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Erzincan Üniversitesi Erzincan University Fen Bilimleri Enstitüsü Dergisi Journal of Science and Technology 2020, 13(1), 88-94 2020, 13(1), 88-94 ISSN: 1307-9085, e-ISSN: 2149-4584 DOI: 10.18185/erzifbed.673647 Araştırma Makalesi Research Article

Electrical Properties of Ulexite by Dielectric Spectroscopy

Betül CANIMKURBEY 1*

1*S. Şerefeddin Health Services Vocational School, Amasya University, Amasya, 05100, Turkey 2*Central Research Laboratory, Amasya University, 05100, Amasya, Turkey

Geliş / Received: 12/01/2020, Kabul / Accepted: 18/03/2020

Abstract In this work of the material investigation, electrical parameters, which are real part and imaginary part of dielectric constant versus frequency, real part and imaginary part of impedance, dissipation factor, and conductivity, in the bulk ulexite pellet is presented. Electrical properties were investigated dependent temperature and frequency with dielectric spectroscopy. Real and imaginary part of dielectric parameter properties of the ulexite were measured at frequencies from 100 Hz to 15MHz in the temperature range of 25 to 200 ºC. It was observed that AC conductivity increased with increasing frequency at room temperature and decreased with increasing frequency at higher temperatures. Keywords: Ulexite, dielectric spectroscopy, boron, impedance, temperature.

Dielektrik Spektroskopi ile Üleksitin Elektriksel Özellikleri Öz Bu malzeme araştırma çalışmasında, üleksit pelletler için dielektrik sabitinin frekansa karşı reel ve sanal kısmı, empedans, kayıp faktörü, iletkenliğin reel kısmı ve sanal kısmı gibi elektriksel parametreler sunulmuştur. Elektriksel özellikler dielektrik spektroskopi ile sıcaklığa ve frekansa bağlı olarak incelenmiştir. Üleksitin dielektrik parametre özelliklerinin gerçek ve sanal kısımları, 25-200 ºC sıcaklık aralığında 100 Hz-15 MHz frekans aralığında ölçülmüştür. AC iletkenliğin oda sıcaklığında artan frekansla arttığı, daha yüksek sıcaklıklarda ise artan frekansla azaldığı gözlemlenmiştir. Anahtar Kelimeler: Üleksit, dielektrik spektroskopi, bor, empedans, sıcaklık.

1. Introduction boron oxide in different proportions (Yilmaz, 2007). Boron concentrates are either directly Boron is one of the most important materials used in an application area or processed into a used in a wide range of fields such as energy more refined boron product (Mergen & sector, cleaning sector, textile type fiberglass, Demirhan, 2009). Boron compounds such as health and agriculture (Meydan, 2019; D. M. colemanite, tincal and ulexite are attractive Schubert, 2003). Turkey has the world’s materials many application areas due to their largest boron reserves, so Turkey is one of the great properties (Bideci, 2016; Elçiçek & world’s leading producers of boron minerals Kocakerim, 2018). Ulexite which is a mineral- (Anaç & Tamzok, 2007; Kar, Şen, & rich type of boron plays an important role in Demirbaş, 2006). 230 different boron heat and sound insulation, glass, ceramics and minerals are natural compounds containing

*Corresponding Author: [email protected] 88

Electrical Properties of Ulexite by Dielectric Spectroscopy fertilizer industries, boric acid and borax completely sieved in a 45 µm sieve. Following production (Cicek, 2013; D. Schubert, 2000). the material preparation processes, the sample which has 0.5 g weight, was pelletized with a It is seen from the previous studies that boron hydraulic press under a pressure of 10 tons. ore have been used as an alternative radiation The thickness and diameter of the prepared protective material by using with cement or pellets were found to be 1 mm and 12 mm, concrete (Akkurt, Akyildirim, Mavi, respectively. The surface morphology of the Kilincarslan, & Basyigit, 2010; Maslehuddin, sample was analyzed using SEM (Carl Zeiss Naqvi, Ibrahim, & Kalakada, 2013). They 300VP SEM). suggested that concrete containing high percentage of boric acid and concentrated colemanite would be an effective material to protect against ionizing radiation (Aghamiri et al., 2014). Ulexite pellets can be characterized using impedance spectroscopy with the idea that they can be used in many industrial applications that require electrostatic dissipation or electromagnetic shielding (Okutan, Yalçın, et al., 2014).

Characterization by impedance spectroscopy is important due to the possibility of Figure 1. Schematic illustration of ulexite correlating the dielectric properties and the pellet and experimental setup. microstructure of the system (Okutan, Yalçın, et al., 2014). Additionally, materials such as In order to determine the electrical properties concrete, colemanite, ulexite with a high of the ulexite pellets, the ulexite samples imaginer dielectric constant have high energy which were sandwiched between two Ag loss as well as high absorbency (Zhang, electrodes were measured with dielectric Wang, Wei, Guo, & Cao, 2013). spectroscopy method by applying different Characterization by impedance spectroscopy frequencies at different temperatures (Figure can be used to establish structures and defects 1). For this dielectric spectroscopy and understand origin of dielectric losses in measurements, HP 4194A impedance solids. In this study dielectric properties of analyzer was used. It has not been done ulexite which is a boron mineral was annealing process. Temperature dependent investigated by impedance spectroscopy. complex impedance was measured at logarithmic frequencies between 100 Hz and 2. Material and Methods 15 MHz. For temperature control, the NOVOTHERM Temperature Control System The materials used in the study were collected (NTCS) which is enabled for monitoring the from Eti Holding Borax and Acid Factories in temperature in the 25-200 ºC range. The Kütahya, Turkey. Ulexite, which has a crystal structure of ulexite was investigated by specific gravity of 1.95-2 gr/cm3, hardness X-ray diffraction method using Panalytical (mohs) of 2.5 according to the Mohs Hardness Empyrean XRD system. The presence of Scale. Ulexite is boron mineral, which was materials obtained from the X-Ray spectrum crushed and grained by mechanical ways. The by EDX has also been confirmed. ulexite sample had a crushable structure and

Electrical Properties of Ulexite by Dielectric Spectroscopy

3. Results and Discussion

The surface roughness reflected in the was recorded by Carl Zeiss 300VP height of profiles of the images and the scanning electron micrograph. surface distributions of the ulexite pellet

Figure 2. The scanning electron micrograph of the ulexite pellet sample

The scanning electron micrograph of the the ulexite are also presented on figure 2. ulexite sample at magnification of 1,2, 10 SEM images indicate that morphology of µm and 200 nm are shown in figure 2. The ulexite pellet surface has irregular. other parameters of surface morphology of

Figure 3. EDX spectrum of ulexite pellet and data of EDX measurements of sample is given the inset table.

Electrical Properties of Ulexite by Dielectric Spectroscopy

The grains are inhomogeneously distributed The elemental analysis (EDX) spectrum throughout the surface of the sample. ulexite pellet illustrated in figure 3, indicate Micrographs exhibit that the grain size of the the presence of B, C, O, Na, Mg, Si, Ca, in the pellet sample was found to be about 1.5 µm. sample.

Figure 4. XRD patterns of ulexite

The room temperature X-ray diffraction the formation of a ulexite obtained from (XRD) pattern of ulexite (NaCaB509.8H2O) Kestelek boron facilities. Using 2θ, is shown in figure 4. The XRD pattern (i.e., interplaner spacing (d) of each peak was peak position and intensity) clearly shows obtained.

Figure 5. Variation of the (a) real (ɛʹ) and (b) imaginary (ɛʹʹ) part of complex dielectric constant as a function of frequency at different temperature for ulexite.

Electrical Properties of Ulexite by Dielectric Spectroscopy

Variation of the real (ɛʹ) (Fig. 5a) and and the presence of temperature dispersion imaginer (ɛʹʹ) (Fig. 5a) part of dielectric and the tangent loss supports the constant as a function of frequency at phenomena of diffuse phase transition different temperature for ulexite. Dielectric (Okutan, Kavanoz, et al., 2014). relaxation peak indicates a phase transition

Figure 6. (a) The Cole- Cole plots of the ulexite pellet (b) shows loss tangent (δ) as a function of frequency at room temperature for ulexite.

The Cole- Cole plots of the ulexite pellet align with the applied alternating electric was shown in figure 6 (a). Figure 6(b) field but as frequency increases diploes shows loss tangent (δ) as a function of cannot cope up with the pace of fast frequency at room temperature for ulexite. changing electric field and therefore This behavior occurs because, at low dielectric constant decreases and become frequencies, dipoles easily respond and saturated at further higher frequencies.

Figure 7. AC Conductivity versus frequency dependent temperature for ulexite pellet

Electrical Properties of Ulexite by Dielectric Spectroscopy

But in this work, there is anomalies. dielectric parameter properties of the Dielectric constant values have increased ulexite were measured at frequencies from with increased frequency. While the real 100 Hz to 15MHz in the temperature range part of the dielectric permittivity (ɛ′) has the of 25 to 200 °C. It was observed that AC same values because of no charge conductivity increased with increasing accumulation at the interface, which can be frequency at room temperature and AC explained by the ion diffusion mechanism at conductivity decreased with increasing higher frequencies; the charges get frequency at higher temperatures for accumulated at the interfacial region at ulexite. Additionally, the dielectric losses lower frequencies (Bazan, Duffy, Ingram, & have increased with increasing frequency. Mallace, 1996; Sidebottom, Green, & This increase is more rapid in the dispersion Brow, 1995). Additionally, AC region. At higher frequency, dielectric Conductivity versus frequency dependent constant has increased to 150 ºC and then temperature for ulexite pellet was shown in began to decline. Anomalies, near 170, 190 figure 7. and 200 ºC which are particularly well seen in the temperature dependence of (Fig. 5). 4. Conclusion The temperatures 30 ºC are close to the temperatures of anomalies in water (ice– In this paper, an effort has been made to water first-order phase transition and determine the dielectric properties of anomalies in the compressibility and heat ulexite. Dielectric properties of ulexite capacity of water (Gavrilova, Lotonov, & which is boron mineral was investigated by Kornilova, 2008). The likely reason for impedance spectroscopy. Electrical this is that the structure of ulexite contains properties were investigated dependent hydrogen bonds, the same as in the structure temperature and frequency with dielectric of water. spectroscopy. Real and imaginary part of

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Electrical Properties of Ulexite by Dielectric Spectroscopy

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