Curie temperatures and dielectric properties of doped and undoped KTiOPO/sub 4/ and isomorphs

The Curie temperatures and dielectric properties of KTiOPO(4 ) (KTP), RbTiOPO(4), KTiOAsO(4), RbTiOAsO(4 ), CsTiOAsO(4), Ba:KTP, and Ga:KTP were measured with small-signal relative dielectric permittivity (kappa) analysis, piezoelectric resonance analysis, and optical second harmonic generation. All the isomorphs and the doped KTP exhibit lower Curie temperatures than KTP, ranging from 637 degrees C for CsTiOAsO(4) to 955 degrees C for hydrothermally (HT) grown KTP. The Curie-Weiss law is obeyed in all samples. With the exception of CsTiOAsO(4), all doped and undoped crystals show large dielectric relaxation at frequencies below 100 KHz throughout the temperature range of 500 degrees C-800 degrees C. For the barium-doped KTP, it was found that the Curie temperature decreases with increasing Ba(++)-doping concentration. Barium doping also significantly modifies dielectric and piezoelectric properties of KTP.