Divalent impurity ions in potassium tantalate crystals: EPR investigations.

Electron paramagnetic resonance experimental results of potassium tantalate single crystals doped by Co2+ ions as well as new results of our continuous studies of KTaO3:Cu single crystals are presented. Divalent impurity ions substitute for Ta5+ in the octahedron position in the KTO3 crystal and oxygen vacancies are required to compensate the extra charge of Ta5+. The Cu2+ ions associated with oxygen vacancies form only axial centres (included exchange coupled pair centre), the symmetry axes being along cubic directions. A new axial centre of Co2+ in the crystal of KTaO3:Co has been studied