Disordered state in IC(incommensurate)-and N(normal)-phases of Ca₂CoSi₂O₇deduced from variation of thermal displacement factors

Thermal and electromechanical properties of melilite-type piezoelectric single crystals

“…On the other hand, for Ca 2 MgSi 2 O 7 crystals, d 14 is decreased from 5.3 pC/N to 1.7 pC/N with temperature increasing from 25 C to 500 C. The bond lengths of Ca-O were reported to increase with increasing temperature, with different variation levels for different Ca-O bonds, 26 leading to a certain degree of tilt for CaO 8 antiprisms, which may account for the decreased d 14 . Piezoelectric coefficient d 36 was found to decrease prior to the incommensurate-normal phase transition point T ic-N , above which, it is increased.…”

“…19 Thus, the longer bond length of Ca-O, the larger the distortion/rotation of tetrahedrons, giving rise to larger d 36 value. It should be noted that some of the Ca-O bond lengths in Ca 2 MgSi 2 O 7 are decreased from room temperature to T Ic-N , 26 measured by the impedance method with d 14 being on the order of 5.3-9.3 pC/N. The relationship between microstructure and electromechanical properties of CNG, CGS, and CMS was established, which will benefit the exploration of the piezoelectric origin in melilite crystals.…”

Single crystal growth and electron microscopy studies of Co/Zn-melilites with modulated structure

“…These changes are accompanied by changes of the interlayer X-cation environment in a way that reduces the coordination number of X from eight to seven or even six [7][8][9][10]. It is further assumed that the flattened T 1 -tetrahedra surrounded by low-coordinated X cations show the tendency to form octagonal clusters, and that the arrangement of these clusters determines the strength of the overall modulation [4,9,11].…”

Stimulated emission (4F3/2 → 4I11/2 channel) with LD and Xe-flashlamp pumping of tetragonal, incommensurately modulated Ca2MgSi2O7:Nd3+(Na+) - a new disordered laser crystal

“…The microprobe measurements reveal molar fractions x = 0.007 of Nd 3+ and x = 0.013 of Na + thus showing that the distribution coefficients for Nd 3+ and Na + are different and both < 1. Two orthogonal linear scanning measurements across [33] five-dimensional space group P421m : p4mg Modulation wave vectors [33] k1 Fig. 2) consisting a short semi-confocal resonator and a 5-W fiber-coupled LD (Unique-Mode, UM7800-100-20) with a 100 mm core diameter and 0.22 NA at ≈ 0.807 μm wavelength as a pumping source.…”

“…in [21]. The incommensurate modulation of the crystal structure of IC -Ca 2 MgSi 2 O 7 at room temperature is described to result from a misfit of the sheets of [ As a consequence, a slight distortion of the tetrahedral coordination polyhedra and a strong alteration of the coordination of Ca is found, with Ca coordinated by either six, seven or eight oxygen ligands [33].…”