Existence Of Ferroelectricity Research Articles

Dielectric and Electrical Behavior of Apraseodymium Based Tungsten Bronze Ceramics

AbstractThe ceramic oxide Na2Ba2Pr2W2Ti4Nb4O30 (NBPWTN) is prepared by a mechanical mixed oxide route. The compound formation and the phase are concluded from the x‐ray diffraction pattern taken at room temperature (XRD). The uniform distribution of grains of various sizes with negligible voids is studied from scanning electron micrograph of the sample pellet. The presence of dielectric dispersion and ferroelectric phase in the material is observed from the temperature‐dependent dielectric parameters at selected frequencies. The existence of ferroelectricity in the material is further confirmed by the room temperature hysteresis loop. Impedance spectroscopic studies informed about the correlation between the microstructure and electrical behavior. The frequency variation of AC conductivity refers to Jonscher's law. The temperature variation of frequency exponent term n indicates OLPT (overlapping large polaron‐tunneling) model of the conduction mechanism in the sample. NBPWTN is a strong candidate for applications involving thermistor‐related devices because of the temperature dependency of resistance. The value of temperature sensitivity coefficient β in our investigation is achieved between 2000 and 11 000 K, confirming that the material has a high‐temperature stability property and is ideal for high‐temperature electronics applications. The high room temperature dielectric constant value of the ceramic (around 500) is useful for dielectric capacitor applications.

Studies of Structural, Optical, and Electrical Properties of Eco‐Friendly Complex Ferroelectrics: BaTiO3–Bi0.5Na0.5TiO3

Some lead‐free complex compounds containing the two perovskite compounds BaTiO3 and Bi0.5Na0.5TiO3 of chemical composition (Ba1–xBix/2Nax/2)TiO3 (x = 0, 0.05, 0.1, 0.15) are fabricated using a cost‐effective mixed oxide method. Synthesis and characterization (electrical, ferroelectric, and optical) of the above‐defined complex ferroelectrics are reported in this article. Analysis of the X‐ray diffraction data/pattern reveals the formation of phase pure compounds with tetragonal symmetry. Determination of particle size is done using the Scherrer formula. A morphology study of sintered (at 1100 °C) pellets indicates that average grain size decreases with an increase in Bi/Na content of Bi0.5Na0.5TiO3. Studies of Fourier transform infrared spectroscopy and ultraviolet–visible–near‐infrared spectroscopy reveal the type of chemical bonds present in the materials. The energy bandgaps of the compounds are found to be suitable for optical device applications. The frequency and temperature dependence of the dielectric study reveals that the dielectric constant increases and loss tangent decreases with an increase in Bi/Na content of Bi0.5Na0.5TiO3. The analysis of the I–V plot and the field‐dependent polarization (P–E hysteresis loop) provide the low leakage current and existence of ferroelectricity at room temperature, respectively.

Tuning electrical properties of BaTiO3 with iron modification

BaTiO3 plays an important role in advanced functional devices owing to its fascinating properties. Though it is an excellent ferroelectric material, its magnetism can be switchable via suitable modification. In this report, we have studied iron-modified BaTiO3, which has been prepared using cost-effective high-temperature solid-state reaction techniques. The Fe-modified BaTiO3 maintains its crystallinity in the tetragonal phase with P4mm space group with a slight variation of tetragonality ratio to 1.002 from 1.008 of BaTiO3 of the identical synthesis method. This is confirmed by Rietveld refinement. Field emission scanning electron microscopy (FESEM) and EDX (energy dispersive X-rays) spectrum along with an elemental mapping analysis has provided the feature of the Fe-modifed BaTiO3. Atomic force microscope (AFM) has been employed to get the detailed surface topology (2D and 3D) and surface roughness of the developed systems. This deformation caused by the incorporation of Fe significantly modifies the electrical properties of barium titanate. The ferroelectric-paraelectric phase transition temperature (Tc) of Fe-modified BaTiO3 has been diffused and shifted to 300 °C from 120 °C of pure BaTiO3, suggesting the materials for the high-temperature capacitive application. The room temperature M-H hysteresis of Fe-modified BaTiO3 indicates the ferromagnetism developed in the BaTiO3 with the introduction of Fe. The ac conductivity is in the order of 10−4 Ω−1cm−1, and its frequency response obeys Jonscher's power law. Different charge carriers are responsible for diverse conduction processes in different temperature ranges confirmed by the Arrhenius plot. Impedance spectroscopy studies reveal the existence of NTCR characteristics of the developed system. Well defined ferroelectric hysteresis loop indicates the existence of ferroelectricity in the developed system. The analysis of various electrical parameters has provided information on the material's dielectric relaxation and conduction mechanisms for possible application in functional devices.

The Ferroelectric-Ferroelastic Debate about Metal Halide Perovskites.

Metal halide perovskites (MHPs) are solution-processed materials with exceptional photoconversion efficiencies that have brought a paradigm shift in photovoltaics. The nature of the peculiar optoelectronic properties underlying such astounding performance is still controversial. The existence of ferroelectricity in MHPs and its alleged impact on photovoltaic activity have fueled an intense debate, in which unanimous consensus is still far from being reached. Here we critically review recent experimental and theoretical results with a two-fold objective: we argue that the occurrence of ferroelectric domains is incompatible with the A-site cation dynamics in MHPs and propose an alternative interpretation of the experiments based on the concept of ferroelasticity. We further underline that ferroic behavior in MHPs would not be relevant at room temperature or higher for the physics of photogenerated charge carriers, since it would be overshadowed by competing effects like polaron formation and ion migration.

Dielectric and complex impedance characteristics of lead free BaBiSb3Ti4O15 compound

BaBiSb3Ti4O15 is a Bi-based Sb substituted Barium Bismuth Titanate ceramic is processed by mixed oxide process, calcined at 850 °C and subsequently sintered at 875 °C temperature. Room temperature XRD study confirms the formation of single-phase compound. The SEM micrograph shows uniformly distributed grains over the surface of the compound. Dielectric characteristic is studied in a wide frequency (100 Hz–10MHz) and temperature (30 °C–500 °C) range. Phase transition broadening is observed on substitution of antimony ion at bismuth site indicating diffuse phase transition in the material. From the appearance of P ∼ E loop, the existence of ferroelectricity in the material is confirmed. The complex impedance plots inform the impact of the grain and grain interface in the resistive and capacitive behavior of the compound. Negative temperature coefficient of resistance (NTCR) characteristics are noticed from the impedance study confirming the semiconductor-like behavior of the compound.

Origin of ferroelectricity in carbon-doped ZnO nanocolumnars: Experimental and density-functional studies

One-dimensional ZnO exhibits high polarization but is considered to be non-ferroelectric. Here, we show ferroelectricity in carbon-doped ZnO nanocolumnars deposited using one-step DC-unbalanced magnetron sputtering. Doping carbon effectively increases its lattice strain and turns the ZnO nanocolumnars into a ferroelectric material. The existence of a reversible permanent electric dipole is found from the P–E hysteresis loop of the carbon-doped ZnO nanocolumnars, where the highest coercivity (11.1 kV/cm) originated from zinc vacancies and remnant polarization (4.7 μ C/cm 2 ) originated from oxygen vacancies. Moreover, the presence of carbon modified the optical bandgap of the system. Supporting the experimental results, the first-principle calculation shows that the increment of C concentration decreases bandgap contributed by C 2p . Furthermore, the existence of ferroelectricity in ZnO has the potential to bring out the multiferroic properties for developing next-generation ZnO-based storage devices.

Studies of structural, dielectric and impedance spectroscopy of Sr/ Zr modified BiFeO3 ceramics

Bismuth ferrite (BiFeO3) is the most commonly used multiferroics for multifunctional applications. The polycrystalline samples of co-doped (Sr/Zr) bismuth ferrite (BiFeO3) of a general chemical composition, Bi1-xSrx)(Fe1-xZrx)O3, x = 0.05, 0.1, 0.15, 0.20, were prepared using a standard solid-state reaction method. The basic structural data of the above synthesized electro-ceramics were obtained by X-ray diffraction data and pattern. The surface morphology of the samples was recorded at room temperature by a scanning electron microscope. The scanning electron microscope images show the uniform distribution of grains throughout the surface of the samples. Studies of dielectric and impedance properties of the samples at varying frequency (1 kHz–1000 kHz) and temperature (250C–300 °C) have provided many important information about the materials. The existence of ferroelectricity in the materials was studied by the electric field dependent polarization. The contributions of both grains and grain boundaries towards the total resistance and capacitive behavior of the compounds have been studied by analyzing the frequency and temperature dependence of impedance data.. Study of frequency-temperature dependence of ac-conductivity has provided the information on the type of conduction mechanism. The J–E characteristics of the samples provide the Ohmic behavior with slope closer to 1.

Interplay between charge ordering and geometric ferroelectricity in LuFe2O4/LuFeO3 superlattices

Oxide superlattices have drawn great attention owing to the intriguing coupling among elastic, electrical, and magnetic orderings at the interfaces and the emergence of improper ferroelectricity. Here, superlattices composed of hexagonal $\mathrm{LuFe}{\mathrm{O}}_{3}$ $(\mathrm{h}\text{\ensuremath{-}}\mathrm{LuFe}{\mathrm{O}}_{3})$ and $\mathrm{Lu}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ are investigated via density functional theory calculations. h-$\mathrm{LuFe}{\mathrm{O}}_{3}$ is a well-known multiferroic material that is stable only in thin film or doped bulk state, while $\mathrm{Lu}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ is a charge ordered (CO) material where the existence of ferroelectricity is still a controversy. We have found that the CO-induced polarizations in $\mathrm{Lu}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ layers coexist with the geometric polarizations in $\mathrm{h}\text{\ensuremath{-}}\mathrm{LuFe}{\mathrm{O}}_{3}$ layers in the ${(\mathrm{Lu}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4})}_{m}/{(\mathrm{LuFe}{\mathrm{O}}_{3})}_{n}$ superlattices with different periodicities, and the ferroelectric states are generally preferred over the antiferroelectric states for $\mathrm{Lu}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ in superlattices. The out-of-plane polarizations in h-$\mathrm{LuFe}{\mathrm{O}}_{3}$ and $\mathrm{Lu}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ layers tend to be aligned in parallel, and the overall polarization increases with the ratio of $\mathrm{h}\text{\ensuremath{-}}\mathrm{LuFe}{\mathrm{O}}_{3}$. The influence of layered polarizations on the local electrostatic potential is not significant except the detected small trend caused by the CO-induced polarization within a FeO bilayer. Additionally, the local electronic structures show that the Fermi level position in a certain layer can be tuned by the valences of Fe in this layer and the polarization distributions in neighboring layers. $\mathrm{Lu}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ layers sandwiched between thick $\mathrm{h}\text{\ensuremath{-}}\mathrm{LuFe}{\mathrm{O}}_{3}$ layers are more susceptible. The calculated configurations of the superlattices are supported by atomic-resolution transmission electron microscopy experiments. Our results pave the way for tunable ferroelectricity in superlattice systems and create a playground for manipulating the coupling between various degrees of freedom.

A literature review of the research on ferroelectric polymers

In this work, the research and development of ferroelectric polymers has been reviewed. The main focus is on properties of different types of ferroelectric polymers. Ferroelectrics of ceramic and thin film nature, are widely known for their use in several electronic devices. But the existence of ferroelectricity in polymers has made the ferroelectric polymers to be used in different electrical applications such as sensors, actuators, etc. The main theme of this paper is to report only the existing literature on ferroelectric-polymeric materials.

Studies of structural, dielectric and impedance spectroscopy of Ca/Zr modified BiFeO3 ceramics

In this communication, the structural and electrical (dielectric, polarization, impedence, and conductivity) properties of the polycrystalline samples of Ca/Zr modified BiFeO3 samples with chemical formula (Bi1-xCax) (Fe1-xZrx)O3; x = 0.05, 0.1, 0.15, 0.20 were prepared using a solid-state reaction method at 800 °C have been reported. The analysis of room temperature X-ray diffraction data of above-synthesized electro-ceramics confirms the formation of single phase perovskite in rhombohedral phase. The scanning electron microscope photographs provide the micro-structural study of the samples. The existence of ferroelectricity in the materials was studied by the variation of electric polarization with the applied electric field. Many important results have been obtained from the dielectric and impedance studies of the samples at a varying frequency (1 kHz–1000 kHz) and temperature (250C–300 °C). The contribution of both grains and grain boundaries towards the total resistance and capacitance of the four compounds is found from the Nyquist plots. From the conductivity study, the dielectric properties and conductivity of the materials were obtained. The J–E characteristics of the samples provide the Ohmic behavior with slope closer to 1.

Structural, dielectric and electrical properties of BiFeO3 and BaTiO3 modified Bi(Mg0.5Ti0.5)O3

Bismuth barium magnesium ferric titanate (Bi0.5Ba0.5) (Mg0.125 Ti0.625 Fe0.25)O3 is fabricated through a standard ceramic technology route. By using various experimental techniques, the material has been characterized. Study of crystal structure using XRD (X-ray diffraction) data shows the rhombohedral system. Analysis of dielectric study reveals that the compound has low tangent loss and high dielectric constant at room temperature. At low frequencies and high temperatures, the existence of space charge polarization and the Maxwell–Wagner dielectric mechanism in the material has been realized. The existence of ferroelectricity in the material is confirmed by the PE loop. The impedance plots reveal that the compound shows semiconductor (based on negative temperature of coefficient of temperature) behavior at high temperature ≥ 300 °C. Analysis of Nyquist plots reveals the non-Debye type of dielectric relaxation and the contribution of grains and grain boundaries in the resistive and capacitive nature of the material. From the conductivity analysis, it can be seen that the sample obeys the Josher universal power law, and the Arrhenius type of conductivity. The low-leakage current of compound makes it suitable for the high temperature applications, and hence it shows probable Ohmic-type of conduction mechanism.

Studies of structural and electrical properties of lead-free ceramic: Bi(Ba0.25Ti0.25Fe0.5)O3

Bismuth barium ferric titanate Bi(Ba0.25Ti0.25Fe0.5)O3 has been fabricated through a conventional solid-state reaction route. By means of various experimental techniques, the material has been characterized in different experimental conditions. Study of crystal structure using X-ray diffraction data determines the tetragonal system. The detailed studies of dielectric, impedance, conductivity of Bi(Ba0.25Ti 0.25Fe0.5)O3 in a broad range of temperature (25 – 380°C) and frequency (1kHz –1MHz) have provided a range of exciting results on structure and correlation properties, conduction mechanism, etc. The existence of ferroelectricity in the material is confirmed by the polarization-electric field loop analysis. At low-frequencies and high- temperatures, space charge polarization and the Maxwell–Wagner dielectric relaxation have been observed. The grain and grain boundary effects in the ceramic sample have been studied from the Nyquist plots. The study of temperature-frequency dependence of transport properties (conductivity) of the specimen has established type of conduction mechanism in it. The coefficient of magneto-electric coupling of the studied sample is found to be 3.79 mV cm−1Oe−1 at null magnetic field.

Structural, dielectric, thermal and electrical characteristics of lead-free double perovskite: BiHoZnCeO6

BiHoZnCeO6, the double pervoskite was synthesized using a cost-effective solid-state reaction method. The structural evaluation of the double pervoskite, when carried out by using the X-ray diffraction pattern suggested an orthorhombic crystal geometry with non- centrosymmetry space group Pca21. The microstructural investigation on the above material is carried out with the help of a scanning electron micrograph. These SEM micrographs showed that the grains of varying sizes (0.5–2 μm) are uniformly distributed. The study of dielectric characteristics as a function of temperature and frequency revealed some interesting characteristics of the material. One such observation is the identification of ferroelectric transition temperature at 435 °C. The strong anomaly at 435 °C and the ferroelectric behavior of the material is further validated by the study of spontaneous polarization (the hysteresis loop). In the present communication, the detailed microstructural, dielectric (dielectric constant, tangent loss, and electric polarization), thermal and electrical (impedance, electrical modulus, conductivity) studies on bismuth holmium zinc ceranate is presented along with the existence of ferroelectricity.

Research progress of two-dimensional interlayer-sliding ferroelectricity

In recent years, the existence of ferroelectricity in a series of two-dimensional van der Waals materials has been experimentally confirmed, in which the ferroelectricity induced by interlayer sliding is an important type. This mechanism is not available in traditional ferroelectrics but can be applied to many two-dimensional materials. In this paper we review the relevant researches and introduce the origin of this type of ferroelectricity: in many two-dimensional van der Waals bilayers, the upper layer is not equivalent to the lower layer, thus giving rise to a net interlayer charge transfer and the inducing vertical polarization to be switchable via interlayer sliding. This unique sliding ferroelectricity can widely exist in many van der Waals bilayers, multilayers and even bulk structures. The interlayer sliding barrier is several orders of magnitude lower than that of traditional ferroelectric, which may greatly save the energy required by ferroelectric switching. At present, this type of interlayer sliding ferroelectricity has been experimentally confirmed in WTe<sub>2</sub> and <i>β</i>-InSe bilayer/multilayer systems, and more systems predicted to be with much stronger interlayer sliding ferroelectricity (like BN) may be realized in near future.

Structural, dielectric, impedance, and modulus spectroscopy of BaSnO3-Modified BiFeO3

A BaSnO3-modified BiFeO3 compound (i.e., Bi0.95Ba0.05Fe0.95Sn0.05O3) was synthesized by a cost-effective mixed-oxide reaction method at 850 °C. The solubility of 5% BaSnO3 in BiFeO3 (BFO) and the formation of a single-phase compound in the rhombohedral structure was checked by the Rietveld refinement method using the X-ray diffraction data. The analysis of Fourier transform infrared (FTIR) spectra reconfirmed the formation of the compound. The temperature-dependent dielectric spectrum for the sample exhibits a broad anomaly at 190 °C, which seems to be the superposition of three Gaussian peaks corresponding to the Maxwell–Wagner effect, as well as the oxygen-vacancy-induced Fe2+/Fe3+ and Sn2+/Sn4+ redox mechanism. A sharp peak at 350 °C corresponds to the magnetic reordering around the Néel temperature. Complex impedance spectroscopy along with modulus analysis confirmed the deviation from Debye-type behavior. The Cole–Cole model was used to resolve the components contributing to the loss tangent. Different models of electrical conduction were used to explain the conduction mechanism in the material. The existence of ferroelectricity in the sample was confirmed from the study of the room-temperature P–E loop. The addition of 5% BaSnO3 to BFO resulted in a 10-fold increase in the dielectric constant and the polarization accompanied by reduced tangent loss, making it attractive for device applications.

Ultrathin Free-Standing Nanosheets of Bi2O2Se: Room Temperature Ferroelectricity in Self-Assembled Charged Layered Heterostructure

Ultrathin ferroelectric semiconductors with high charge carrier mobility are much coveted systems for the advancement of various electronic and optoelectronic devices. However, in traditional oxide ferroelectric insulators, the ferroelectric transition temperature decreases drastically with decreasing material thickness and ceases to exist below certain critical thickness owing to depolarizing fields. Herein, we show the emergence of an ordered ferroelectric ground state in ultrathin (∼2 nm) single crystalline nanosheets of Bi2O2Se at room temperature. Free-standing ferroelectric nanosheets, in which oppositely charged alternating layers are self-assembled together by electrostatic interactions, are synthesized by a simple, rapid, and scalable wet chemical procedure at room temperature. The existence of ferroelectricity in Bi2O2Se nanosheets is confirmed by dielectric measurements and piezoresponse force spectroscopy. The spontaneous orthorhombic distortion in the ultrathin nanosheets breaks the local inversion symmetry, thereby resulting in ferroelectricity. The local structural distortion and the formation of spontaneous dipole moment were directly probed by atomic resolution scanning transmission electron microscopy and density functional theory calculations.

Fabrication and impedance spectroscopy of lead free magneto-electric compound: Bi(Ca0.25Ti0.25Fe0.5)O3

Bismuth calcium ferric titanate Bi(Ca0.25Ti0.25Fe0.5)O3 compound is synthesized via solid state reaction route. Using different experimental procedures, the specimen has been characterized. Investigation regarding crystal system with the help of X-ray diffraction (XRD) data suggests the rhombohedral system. Detailed investigations of dielectric and electrical properties of Bi(Ca0.25Ti 0.25Fe0.5)O3 in a broad frequency (1 kHz–1 MHz) and temperature (25–500 °C) ranges have offered a variety of exciting outcomes of conduction mechanism, structure and correlation properties, etc. A significant role of interface in obtaining good dielectric compound has been noticed. The existence of polarization (PE) hysteresis loop indicates the existence of ferroelectricity in the material. The existences of Maxwell–Wagner dielectric relaxation and space charge polarization at low frequencies and high temperatures in the material have been realized. The Nyquist graphs confer the temperature-dependent assistance of grain and grain boundary effect. The transport properties and ac conductivity of the material, which are affected by the temperature and frequency of the applied electric field, have been studied. It exhibits semiconductor behavior. The magneto-electric coupling coefficient of the examined specimen is found to be 3.8 mV cm− 1Oe− 1 at zero magnetic field.

Hydrogen-bonded and supramolecular ferroelectricity in a new hybrid (C12H25NH3)2CoCl4

A new organic-inorganic layered halide perovskite ((C12H25NH3)2CoCl4) has been synthesized and characterized by: chemical analysis, x-ray powder diffraction, differential scanning calorimetry, and differential thermal analysis thermographs. The dielectric and ferroelectric properties have been investigated. Analysis of the ac conductivity σac (ω, T) measured in the temperature interval from 110 K to 370 K and at selected frequencies in the range 1 kHz < f < 100 kHz and the results show that the Jonscher universal power law is accurately obeyed. The existence of ferroelectricity has been demonstrated by the hysteresis P-E loop. The collective data evidenced that the hybrid behaves as a proper ferroelectric rather than a relaxor one and undergoes an order-disorder ferroelectric phase transition at the Curie temperature Tc (Tc ≈ 360 K) accompanied with a structural distortion from an intercalated to non- intercalated state as the other Co and/or Zn hybrids. Since the room temperature space group of the hybrid is centrosymmetric (P21/c), the ferroelectricity should be due to the supramolecular interaction which results from the induced dipoles. The hydrogen bonding system of the type N–H….Cl plays the key role in the mechanism of supramolecular ferroelectricity.

Photoluminescence and optical temperature sensing in Sm3+-doped Ba0.85Ca0.15Ti0.90Zr0.10O3 lead-free ceramics

A series of orange-red emitting Sm3+ activated Ba0.85Ca0.15Ti0.90Zr0.10O3 (BCZT: xSm3+, x = 0.001–0.007) are synthesized by a conventional solid-state reaction method. The Sm3+ ions composition dependent photoluminescence properties are systematically investigated. Under the excitation of a 407 nm near-ultraviolet light, the ceramics exhibit strong characteristic emission of Sm3+ ions with dominant orange-red emission peak at around 595 nm, which is ascribed to the transition of 4G5/2 → 6H7/2. The BCZT: 0.004Sm3+ ceramic displays the optimal emission among these Sm3+-doped BCZT solid solutions. Moreover, the photoluminescence intensity exhibits extremely sensitive to temperature, suggesting that BCZT: 0.004Sm3+ could be applicable for temperature sensing. A maximum relative sensitivity of 1.89% K−1 at 453 K is obtained. Furthermore, the existence of ferroelectricity in the BCZT host combined with Sm3+ activated photoluminescence properties could be useful for developing optical-electro multifunctional materials and devices.

Correlation between polar surface area and bioferroelectricity in DNA and RNA nucleobases.

We have performed computational molecular modelling to study the polarization switching and hysteresis loop behaviours of DNA and RNA nucleobases using the PM3 semi-empirical quantum mechanical approaches. All the nucleobases: adenine (A), thymine (T), guanine (G), cytosine (C), and uracil (U) were modelled. Our study indicates that all the nucleobases exhibit a zero-field polarization due to the presence of polar atoms or molecules such as amidogen and carbonyl. The shape of polarization P versus an applied electric field E hysteresis loop is square, implying typical ferroelectrics behaviour. The total energy U as a function of an applied electric field E exhibits a butterfly-like loop. The presence of zero-field polarization and ferroelectrics hysteresis loop behaviours in nucleobases may support the hypothesis of the existence of bioferroelectricity in DNA and RNA. We also found an interesting relationship between the minimum electric field required for switching [Formula: see text] and the ratio of the topological polar surface area (TPSA) to the total surface area (TSA) of a nucleobase. In particular, the [Formula: see text] of a nucleobase is inversely proportional to the TPSA/TSA ratio. This work may provide useful information for understanding the possible existence of ferroelectricity in biomaterials.