应用低稀释比，即低熔剂-样品质量比的方法熔融样品为X射线荧光光谱（XRFS）分析制备了测试样品，提出了铌钽原矿及精矿的XRFS分析方法。选择质量比为12比22的四硼酸锂和偏硼酸锂作为混合熔剂，熔剂与样品的质量比为4比1的条件下熔融矿样。应用TNRY-01C型全自动熔样机，并选择如下熔样条件：称取样品2.000 g及混合熔剂8.000 g，置于铂-金（质量比95：5）坩埚中，搅拌均匀，滴加饱和溴化锂溶液0.15 mL，于1 200℃熔融180 s，摆动240 s，静置20 s，待样片自然冷却后翻转，补加饱和溴化锂溶液0.05 mL，按上述条件重复熔融1次。此熔融方法对铌钽氧化物质量分数不小于0.01%的原矿和铌钽氧化物质量分数不小于60%的精矿均能很好熔化。若仅考虑铌、钽分析，熔融时间影响可予忽略，无需统一。对于一些难熔样品可适当延长熔融时间，但需注意补充溴化锂溶液。若需测定样品中碱金属及卤族元素，则需保持一致的熔融时间。上述操作中加入了复熔步骤是为了消除气泡，使样片表面光滑平整，并能保证样品熔化完全。在所测定的11项组分中，常量组分测定值的相对标准偏差（n=6）均小于1.0%，微量组分测定值的相对标准偏差（n=6）不超过4.0%。

Low dilution fusion, i.e. fusion of sample with low mass ratio of flux to sample, was used as sample preparation for use in XRFS analysis of crude ore and concentrate containing niobium and tantalu. Optimum conditions for sample fusion were studied thoroughly and reported in detail. A mixture of lithium tetraborate and lithium metaborate in the mass ratio of 12 to 22 was used as flux. Mass ratio of the flux mixture to sample of 4 to 1 was taken for the fusion, and the optimum conditions were chosen as follows:2.000 g of the ore sample were mixed thoroughly with 8.000 g of the mixed flux in a Pt-Au (w_Pt:w_Au=95:5) crucible. After addition of 0.15 mL of saturated lithium bromide solution, the fusion was carried out with TNRY-01C automatic sample fusion melter at 1 200℃ for 180 s, the crucible was swung for 240 s and then stayed for 20 s. When the melt was cooled down naturally, the melt disc of the sample was turned over and the fusion was repeated once under the same conditions described above, with a supplementary addition of 0.05 mL of saturated lithium bromide solution. By the above fusion process either the crude ore samples containing ≥ 0.01% of niobium tantalum oxide or the concentrate sample containing ≥ 60% of niobium tantalum oxide can all be well melted. In case only analysis of ores containing Nb and Ta is considered, effects of time of fusion can be ignored, but in case of some ore samples hard to melt, the fusion time can be prolonged, with attention to supplementary addition of LiBr solution. In case of analysis of ore samples containing alkali metals or halogens, definite and consistent time of fusion should be kept. The purpose of the re-fusion process mentioned above were ① to expel gas bubbles from the melt in order to keep a plain and smooth surface of the melt; and ② to ensure a complete melting of the sample. Precision of determination of the 11 components in the ore samples was tested, values of RSDs (n=6) <1.0% were found for the major components and ≤ 4.0% for those micro-components.