Kinetic Crossover from Continuous to Discontinuous Behavior in the Incommensurate Phase of Quartz

The α-inc-β transitions of quartz: A century of research on displacive phase transitions

“…Following the interpretation of Lederer, Jamet and Motambaux (1986) in the case of similar effects in thiourea, they are attributed to the diffusion of mobile impurities. -Finally a new spectacular effect has recently been discovered by Mogeon, Dolino and Vallade (1989): when the rate of temperature variation is slow enough the variation of physical properties becomes discontinuous and presents a regular staircase variation as shown in Figure 2. This effect is also attributed to the coupling of the modulation wave with mobile defects.…”

Origin of the Opalescence at theα−βTransition of Quartz: Role of the Incommensurate Phase Studied by Synchrotron Radiation

“…In addition for Ny, we measure the LS from a HeNe laser beam, at an incidence of 3 with respect to the Z axis [8], focused in the middle of the sample at the same height as the x-ray beam. The quartz sample is placed in the furnace used for previous optical and x-ray measurements of the quartz inc phase with a temperature resolution of 1 mK [18]; however, there is a vertical temperature gradient of about 0:1 K=cm along the sample.An overview of the -inc phase transition in the sample Sx is presented in Fig. 1.…”

Temperature dependence of optical activity and circular dichroism in α‐ZnP2 crystals

“…As a consequence, it is a matter of question if the mentioned structure transformations can be detected in the temperature dependence of the gyration, at least with the accuracies, the scan rates _ T T and the samples used in the experiments [5,9]. So, it is known that the needed rates are often as low as _ T T ' 10À10 2 mK/h [22,23,25]. At the same time, a dependence of the main features of q meas ðTÞ on thermal prehistory of samples and the scan rate _ T T, together with a presence of the hysteresis under the conditions of certainly homogeneous temperature distribution in samples at low _ T T may be regarded as a substantiation of the existence of incommensurate modulation in a-ZnP 2 , obtained by the optical methods.…”

“…It is known [30] that the spontaneous changes of the linear birefringence in the course of incommensurate phase transitions are mainly associated with the changes in the order parameter amplitude, and the similar is expected for the optical activity. The manifestations of evolution of the modulation phase in the optical properties may depend on the temperature scan rate and the concentration of structural defects in sample, owing to a finite mobility of the soliton structure and its coupling to those defects (see [22,23,25]). As a consequence, it is a matter of question if the mentioned structure transformations can be detected in the temperature dependence of the gyration, at least with the accuracies, the scan rates _ T T and the samples used in the experiments [5,9].…”

“…Keeping in mind a possible influence of incommensurate modulation on the optical properties of a-ZnP 2 , we have studied the gyration under the conditions of changing the temperature rate _ T T, circling and stabilizing the temperature (see [8,[22][23][24]). Some of the results are presented in Fig.…”