Truncated Spline Regression to Estimate Curve of Strontium Titanate XRD Data

Abstract

Characterization of ferroelectric material using X-Ray Diffraction tools (XRD) resulted in 2θ degree angle and intensity of diffraction data. These data showed the relationship between 2θ degree angle and diffraction intensity which formed a spectrum pattern with fluctuation of diffraction intensity values as the increasing of 2θ degree angles. The high fluctuation of diffraction intensity value affected the inconsistency of mean and variance values. The estimation of the spectrum pattern could not be analysed by parametric models which needs strict with assumptions. Spline regression is a polynomial model with flexible segmentation to estimate the curve of XRD data. This research used the truncated spline regression model to estimate the curve of Strontium Titanate (SrTiO3) and SrTiO3 doping with 2% of RuO2 (SrTiO3+RuO2) XRD data. The best curve of SrTiO3 was estimated by the model with 42 knots, while that of SrTiO3+RuO2 was estimated by the model with 37 knots.