpaired electrons of the R ion. Extrapolating the reaction rate to zero heating rate, Tonset was found in the range of 813—854, 846—879 and 869—903℃, respectively under the N2, air and O2 atmospheres. The activation energy (Ea) of the R123 formation reaction was increased with increasing the oxygen partial pressure according to the Kissinger, Reich and Ozawa method. Ea was also linearly increased with increasing the number of the unpaired 4f electrons of the R ion calculated by the Ozawa method. They were in the range of 239—575, 531—666 and 716—840 kJ/mole with respect to the N2, air and O2 atmospheres. By the Ozawa method, reaction was separated into 10 parts to calculate the activation energy. Instead, by the Kissinger and Reich method, one temperature or weight change was used for the calculation. It seems that the former is a better solution for calculating the activation energy of the formation reaction of the R123.