Influence of Non-Stoichiometric Defects on Electrooptics in KNbO3

✍ Scribed by I.V. Kityk; M. Makowska-Janusik; A. Majchrowski

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 218 KB
• Volume: 221
• Category: Article
• ISSN: 0370-1972
• DOI: 10.1002/1521-3951(200010)221:2<815::aid-pssb815>3.0.co;2-n

✦ Synopsis

We present a band energy approach for a total energy cluster optimization which accounts for the various structural modifications caused by the non-stoichiometry of KNbO 3 crystals. The variation of the optical properties with the deviation from the stoichiometric composition can be understood within this approach. The special role of the electron±phonon contributions to the electrooptic coefficient is shown. In particular, model calculations yield a large dependence of the electrooptic coefficient r 22 on the crystal composition, in agreement with the experimental data. The observed experimental minimum of the linear electrooptic coefficient r 22 in the plot versus degree of nonstoichiometry is interpreted as being due to a diminishing in the non-centrosymmetry of the electrostatic potential around [NbO 6 ] clusters.