DOI: 10.5061/dryad.td26kr2
title: Data from: Thermal evolution of the crystal structure and phase transitions of KNbO3

description: The thermal evolution of the crystal structure and phase transitions of
 KNbO3 were investigated by high-temperature powder X-ray diffraction and
 Rietveld refinement of the diffraction data. Two phase transitions from
 orthorhombic (Amm2) to tetragonal (P4mm) and from tetragonal to cubic (Pm3
 ̅m) were confirmed, both on heating and cooling. Both phase transtions are
 first order based on the observed hysteresis. The mixed displacive and
 order-disorder nature of the tetragonal to cubic transition is argued
 based on symmetry and apparent divergence of the atomic positions from
 pseudo-cubic values. The transition between the orthorhombic and
 tetragonal phase show no temperature-dependence for atomic positions and
 only thermal expansion of the unit cell parameters and is thus discussed
 in relation to a lattice dynamical instability.
description: heating1_100-200c_60minX-ray diffraction data in .raw format compatible with Bruker software.heating2_210-650c_60minX-ray diffraction data in .raw format compatible with Bruker software.cooling1_640-150c_60minX-ray diffraction data in .raw format compatible with Bruker software.cooling2_140-40c_60minX-ray diffraction data in .raw format compatible with Bruker software.start_19-60deg_60minX-ray diffraction data in .raw format compatible with Bruker software.end_19-60deg_60minX-ray diffraction data in .raw format compatible with Bruker software.Temperature calibration with aluminaSpreadsheet used to find the real temperature as a function of set point temperature by using the thermal expansion of alumina.T_cal_13_Mai_2016.xlsxRefinement_parameters_Amm2_coolingTable of all refinement parameters for the Amm2 phase of KNbO3 upon cooling. Setpoint temperature can be converted to real temperature by using the temperature calibration file in the same repository.Amm2_Nbfix_Bfix2_SDref_cooling.txtRefinement_parameters_Amm2_heatingTable of all refinement parameters for the Amm2 phase of KNbO3 upon heating. Setpoint temperature can be converted to real temperature by using the temperature calibration file in the same repository.Amm2_Nbfix_Bfix2_SDref_heating.txtRefinement_parameters_P4mm_coolingTable of all refinement parameters for the P4mm phase of KNbO3 upon cooling. Setpoint temperature can be converted to real temperature by using the temperature calibration file in the same repository.P4mm_Nbfix_Bfix2_SDref_cooling.txtP4mm_Nbfix_Bfix2_SDref_heatingTable of all refinement parameters for the P4mm phase of KNbO3 upon heating. Setpoint temperature can be converted to real temperature by using the temperature calibration file in the same repository.Refinement_parameters_Pm3m_coolingTable of all refinement parameters for the Pm-3m phase of KNbO3 upon cooling. Setpoint temperature can be converted to real temperature by using the temperature calibration file in the same repository.Pm3m_Bfix2_SDref_cooling.txtPm3m_Bfix2_SDref_heatingTable of all refinement parameters for the Pm-3m phase of KNbO3 upon heating. Setpoint temperature can be converted to real temperature by using the temperature calibration file in the same repository.