Electric properties of KTiOPO4 and NaTiOPO4 from temperature-dependent X-ray diffraction

• Published in: Journal of applied crystallography Vol. 32; no. 1; pp. 1 - 10
• Main Authors: Dahaoui, S., Hansen, N. K., Protas, J., Krane, H.-G., Fischer, K., Marnier, G
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01-02-1999; Blackwell
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Dielectric properties of solids and liquids; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Exact sciences and technology; Inorganic compounds; Physics; Polarization and depolarization; Pyroelectric and electrocaloric effects; Salts; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Phosphates; Temperature dependence; Titanyl compounds; Inorganic compounds; Potassium compounds; Transition element compounds; Ionic conductivity; Pyroelectricity; XRD; Experimental study; Charge distribution; Monocrystals; Electron density; Quaternary compounds; Electrostatic potential; Spontaneous polarization; Sodium compounds; Crystal structure
• ISSN: 1600-5767; 0021-8898; 1600-5767
• DOI: 10.1107/S002188989800497X

Single crystals of KTiOPO4 (KTP) and NaTiOPO4 (NaTP) show pronounced pyroelectric behaviour. In order to determine the origin of this property on an atomic scale, X‐ray diffraction measurements have been carried out at several temperatures between 100 and 600 K. Modelling of the electron density and the evolution of the structure as a function of temperature has enabled the determination of values for the spontaneous polarization of the compounds and the pyroelectric coefficient of KTP, principally due to the alkaline‐ion displacements with a value of 2.0 nC cm−2 K−1. Structure modifications, compared with NaTiOPO4, and the calculation of the electrostatic potential explain the anisotropic behaviour of ionic conductivity of KTP single crystals.