**2.3. Characterization**

acid solution (CH3

76 Ferroelectrics and Their Applications

**2.2. Sample preparation**

*2.2.1. Biopolymeric films*

*2.2.2. Bio-ferroelectric nanocomposites*

the polymeric matrix.

in the matrix.

(CH3 CO<sup>2</sup> CO<sup>2</sup>

H, 99.7 + %, Alfa Aesar) while 4-methylmorpholine N-oxide solvent

nanoparticles.

H, 99.7 + %, Alfa Aesar) was needed to dissolve the cellulose powder. The fabrica-

tion of the composites consisted of two subsequent stages: (1) fabrication of chitosan-cellulose

To prepare the specimens, one must considered their adequate size for the ensuing characterization. In particular, special care was taken to better the uniform distribution of the particles

The biopolymeric films consisted of a mixture of chitosan and cellulose, prepared by means of the solution casting technique. To prepare the chitosan solution, a fixed concentration of the polymer (1.5 v%) was dissolved in an acetic acid aqueous solution and mechanically stirred. Furthermore, the cellulose solution was made by adding the polymer into a 4-Methylmorpholine N-oxide (NMMO) solvent, followed by mechanical stirring at 65°C to enhance the polymer solubility. A fixed concentration of cellulose, i.e., 0.5 v%, was used for the preparation of the composites. A higher concentration of cellulose would have raised the water content, which could have been detrimental for the resulting electrical, mechanical, and thermal properties. After the stock solutions of chitosan and cellulose were prepared separately, we readied smaller stock solutions with different volume percentages of chitosan and cellulose: 85 v%Ch-15 v%Cel and 75 v%Ch-25 v%Cel. After mixing the components, we mechanically stirred the solutions, poured them into petri dishes, and let them dry in an oven at 40°C. Afterwards, we removed the films from the petri dishes using a basic solution and dried them in an oven once again [7].

The double layered bio-ferroelectric composites were fabricated layer-by-layer via the solution casting method. The first layer consisted of chitosan-cellulose bio-polymers and the second layer consisted of the bio-polymers mixed with strontium titanate (STO) particles. To fabricate the said first layer, small solutions of chitosan and cellulose (i.e., 85 v%Ch-15 v%Cel and 75 v%Ch-25 v%Cel) were synthesized and transferred in the petri dishes for the dry process. The purpose of the second layer was to prevent the nanoparticles from settling and passing through the still soft first polymeric film. Hence, for the second layer, the same amount of small solutions was synthesized, this time with different STO amounts, i.e., 10 and 20 wt%; the goal was to analyze their effect in the electrical properties of the resulting biocomposites. Thereafter, these solutions were transferred onto their corresponding first layer of chitosan-cellulose followed by a second drying process to remove any residual water from

The dispersion of nanoparticles within a given matrix has always been an issue, as proven in a prior research [11]. Therefore, to enhance such dispersion in the matrix we reduced the size of the particles using a varioplanetary high energy ball mill. To find the optimal time in which

films, and (2) synthesis of chitosan-cellulose composites containing SrTiO<sup>3</sup>
