Karakterisasi mikrostruktural material penyerap gelombang elektromagnetik senyawa LaxBa(1-x)Fe0.25Mn0.5Ti0.25O3, (x = 0, 0.25, 0.75, 1) = Microstructural characterization of LaxBa(1-x)Fe0.25Mn0.5Ti0.25O3, (x = 0, 0.25, 0.75, 1), an electromagnetic wave absorbance material