S. Leela et al. / Spectrochimica Acta Part A 77 (2010) 927–932
931
Fig. 7. TGA/DTA spectrum of the MDMABA.
to nonlinear refraction [27]. Such a scheme, referred to as an “Open
aperture” Z-scan, is suited for measuring nonlinear absorption in
the sample. Results obtained from a typical open aperture Z-scan
study for the grown MDMABA crystal are presented in Fig. 6. The
nonlinear absorption coefficient (ˇ) of the crystal was calculated
using the standard relations given below [26–28]
ues with the applied load is shown in Fig. S4. The hardness value
increases with increasing load. The plane considered for study
exhibits the reverse indentation size effect. The specimen thus leads
to a larger indentation size which gives rise to a lower hardness at
low loads [29]. For loads above 100 g, cracks started developing
around the indentation mark. It is concluded that the hardness of
the MDMABA crystal is moderately good.
√
ˇ = 2
2 ꢂT
(2)
I0Leff
4. Conclusion
where Leff = [1 − exp(−˛L)]/˛ with I = P/(ꢃω02) defined as the peak
0
intensity within the sample, where L is the thickness of the sample,
and ˛ is the linear absorption coefficient. The enhanced transmis-
sion near the focus is indicative of the saturation of absorption
at high intensity. The focusing effect is attributed to a thermal
nonlinearity resulting from absorption of radiation at 532 nm.
Localized absorption of a tightly focused beam propagating through
an absorbing medium produces a spatial distribution of tempera-
ture in the crystal and, the value of nonlinear absorption coefficient
Our results show the potential use of combinatorial synthe-
sis for obtaining targeted libraries in materials chemistry. The
title compound might be utilized as an active dopant in polymer
based second harmonic generating, electro optic or photorefractive
materials. The UV–vis–NIR spectrum elucidates that the crystal is
transparent between 370 and 1200 nm. From the FTIR, FT-Raman
and NMR spectra, the formation of the imine group of the mate-
rial was confirmed. Thermal analyses indicated that the crystal has
good thermal stability. The hardness of the crystal was recorded.
High-resolution X-ray diffraction study shows that the perfection
of the crystal is fair even though it contains a low angle boundary.
The Z-scan technique carried out showed that the relative third
order nonlinear optical absorption coefficient is 0.18539 cm/W.
(
ˇ) estimated is 0.18539 cm/W.
3.8. Thermal analysis
The thermogravimetric analysis (TGA) of MDMABA was carried
◦
◦
out between room temperature (30 C) and 1200 C at a heating
rate of 10 K/min. The experiment was performed in a nitrogen
Acknowledgements
◦
atmosphere. The material is stable up to 250 C after which decom-
position starts and it shows that there are no water molecules in the
One of the authors (SL) thanks Dr. A. Ilangovan, School of
Chemistry, Bharathidasan University, Tiruchirappalli for fruitful
discussions. SL also thanks Dr. Reji Philip, Associate Professor,
Raman Research Institute, Bangalore, India for Z-scan studies. One
of the authors (SL) thanks to Dr. C.K. Magadevan for Dielectric stud-
ies and the fertile discussion. The authors thank the University
Grants Commission, Government of India [File No. 32-37/2007 (SR)]
for financial assistance.
◦
compound. A major weight loss (88%), which starts at 250 C and
◦
ends at 420 C, is attributed to the loss of carbonyl compounds. The
second weight loss is due to the loss of nitrogen molecules between
◦ ◦
30 C and 820 C. The material is fully decomposed at the tempera-
ture of 1100 C. A sharp endothermic peak at 145.6 C corresponds
to the melting point. The sharpness of the peak reveals the good
crystallinity of the synthesized compound, and is shown in Fig. 7.
4
◦
◦
3.9. Mechanical property
Appendix A. Supplementary data
The structure and composition of the crystalline solids are
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.saa.2010.08.012.
related to the mechanical hardness. Microhardness testing is one of
the best methods to understanding mechanical properties of mate-
rials such as fracture behavior, yield strength, brittleness index, and
temperature of cracking. The measurements were done at room
temperature for different forces. The measurements were made on
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