A piezoelectric single crystal and piezoelectric and dielectric application parts using the same are provided, which have all of high dielectric constant K3T, high piezoelectric constants (d33 and k33), high phase transition temperatures (Tc and TRT), high coercive electric field Ec and improved mechanical properties and thus can be used in high temperature ranges and high voltage conditions. Furthermore, the piezoelectric single crystals are produced by the solid-state single crystal growth adequate for mass production of single crystals and the single crystal composition is developed not to contain expensive raw materials so that the piezoelectric single crystals can be easily commercialized. With the piezoelectric single crystals and piezoelectric single crystal application parts, the piezoelectric and dielectric application parts using the piezoelectric single crystals of excellent properties can be produced and used in the wide temperature range.