Influence of iron concentration on its structural position in KNbO3 lattice

✍ Scribed by N.V. Cherney; V.A. Nadolinny; E.G. Boguslavsky; V.N. Shlegel

• Book ID: 104420587
• Publisher: Elsevier Science
• Year: 2001
• Tongue: English
• Weight: 278 KB
• Volume: 4
• Category: Article
• ISSN: 1369-8001
• DOI: 10.1016/s1369-8001(02)00040-9

✦ Synopsis

In this paper variations of structural positions of Fe 3+ ions in KNbO 3 crystals depending on iron content in growth components have been studied by the ESR method. Crystals of KNbO 3 have been grown by the Czochralski method. In addition to finding two EPR spectra published by Siegel we have found two novel types of paramagnetic centers (I, IV) caused by incorporation of iron impurity. One of them is observed at the low concentration of iron impurity. This center (I) has C 3V symmetry, S ¼ 5=2 and is due to incorporation of Fe 3+ ions into the potassium positions of regular lattice. Increasing iron content in growth mixture up to 200 ppm resulted in disappearance of this center and two ESR spectra (II, III) described by Siegel arose. Limited content of (II) and (III) iron-containing defects is due to a restricted solubility of iron in KNbO 3 crystal. An increase of iron content in growth mixture over 400 ppm produces new a type of defectF(IV). This center has C 3V symmetry, electronic spin S ¼ 1=2 and is due to 3d 5 electronic state of Fe 3+ ion in strong crystalline field. The structural models of observed centers are discussed.