  The fluorite to pyrochlore phase transition in La2Zr2O7 has been studied in
the literature for decades in the context of thermal barrier coatings and
reinforcement materials. However, the nature of the phase transition in this
system is still not well understood. In this article we have investigated the
phase transition in La2Zr2O7, calcined at different temperatures, using powder
x-ray diffraction and Raman measurements. Rietveld analyses of the x-ray data
suggest a fluorite to pyrochlore phase transition in the system occurring
between 1000-1450oC. Nonetheless, Raman spectra, recorded with different
excitation wavelengths (\lambda_ex) reveal that the dynamics of phase
transition is different in the near-surface region and in the bulk inside.
While the near-surface region carried the signatures of a pure pyrochlore
phase, the temperature dependent Raman measurements with \lambda_ex=785 nm
suggest that locally formed oxygen related disordered states are present in the
bulk of the system.
