Synthesis, Thermal Analysis, Spectroscopic Properties, and Degradation Process of Tutton Salts Doped with AgNO3 or H3BO3.

In this work, we synthesized and studied the spectroscopic properties of (NH4)2(SO4)2Y(H2O)6 (Y = Ni, Mg) crystals doped with AgNO3 or H3BO3. These crystals constitute a series of hexahydrated salts known as Tutton salts. We investigated the influence of dopants on the vibrational modes of the tetrahedral ligands NH4 and SO4, octahedral complexes Mg(H2O)6 and Ni(H2O)6, and H2O molecules present in these crystals through Raman and infrared spectroscopies. We were able to identify bands that are attributed to the presence of Ag and B dopants, as well as band shifts caused by the presence of these dopants in the crystal lattice. A detailed study of the crystal degradation processes was performed by thermogravimetric measurements, where there was an increase in the initial temperature of crystal degradation due to the presence of dopants in the crystal lattice. Raman spectroscopy of the crystal residues after the thermogravimetric measurements helped us to elucidate the degradation processes occurring after the crystal pyrolysis process.

Electronic properties and vibrational spectra of (NH4)2M″(SO4)2·6H2O (M = Ni, Cu) Tutton's salt: DFT and experimental study.

The complex crystals of the family of the Tutton's salt have been investigated through the numerous experimental and theoretical studies to understand their physical properties and their potential technological applications. In spite of the more than 60 years of research, there are very few studies about the electronic properties of Tutton's salt. In our present work, we have calculated the stability, electronic properties and the first theoretical study of band structure of the three different crystals of the Tutton's salt, ammonium nickel sulfate hexahydrate ((NH4)2Ni(SO4)2·6H2O), ammonium nickel-copper sulfate hexahydrate ((NH4)2Ni0.5Cu0.5(SO4)2·6H2O) and ammonium copper sulfate hexahydrate ((NH4)2Ni(SO4)2·6H2O) with the help of periodic ab-initio calculations based on density functional theory (DFT). In addition to this, the internal Raman and FTIR modes of the ionic fragments [Ni(H2O)6]2+, [Cu(H2O)6]2+ NH4+ and SO42- of the sample crystals were obtained by employing the ab initio and the orientation of the molecular vibrations of the ionic fragments have been presented in picturized form. Furthermore, the Raman and FTIR spectroscopy of the sample crystals were measured in the range 100-4000 cm-1 and 400-4000 cm-1 respectively, and the internal vibrational modes obtained from experimental measurement have been compared with those obtained from DFT calculations.

Volume dependence in Handel's model of quartz crystal resonator noise.

Although criticized by many, Handel's quantum model for 1/f noise remains the only model giving a quantitative estimation of the level of intrinsic 1/f noise in quartz crystal resonators that is compatible with the best experimental results. In this paper, we reconsider the volume dependence in this model. We first argue that an acoustic volume, representing the volume in which the vibration energy is trapped, should be used instead of the geometrical volume between the electrodes. Then, we show that because there is an implicit dependence of the quality factor of the resonator with its thickness, the net effect of Handel's formula is not an increase of noise proportionally to the thickness of the resonator, as could be naïvely expected, but a net decrease when thickness increases. Finally, we show that a plot of Q(4)Sy versus the acoustic volume, instead of the usual Sy plot, could be useful to compare the quality of acoustic resonators having very different resonance frequencies.