Phase Composition Vibrational Infrared and Raman Spectroscopy

Phase Composition Vibrational (Infrared and Raman) Spectroscopy 

Infrared spectroscopy exploits the fact that molecules absorb specific frequencies that are characteristic of their structure. These absorptions are resonant frequencies, that is the frequency of the absorbed radiation matches the transition energy of the bond or group that vibrate. The energies are determined by the shape of the molecular potential energy surfaces, the masses of the atoms and the associated vibronic coupling. 

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In this chapter common methods to evaluate chemical properties and phase composition of bioceramic coatings will be briefly described that are available in many laboratories including X-ray diffraction (XRD), vibrational spectroscopy techniques such as infrared (FTIR) and Raman spectroscopy and nuclear magnetic resonance spectroscopy (NMR). These methods provide a host of information on bulk phase composition, degree of crystallinity and crystallite size. Some special techniques including cathodoluminescence serve to reveal intrinsic coating properties that cannot be assessed by conventional analytical techniques, for example to distinguish between amorphous calcium phosphate (ACP) and crystalline calcium phosphates. 

Lattice dynamics in bulk perovskite oxide ferroelectrics has been investigated for several decades using neutron scattering [71-77], far infrared spectroscopy [78-83], and Raman scattering. Raman spectroscopy is one of the most powerful analytical techniques for studying the lattice vibrations and other elementary excitations in solids providing important information about the stmcture, composition, strain, defects, and phase transitions. This technique was successfully applied to many ferroelectric materials, such as bulk perovskite oxides barium titanate (BaTiOs), strontium titanate (SrTiOs), lead titanate (PbTiOs) [84-88], and others. 

Vibrational spectroscopy [infrared (IR) and Raman] is a powerful technique from which reliable information about chemical composition and stmcture of matter in the solid, liquid, or gas phase can be obtained in a nondestructive way and, in many cases, without any previous sample preparation. Moreover, using Raman or IR microscopy samples in the range of 1-20 pm can be analyzed, which, in the case of pigments, leads to the observation of individual mineral grains. These characteristics place microspectroscopy as unique tool among the different analytical tools available at the present [6-9]. 

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