Estimating the diffuseness for the nonrelaxor-type ferroelectric to paraelectric phase transition in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>BaTi</mml:mi> <mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn

The normal ferroelectric to paraelectric phase transition in model ferroelectric materials such as $\mathrm{BaTi}{\mathrm{O}}_{3}$ is typically characterized by a sharp, well-defined dielectric constant peak at a specific transition temperature. However, under certain modifications of the parent material, this transition can become diffuse over a broad range of temperatures. This has garnered significant research attention over the past few decades, primarily because of its intriguing and not yet fully understood physical properties. The parameters developed to measure the diffuseness are also ambiguous. In this Letter, an investigation has been conducted to understand the transition dynamics of the nonrelaxor ferroelectric systems in the temperature interval over which the diffuse phase transition occurs. This is achieved by modeling the dielectric response phenomenologically, using a distribution of local transition temperatures. Moreover, a temperature-dependent differential analysis is introduced, enabling the clear demarcation of distinct dielectric regimes and providing enhanced insight into the evolution of the phase transition. It is strongly recommended that the degree of diffuseness \ensuremath{\gamma} parameter is uncertain in many senses. Hence, following the establishment, a simple yet effective measure of diffuseness is being proposed, offering a more accurate and physically meaningful estimation of the diffuse phase transition.