Raman studies of TGS doped with Nd

https://doi.org/10.1016/S0022-3697(00)00081-0Get rights and content

Abstract

Monocrystals of triglycine sulfate (TGS) doped with Nd, were studied by Raman spectroscopy. HeNe laser radiation (632.817 nm) was used as the illumination source. The spectra were dispersed with a resolution of 1 cm−1/pixel. The observed lines were assigned to the vibrations of the characteristic groups and valence bonds in the investigated samples. Doping of TGS with Nd does not cause a change in the crystal structure and the symmetries of groups in the unit cell remain unaffected. A new mode at 1535 cm−1 appeared for all crystals doped with Nd, which indicates that Nd is coordinated with the glycine molecule. Doping with Nd affects significantly the C–CO bending mode at 584 cm−1, the O–C–O bending mode at 665 cm−1, the SO42− mode at 1086 cm−1 and the CH2 wagging and twisting mode at 1310 cm−1. The Raman bands at 1374 and 1413 cm−1 indicate the presence of a zwitterion, which supports Hoshino's theory for spontaneous polarization reversal in TGS.

Introduction

Triglycine sulfate (NH2CH2COOH)H2SO4 (TGS) and its isomorphs form an important group of room temperature ferroelectrics. Single crystals of TGS are considered to be the most suitable materials for developing pyroelectric detectors of infrared radiation [1], [2], [2]. A disadvantage of these crystals is the tendency of their polarization to spontaneous reversal. Therefore, studies dealing with the influence of doping TGS crystals on their physical properties are of particular interest. In recent years, the interest in studying pure and doped TGS crystals has increased [4], [5], [6], [7], [8] because of their promise in various devices. Such applications include environmental analysis monitors, earth observation cameras, astronomical telescopes, medical vidicons, military systems, laser beam characterization, and Fourier Transform Infrared (FTIR) instrumentation. The devices have a number of very important characteristics such as low cost, low power requirement, and a wide range of operating temperature and frequency response [9].

Raman and IR studies of pure and doped TGS crystals have been carried out [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20]. However, we are unaware of any publication that deals with Raman studies of TGS under the influence of admixtures of rare-earth ions.

The availability of the rare-earth elements is of great interest to scientists doing basic research. Rare-earths are generally accepted to be the elements between 58 and 71, inclusive [21], [22]. In the elements in this part of the periodic table, as the charge on the nucleus increases, the balancing electrons fill in the inner incomplete 4f subshell. Since the 4f electrons are well screened by the completed 5s5p subshells, they play almost no role in the valence forces, although they do play a very important role in some physical properties [22]. Information obtained from Raman studies of rare-earth doped TGS may be important to characterize the second-order transition in TGS monocrystals.

Section snippets

Experimental

Pure and doped single TGS crystals were grown by the dynamical method in the ferroelectric phase [23]. All samples used in these experiments were grown from aqueous solution. The dopant salt was in the form of sulfate. The concentration of Nd2(SO4)3 in the solution was 10, 20 and 30% for the different monocrystals. Table 1gives the electronic configurations of the dopant atom and derived tripositive ion.

The samples for the present investigations were plates, cleaved perpendicular to the polar

Results

Raman spectra of pure and Nd-doped TGS modes were recorded from 90 to 3100 cm−1 (Fig. 2, Fig. 3, Fig. 4, Fig. 5). By using the spectral data of SO4, CH2, NH3, C–H and by comparing the spectra of the different samples, we assigned the observed lines to the vibrations of the characteristic groups and valence bonds in the investigated samples (Table 2). The observed Raman lines are compared with those cited in the literature. Most of our assignments agree with previously reported values [10], [11],

Discussion

It is difficult to interpret the low-frequency spectrum because the character of external vibrations of TGS is determined mainly by the system of hydrogen bonds between structural elements of this crystal. The vibration with the frequency 137 cm−1 for pure TGS and 141, 139 and 138 cm−1 for the Nd-doped crystals, respectively, is a typical lattice vibration of sulfate groups, since in a simple sodium sulfate—Na2SO4, has a band [26] with the same frequency—140 cm−1. We assign the low-frequency

Conclusions

  • 1.

    A new mode at 1535 cm−1 appeared for all crystals doped with Nd, which confirms that Nd is coordinated with the glycine molecule.

  • 2.

    Doping with Nd affects significantly the C–CO bending mode at 584 cm−1, the O–C–O bending mode at 665 cm−1, the SO42− mode at 1086 cm−1 and the CH2 wagging and twisting mode at 1310 cm−1.

  • 3.

    Doping of TGS with Nd does not cause a change in the crystal structure, and the symmetries of groups in the unit cell remain unaffected.

  • 4.

    The Raman bands at 1374 and 1413 cm−1 indicate the

References (27)

  • N. Kaneko et al.

    J. Phys. Chem. Solids

    (1977)
  • T. Sundius et al.

    J. Mol. Struct.

    (1989)
  • G. Sivanesan et al.

    Mater. Chem. Phys.

    (1993)
  • A. Sakai et al.

    Physica B

    (1996)
  • J. Novotny et al.

    J. Cryst. Growth

    (1971)
  • B.K. Choi et al.

    Solid State Commun.

    (1989)
  • F. Schwarz et al.

    Appl. Opt.

    (1970)
  • E.H. Putley
    (1970)
  • Y.H. Xu

    Ferroelectric and Piezoelectric Materials

    (1978)
  • J. Martinez et al.

    Ferroelectrics

    (1982)
  • S. Mielcarek et al.

    Ferroelectrics

    (1988)
  • M.A. Gaffar et al.

    J. Phys. D: Appl. Phys.

    (1989)
  • E. Mihaylova et al.

    Ferroelectrics

    (1995)
  • Cited by (23)

    • Preferences of polarity and chirality in triglycine sulfate crystals by alanine ghost

      2021, Journal of Physics and Chemistry of Solids
      Citation Excerpt :

      Various compounds-doped TGS crystals have been long studied in efforts to enhance the ferroelectric, pyroelectric, and/or piezoelectric properties. Most amino acids [24–27], the other organic compounds [28–30], metal ions [31,32] and rare-earth ions [33–35] have been widely used as dopants. Alanine-doped TGS (ATGS) crystals grown from TGS solutions containing alanine have received considerable attention; such crystals exhibit improved pyroelectric properties [36].

    • Effect of rare earth Nd<sup>+</sup> ion on the growth, structural, spectral, optical and mechanical properties of piperidinium p-hydroxybenzoate single crystals

      2016, Optik
      Citation Excerpt :

      Doping of heavy rare-earth ions like Ho+, Tm+ and Yb+ has created the structure and chemical defects in the crystal and also known that the defect density depends on the electronic configuration of the rare-earth ions [14]. In the case of light rare-earth ion doping, the crystal structure remains unaltered [15]. In this report, neodymium nitrate (Nd+) was added to piperidinium p-hydroxybenzoate (PPHB) as the dopant material and systematic studies were performed on the growth, structure, morphology, thermal, optical, mechanical and etching properties of Nd+ ion doped PPHB crystal.

    • Growth and characterization of l-glutamic acid and sodium sulphate doped tri glycine sulphate single crystal

      2014, Journal of Industrial and Engineering Chemistry
      Citation Excerpt :

      This substitution creates an internal bias field into TGS by which the crystal becomes permanently polarized [5–7]. Various studies and methods of doping using amino acid [8–10], rare-earth ions such as La, Ce, Nd [11–13], have been adopted to increase the ferroelectric behaviors of TGS and the effects of has been reported. Substitution of amino acid is found to increase the phase transition temperature and also improve the dielectric behavior.

    • Effect of rare earth ions on the properties of glycine phosphite single crystals

      2013, Journal of Crystal Growth
      Citation Excerpt :

      Effect of rare earth metals plays a vital role in improving the physical properties of organic ferroelectric materials such as TGS, TGSe and BPI [5,6]. Many efforts were made in the past to understand the growth mechanism, to improve the piezoelectric, pyroelectric, mechanical, optical and ferroelectric properties of ferroelectric materials and to prevent depolarization [7–9]. Doping with heavy rare earth (Ho, Tm and Yb) ions create structural and chemical defects in the crystals, whereas in the case of light rare earth ion doping, the crystal structure remains unaltered however, growth aspects, morphology, domain structure and hysteresis behavior altered significantly.

    View all citing articles on Scopus
    View full text