A temperature-dependent Raman spectroscopic study on Bi2 Zn OB2O6crystal was carried out to investigate the structure change of the crystal with the increase of temperature. Raman spectra of crystal Bi2 Zn OB2O6were recorded in the spectral range 10–1600 cm-1at room temperature first. Compared with the vibrational spectra of the referred compounds,satisfactory assignment of most of the high-energy modes to vibrations of Bi–O, B–O, and Zn–O bonds was achieved. In particular, the Raman high-frequency peak located at 1344 cm-1was attributed to the B–O vibration in the BO3 triangle.This temperature-dependent Raman spectroscopic study was carried out up to 600°C. It was found that all the Raman lines exhibit decreases in frequency and the widths of the Raman peaks increase with increasing temperature. No phase transition was observed under 600°C.
The lutetium tantalate compounds obtained from Lu2O3–Ta2O5 with a molar ratio of 0.515 ： 0.485 were studied by Raman scattering and x-ray diffraction. The results of the room temperature Raman scattering indicate that the sample has a phase transition between 1830℃ and 1872℃, the polycrystalline is a mixture of M-LuTaO4 and Lu3TaO7（F m3m）when it is prepared at 1830℃, and a mixture of M-LuTaO4（B112/b） and Lu3 Ta O7（Fm3^-m） when it is prepared at above 1872℃. The sample melts at a temperature of 2050℃. The phase transition of the sample prepared at 2050℃ was also investigated by the high-temperature Raman spectra, and the result indicates that no phase transition occurs between room temperature and 1400℃, which is consistent with the results from the x-ray diffraction.
Raman spectra of a vanadoborate （Na3VO2B6Oll） crystal from room temperature up to the melting point have been recorded. The main internal vibrational modes of the crystal have been assigned. It was found that all the Raman bands exhibit decreases in frequency and the widths of the Raman bands increase with the increase of temperature. However, no phase transition was observed under 525 ℃. The micro-structure of its melt was studied by quantum chemistry ab initio calculation. The continuous three-dimensional network of the crystal collapsed and transformed into VO4 and VBO6 clusters during the melting process with an isomerization reaction from four-coordinated boron to a three-coordinated species.
The Judd-Ofelt theoretic transition intensity parameters A（tp）k of luminescence of rare-earth ions in solids are important for the quantitative analysis of luminescence.It is very difficult to determine them with emission or absorption spectra for a long time.A ＂full profile fitting＂ method to obtain A（tp）k in solids with its emission spectrum is proposed,in which the contribution of a radiative transition to the emission spectrum is expressed as the product of transition probability,line profile function,instrument measurement constant and transition center frequency or wavelength,and the whole experimental emission spectrum is the sum of all transitions.In this way,the emission spectrum is expressed as a function with the independent variables intensity parameters A（tp）k,full width at half maximum（FWHM） of profile functions,instrument measurement constant,wavelength,and the Huang-Rhys factor S if the lattice vibronic peaks in the emission spectrum should be considered.The ratios of the experimental to the calculated energy lifetimes are incorporated into the fitting function to remove the arbitrariness during fitting A（tp）k and other parameters.Employing this method obviates measurement of the absolute emission spectrum intensity.It also eliminates dependence upon the number of emission transition peaks.Every experiment point in emission spectra,which usually have at least hundreds of data points,is the function with variables A（tp）k and other parameters,so it is usually viable to determine A（tp）k and other parameters using a large number of experimental values.We applied this method to determine twenty-five A（tp）k of Yb（3＋） in GdTaO4.The calculated and experiment energy lifetimes,experimental and calculated emission spectrum are very consistent,indicating that it is viable to obtain the transition intensity parameters of rare-earth ions in solids by a full profile fitting to the ions＇ emission spectrum.The calculated emission cross sections of Yb（3＋）：GdTaO4 a
Profile function properties with different variables are discussed, the formulae of stimulated absorption, spontaneous and stimulated emission, absorption and emission coefficients, and cross sections are deduced, and some confusing issues are clarified.
