Thermal analysis, Raman spectroscopy and complex impedance analysis of Cu2+-doped KDP

Abstract

Raman spectroscopy and differential thermal analysis (DTA) and thermogravimetric analysis have been carried out on Cu-doped KH 2 PO 4 (Cu-KDP). X-ray diffraction powder data reveal that the structure of the KDP crystal does not change with the additive Cu 2+ ion. DTA analysis and Raman study of Cu-KDP as a function of temperature reveal that this compound undergoes two phase transitions at about Ttr =453 and 473 K. The electrical conductivity measurements on polycrystalline pellet of Cu-KDP (5) are performed from room temperature (RT) up to 495 K. Only one phase transition is observed at 470 K. The activation energy in the migration is 0.42 eV in the temperature range from RT to 470 K. For temperature above 470 K, the activation energy of the superprotonic phase is 1.87 eV.

Water vapor pressure over molten KH2PO4 and demonstration of water electrolysis at ∼300 °C

“…Spectra at higher temperatures in the monoclinic phase similar to our spectra have been obtained before [24,25,28,29,33,34], including a peak at 1175 cm -1 . The broad peaks at about 1830, 2390 and 2710 cm -1 have also been seen [20,33,34] and were related to the intermolecular hydrogen bond network. Signs of dehydration composition were seen at high temperatures and pressures [28,29], and it may be that there exists another solid phase before the melting.…”

“…The room temperature Raman bands of KH 2 PO 4 have been assigned carefully, based on orientated single crystal studies at room temperature [21,[26][27][30][31] and calculations have been also done [36]. Spectra at higher temperatures in the monoclinic phase similar to our spectra have been obtained before [24,25,28,29,33,34], including a peak at 1175 cm -1 . The broad peaks at about 1830, 2390 and 2710 cm -1 have also been seen [20,33,34] and were related to the intermolecular hydrogen bond network.…”

“…The Raman spectra of KDP phases have been studied many times in previous literature in dependence of conditions such as temperature, pressure, chemical composition and preparation techniques. Limiting ourselves here to Raman spectra at room and higher temperatures there are still many studies available [20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. There is a consensus that the crystal structure at room temperature is tetragonal (space group I42d) and that the structure transforms to monoclinic (space group P1, P2 1 /c or P2 1 /m) at temperatures at about 180-200 o C. The transformation to this lower symmetric phase is well documented by many techniques and the decomposition of the KH 2 PO 4 to KPO 3 + H 2 O has been taken into account, see e.g.…”

Effect of UV Laser Conditioning on the Structure of KDP Crystal

“…According to Som et al, the peak observed at 114 cm −1 may be assigned to K-PO 4 translatory vibrations [22]. The peak at 181 cm −1 can be assigned to the H 2 PO 4 rotational band [21]. The strongest peak at 914 cm −1 can be assigned to PO 4 totally symmetric stretching mode [23].…”

Temperature Dependence of Soft Mode Frequency, Dielectric Constant and Loss Tangent in Deuterated KDP Crystal

“…Strukov et al 3 have made hysteresis loop and specific heat studies on KDP and DKDP crystals. Ettomi et al 4 have made thermal analysis studies on KDP and DKDP crystals. Chai et al 5 have made Raman scattering studies on KDP and DKDP crystals.…”