The crystals of LnP_5O_(14) were grown by evaporation solution method. Some big crystalsof LnP_5O_(14) with better optical properties have been made under suitable conditions. The properties and some rules of LnP_5O_(14) crystals have been studied.With the in-crease of the atomic number,the density of LnP_5O_(14) increases,while the average distanceof Ln-O bonds and the decomposition temperature decrease and susceptibility appears tochange periodically.The infrared spectra of LnP_5O_(14) show that the P-O b...