用Ｒａｍａｎ散射研究了四方钽铌酸钾单晶的顺电铁电结构相变，在相变时发现和分析了一个凝聚的软晶格振动模ｖ５，它是产生于Ｏ２Ｏ３键的对称弯曲振动。 The phase transition of the paraelectric-ferroelectric structure of the tetragonal tantalum potassium niobate single crystal was studied by Raman scattering. During the phase transition, a condensed soft lattice vibration mode v5 was found and analyzed. It is a symmetric curve generated by the O2O3 bond vibration.