Comprehensive Characterization of Niobate Phase Transitions Via Simultaneous on-Chip Differential Scanning Calorimetry (DSC) and in Situ Raman Spectroscopy

This work presents, for the first time, a characterization platform that integrates a high-sensitivity MEMS thermopile chip-based DSC with in situ Raman spectroscopy, enabling correlative analysis of the phase-transition thermodynamics and lattice structural evolution of$\text{KNbO}_{3}$. This integrated approach overcomes the limitations of conventional single-technique characterization methods. Leveraging the high sensitivity and rapid response of the chip-based DSC, the DSC chip successfully and clearly detects the two phase-transition temperatures of nanogram-scale$\text{KNbO}_{3}$, namely the orthorhombic-to-tetragonal transition temperature$(\mathrm{T}_{0-\mathrm{t}}$) at$215.94{}^{\circ} \mathrm{C}$and the tetragonal-to-cubic transition temperature$(\mathrm{T}_{\mathrm{t}-\mathrm{c}}$) at$435.94{}^{\circ} \mathrm{C}$. When integrated into a Raman spectroscopy system for in situ measurements, the results reveal the temperature-dependent evolution of the$\text{KNbO}_{3}$crystal structure during phase transitions. Furthermore, Raman-guided compositional modulation reveals that$\text{LiNbO}_{3}$doping in$\text{KNbO}_{3}$can increase the Curie temperature$(\mathrm{T}_{\mathrm{t}-\mathrm{c}}$) while decreasing$\mathrm{T}_{\mathrm{o}-\mathrm{t}}$. These findings demonstrate that the combination of chip-based DSC and in situ Raman spectroscopy can be used to probe the phase-transition behavior of niobates and guide the compositional engineering of functional perovskite oxides.