RINP 534 No of Pages 9, Model 5G 11 January 2017 Results in Physics xxx (2017) xxx–xxx Contents lists available at ScienceDirect Results in Physics journal homepage: www.journals.elsevier.com/results-in-physics Optical basicity and electronic polarizability of zinc borotellurite glass doped La3+ ions M.K Halimah ⇑, M.F Faznny, M.N Azlan, H.A.A Sidek Physics Department, Faculty of Science, Universiti Putra Malaysia (UPM), 43400 Serdang, Selangor, Malaysia a r t i c l e 12 13 14 15 16 17 18 19 20 21 22 23 24 i n f o Article history: Received 18 October 2016 Received in revised form January 2017 Accepted January 2017 Available online xxxx Keywords: Borotellurite glasses Refractive index Electronic polarizability Oxide ion polarizability Optical basicity Metallization criterion a b s t r a c t Zinc borotellurite glasses doped with lanthanum oxide were successfully prepared through meltquenching technique The amorphous nature of the glass system was validated by the presence of a broad hump in the XRD result The refractive index of the prepared glass samples was calculated by using the equation proposed by Dimitrov and Sakka The theoretical value of molar refraction, electronic polarizability, oxide ion polarizability and metallization criterion were calculated by using Lorentz-Lorenz equation Meanwhile, expression proposed by Duffy and Ingram for the theoretical value of optical basicity of multi-component glasses were applied to obtain energy band gap based optical basicity and refractive index based optical basicity The optical basicity of prepared glasses decreased with the increasing concentration of lanthanum oxide Metallization criterion on the basis of refractive index showed an increasing trend while energy band gap based metallization criterion showed a decreasing trend The small metallization criterion values of the glass samples represent that the width of the conduction band becomes larger which increase the tendency for metallization of the glasses The results obtained indicates that the fabricated glasses have high potential to be applied on optical limiting devices in photonic field Ó 2017 Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/) 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 Introduction 45 Lately, TeO2 based glasses have attracted much attention to be applied as a nonlinear optical material with excellent optical properties because it possess high linear refractive value of more than and good infrared transmittance [1] Thus, TeO2 glasses have been suggested to be applied in photonic devices B2O3 is chosen to be added due to its low melting point and good rare-earth ions solubility [2] meanwhile ZnO is added into the glass composition because ZnO can helps to improve the glass forming ability and lowers the crystallization rates of borotellurite glass network [3] Lanthanum is selected to be doped into the glass in order to determine the influence of lanthanum which is the only element in the rare earth group without any f shell electron to borotellurite glass system Photonics based system or devices that uses photons for information and image processing is labeled as one of the technologies of the 21st century, in which nonlinear optical process provide the key functions of frequency conversion and optical switching [4] 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 ⇑ Corresponding author E-mail addresses: halimahmk@upm.edu.my (M.K Halimah), faznnymf@gmail com (M.F Faznny), azlan_wildan@yahoo.com (M.N Azlan), sidek@upm.edu.my (H.A.A Sidek) Since optical nonlinearity is greatly influenced by electronic polarizability of a material upon exposure to intense light beam, it is very important to determine the intrinsic relationship between electrical polarizability and optical nonlinearity in materials Electronic polarizability is closely related to many properties of a material such as refraction, conductivity, ferroelectricity, electrooptical effect, optical basicity and optical nonlinearity [5] In 2005, polarizability approach based on Lorentz-Lorenz equations of many oxide glasses had been investigated by Dimitrov and Komatsu Polarizability approach based on the Lorentz-Lorenz equations is an estimation of the state of polarization of ions of an oxide or glass system Dimitrov and Komatsu then manage to calculate the oxide ion polarizability, optical basicity and metallization criterion on the basis of two different properties: energy band gap and linear refractive index On the other hand, optical basicity that is strongly influenced by electronic polarizability has been proven to be a crucial and essential parameter for predicting properties of a glass system before applying the glass in various applications [6] Recently, researches on TeO2 based glasses have been focused on discovering and determining the linear optical properties of glasses of various compositions Hence, it is strongly recommended to further the research on the electronic polarizability, optical http://dx.doi.org/10.1016/j.rinp.2017.01.014 2211-3797/Ó 2017 Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Please cite this article in press as: Halimah MK et al Optical basicity and electronic polarizability of zinc borotellurite glass doped La3+ ions Results Phys (2017), http://dx.doi.org/10.1016/j.rinp.2017.01.014 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 RINP 534 No of Pages 9, Model 5G 11 January 2017 85 86 87 88 89 90 91 92 93 M.K Halimah et al / Results in Physics xxx (2017) xxx–xxx basicity and metallization criterion to predict the nonlinear optical properties of the materials The purpose of this research is to prepare zinc borotellurite glass doped with various concentrations of lanthanum oxide and to utilize the polarizability approach developed by Dimitrov and Sakka that is by using experimental data for optical band gap in order to the calculate the polarizability, optical basicity and metallization criterion of the glass sample theoretically Experimental 3+ 124 The La doped zinc borotellurite glass system {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x where x = 0.01, 0.02, 0.03, 0.04, and 0.05 M fraction were fabricated through melt-quenching technique By using a digital weighing machine with an accuracy of ± 0.0001 g, reagent grade of boron oxide, B2O3 (98.5%, Alfa Aesar), zinc oxide, ZnO (99.99%, Alfa Aesar), tellurium (IV) oxide, TeO2 (99.99%, Alfa Aesar) and lanthanum (III) oxide, La2O3, (99.99%, Alfa Aesar) were weighted at appropriate amount and transferred into an alumina crucible The weighted chemicals were stirred for 30 to obtain homogeneity and transferred to the first electric furnace for preheat process at 400 °C for h Next, the chemicals were melted for h at 900 °C in the second electrical furnace while the stainless steel mould was preheated in the first furnace After h, the molten was quickly poured into preheated stainless steel mould The melts undergoes annealing process in the first electric furnace for h at 400 °C to eliminate air bubbles in the glass and to diminish thermal strains or stress The glass was left to be cooled to room temperature before cutting, grinding and polishing procedure For optical measurement, the fabricated glass was cut to a thickness approximate to mm and polished both sides using silicon carbide paper with different grid to acquire flat and parallel surface The sample was sent to be characterized by using UV1650PC UV–Vis Spectrophotometer (Shimadzu) with the wavelength range from 220 to 2600 nm to obtain the optical absorption For structural characterization, the prepared glass sample was crushed by using a plunger and grinded using pestle and mortar in order to acquire fine powder The powder form glass sample was sent to X-ray Diffraction (XRD) and Fourier Transform InfraRed Spectroscopy (FTIR) to investigate the structure of the glass sample 125 Result and discussion 126 X-ray diffraction (XRD) 127 134 XRD has been vastly used to determine the crystallinity and structure of a material The X-ray diffraction spectrum of prepared glass samples were shown in Fig The absences of sharp peaks in the XRD pattern implied that the prepared glass sample not possess long range periodic lattice arrangement of a crystal A broad hump that was observed in the XRD pattern validate that the sample is not a crystal, noncrystalline and is amorphous in nature [7] 135 Fourier transform infrared spectroscopy (FTIR) 136 FTIR is a nondestructive technique that capable of providing thorough information about the structure of local arrangement in glass system In a glass system, molecules that form bonds or group will absorb specific frequencies to rotate and vibrates when the glass samples undergoes infrared spectroscopy The FTIR spectra of the prepared glass sample are presented in Fig while the peak positions and assignment are listed in Table 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 128 129 130 131 132 133 137 138 139 140 141 142 It can be seen from Fig that the transmission spectra of the glass samples consist of two broad absorption bands at 631– 645 cmÀ1 and 1239–1243 cmÀ1 There is also a small absorption band positioned in the range of 950–1050 cmÀ1 for glass sample that contain 0.05 M fraction of lanthanum oxide The absorption band at 600–700 cmÀ1 is assigned to stretching vibration of Te–O bonds that consist of trigonal bipyramid, TeO4 which in the range of 600–650 cmÀ1 and trigonal pyramid, TeO3 which assigned in between 650 and 700 cmÀ1 Thus, the decrease in intensity peak in the range of 631–645 cmÀ1 might be due to the existence of TeO4 group in all tellurite containing glass system [8] The absorption band for pure borate glass, B2O3 is assigned in the range of 806 cmÀ1 which indicates the characteristic of boroxyl ring The absorption band of boroxyl ring vanishes while the absorptions band for BO3 and BO4 structural units appears after the glass formation This indicates that BO3 and BO4 exist after the glass formation process as a result of the replacement of boroxyl ring [9] The absorption spectra for B-O bond can be divided into regions: 800–1200 cmÀ1 that indicate B-O stretching of tetrahedral BO4 units and B-O stretching of trigonal BO3 units that was assigned to 1200–1800 cmÀ1 in the FTIR spectra [10] From the FTIR spectra, a wide absorption band positioned at 1239– 1243 cmÀ1 that is attributed to the trigonal B–O bond stretching vibrations of BO3 units was recorded in all glass samples while a small absorption band at $975 cmÀ1 was detected in only 0.05 M fraction of lanthanum oxide that indicates tetrahedral B-O bond stretching vibrations of BO4 units present in the glass system 143 Density 171 Density of a glass is one of the important physical property that able to evaluate the compactness in the structure of the glass system In this research, density measurement was determined at room temperature by applying Archimedes principle where the samples were immersed in distilled water Density values that were tabulated in Table shows an increasing trend as concentration of lanthanum increases The rise in density value might contributed by the replacement of lower atomic mass glass former, Te with high atomic mass dopant, La [11] 172 Optical absorption, energy band gap, urbach energy 181 Optical absorption and the optical absorption edge are very important in order to investigate optically induced transitions and to get information about the band structure and energy gap of a non-crystalline material [12] The optical absorption spectra for {[(TeO2)0.70(B2O3)0.30]0.7 (ZnO)0.3}1Àx (La2O3)x glasses was presented in Fig From the optical absorption spectra, there are no sharp peaks to be seen The absence of sharp peaks in the optical absorption spectra corresponds to characteristic of materials that is amorphous in nature [13] As the amount of lanthanum oxide added into the glass system increases, it can be observed that the fundamental absorption shifts to lower wavelength This occurs due to the increase in rigidity of the glass system as content of lanthanum oxide increases [14] By using the absorbance value obtained from UV–Vis spectroscopy, the optical absorption coefficient, a(w) can be calculated by applying the equation: 182 awị ẳ 2:303A=dị ð1Þ where d represents the thickness of the glass samples in cm and A is the absorbance Relationship between absorption coefficients with photon energy has been proposed by Mott and Davis to calculate direct and indirect transition occurred in the band gap [15] Please cite this article in press as: Halimah MK et al Optical basicity and electronic polarizability of zinc borotellurite glass doped La (2017), http://dx.doi.org/10.1016/j.rinp.2017.01.014 3+ ions Results Phys 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 173 174 175 176 177 178 179 180 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 200 201 202 203 204 205 RINP 534 No of Pages 9, Model 5G 11 January 2017 M.K Halimah et al / Results in Physics xxx (2017) xxx–xxx 0.01 La 1800 0.02 La Counts 1600 0.03 La 1400 0.04 La 1200 0.05 La 1000 800 600 400 200 20 30 40 50 60 70 80 Position, 2θ (°) Fig X-ray diffraction patterns of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses Trnasmittance (%) 100 80 60 0.01 La 0.02 La 0.03 La 0.04 La 0.05 La 40 20 200 400 600 800 1000 1200 1400 1600 1800 2000 Wavenumber (cm-1) Fig FTIR spectra of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses Table Assignment of infrared transmission bands for {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses No 0.01 0.02 0.03 0.04 0.05 Assignments 1239 – 631 1241 – 637 1239 – 639 1241 – 645 1243 975 640 Trigonal B-O bond stretching vibrations of BO3 units from boroxyl groups [9] B-O bond stretching vibrations in BO4 tetrahedral from tri-, tetra-, and penta – borate groups [10] TeO4 group exist in all tellurite containing glass [8] The plot of direct and indirect band gap of the glass samples are presented in Fig and Fig respectively while the values of the direct and indirect band gap are tabulated in Table and plotted in Fig Urbach energy (4E) that represents a measure of disorder in materials can be estimated by using the equation Table Density of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses 206 208 209 210 211 212 La molar fraction, x Density (g/cm3) 0.01 0.02 0.03 0.04 0.05 3.54 3.63 4.74 5.97 6.64 aðwÞ ¼ ðBðhx À Eopt Þn Þ=ðhxÞ aðwÞ ¼ b expðhx=DEÞ ð2Þ where B is an energy-independent constant called band tailing parameter, hx is photon energy and n is a constant that determine the type of optical transition Values for n are and ½ for indirect and direct forbidden transition respectively [16] ð3Þ where b is a constant, h is the plank constant, w is the photon frequency and 4E is the Urbach energy [17] Urbach energy is calculated by taking reciprocal of the slopes of linear portion from the graph of ln a versus hx The values of the Urbach energy are tabulated in Table and plotted in Fig Both direct and indirect optical band gap in Fig show an increasing trend as amount of lanthanum oxide in the glass system increases Optical band gap for both direct and indirect depend on Please cite this article in press as: Halimah MK et al Optical basicity and electronic polarizability of zinc borotellurite glass doped La (2017), http://dx.doi.org/10.1016/j.rinp.2017.01.014 3+ ions Results Phys 213 214 215 216 217 218 219 221 222 223 224 225 226 227 228 229 RINP 534 No of Pages 9, Model 5G 11 January 2017 M.K Halimah et al / Results in Physics xxx (2017) xxx–xxx Absorbance 0.8 0.7 0.01 La 0.6 0.02 La 0.03 La 0.5 0.04 La 0.4 0.05 La 0.3 0.2 0.1 0.0 200 300 400 500 600 700 800 Wavelength, λ (nm) Fig Optical absorbance spectra of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1x (La2O3)x glasses ()ẵ (cm-ạ eV)ẵ 18 16 0.01 La 14 0.02 La 0.03 La 12 0.04 La 10 0.05 La 2.0 2.5 3.0 3.5 4.0 4.5 Photon energy, ћѡ (eV) Fig Plot of versus photon energy, ⁄x of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses for indirect band gap measurement 100 0.01 La 0.02 La 0.03 La 0.04 La 0.05 La (αћѡ)² (cm-¹ eV)² 90 80 70 60 50 40 30 20 10 2.0 2.5 3.0 3.5 4.0 4.5 Photon energy, ћѡ (eV) Fig Plot of ða hxÞ versus photon energy, ⁄x of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses for direct band gap measurement Please cite this article in press as: Halimah MK et al Optical basicity and electronic polarizability of zinc borotellurite glass doped La3+ ions Results Phys (2017), http://dx.doi.org/10.1016/j.rinp.2017.01.014 RINP 534 No of Pages 9, Model 5G 11 January 2017 M.K Halimah et al / Results in Physics xxx (2017) xxx–xxx Table Indirect optical band gap (E1opt), Direct optical band gap (E2opt) and Urbach energy of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses La molar fraction, x Indirect Band Gap, E1opt, (eV) Direct band gap, E2opt (eV) Urbach energy, 4E (eV) 0.01 0.02 0.03 0.04 0.05 2.20 2.49 2.60 2.61 3.43 2.20 3.10 3.20 3.30 3.90 0.47 0.45 0.42 0.41 0.33 241 242 Refractive index 243 Refractive index value of a glass is influenced by the interaction of light with the electrons of the constituent atoms of the glass [20] The refractive index value of fabricated glass samples are calculated using 231 232 233 234 235 236 237 238 239 240 244 245 246 247 250 251 252 253 254 255 256 257 258 259 n2 1ị=n2 ỵ 2ị ẳ q Eopt =20 ð4Þ where n is the refractive index and Eopt is the value of indirect band gap [21] The values of the refractive index that are tabulated in Table shows a decreasing trend The decrement in refractive index might be due to the incorporation of modifier that attributed to the decrease in the number of nonbridging oxygens [22] Thus, the decreasing value of refractive index as amount of lanthanum oxide increases is due to the decreasing number of high polarizability nonbridging oxygen Refractive index of the fabricated glasses are higher when compared to previous research that obtained the refractive index values in the range of 1.70–1.74 by Azlan et al Molar refraction is a measure of the total polarizability of a mole of a material Through Lorentz-Lorenz equation, the relationship between molar refraction, Rm to refractive index, no and molar volume, Vm for isotropic substance such as liquid, glasses and cubic crystals can be identified [23] 261 ½ðn20 À 1ị=n20 ỵ 2ịVm 5ị where Rm is the molar refraction, Vm is the molar volume and n0 is the refractive index Electronic polarizability is the magnitude of electrons responds to an electric field which can be calculated by applying following equation: am ẳ 3=4pNA ịịRm 6ị where am stands for electronic polarizability, NA represent the Avogadro’s number With am in (Å3), Eq (6) is transformed to the following expression am ¼ Rm =2:52 ð7Þ Calculation of the oxide ion polarizability, aOÀ2 on the basis of two independent initial values that is linear refractive index, n and energy band gap, Eg was originally proposed by Dimitrov and Sakka for simple oxide, but extended to various binary glasses by Vithal et al [25] and Dimitrov and Komatsu [26] aO2 nị ẳ ẵRm =2:52ị Rai NO2 ị1 aO2 Eg ị ẳ ẵVm =2:52Þð1 À qffiffiffiffiffiffiffiffiffiffiffiffiffi Eg =20Þ À Rai ðNỒ2 ÞÀ1 ð8Þ 266 268 269 270 271 272 273 274 276 277 278 279 280 281 283 2.8 2.8 2.4 2.4 2.0 2.0 0.04 0.05 285 286 287 288 289 290 291 292 294 295 296 297 298 299 301 302 ð9Þ Indirect band gap, E1opt (eV) 3.2 0.03 265 293 3.2 0.02 264 Oxide ion polarizability 3.6 0.01 263 284 3.6 262 The calculated values for molar refraction and electronic polarizability are shown in Table and are plotted in Fig Both of the decreasing trend occurred due to the decreasing number of nonbridging oxygen in the glass system as concentration of La2O3 increases Nonbridging oxygen have high tendency to polarize compared with bridging oxygen [24] Since the amount of bridging oxygen that has a low polarizability is more than amount of nonbridging oxygen that has high polarizability, the glasses fabricated tend to be less polarized 4.0 Direct band gap, E2opt (eV) 249 260 Rm ¼ the changes in the structure of glass after the addition of modifier [18] The decreasing number of non-bridging oxygen is one of the reasons that contribute to an increment in energy band gap values [9] The number of non-bridging oxygen decreases because of the increasing number of oxygen anions such as TeO4 that are tightly bound to the host materials It was shown in Fig that the Urbach energy decreases with increase of La2O3 content The low Urbach energy is related to the decrease of degree of disorderness in glass structure [19] In this case, as the concentration of the lanthanum ion increases, fragility and Urbach energy decreases due to the decreasing number of nonbridging oxygen and BO3 units in the glass system 230 Molar refraction and electronic polarizability 0.06 La molar fraction, x Fig Direct and indirect energy band gap of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses Please cite this article in press as: Halimah MK et al Optical basicity and electronic polarizability of zinc borotellurite glass doped La3+ ions Results Phys (2017), http://dx.doi.org/10.1016/j.rinp.2017.01.014 304 RINP 534 No of Pages 9, Model 5G 11 January 2017 M.K Halimah et al / Results in Physics xxx (2017) xxx–xxx Urbach energy(△E) 0.50 0.46 0.42 0.38 0.34 0.30 0.00 0.01 0.02 0.03 La molar fraction, x 0.04 0.05 0.06 Fig Urbach energy of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses can be obtained The molar cation polarizability values of Te4+, B+, Zn3+ and La3+ ions are respectively aTe = 1.595 Å3, aB = 0.0002 Å3, aZn = 0.283 Å3 and aLa = 1.052 Å3 The calculated values of aỒ2 ðnÞ and aỒ2 ðEg Þ are tabulated in Table while the graph of oxide ion polarizability versus molar fraction of La2O3 is plotted in Fig The values of both refractive index and energy band gap based oxide ion polarizability have the same decreasing trend The decreasing trend occurs due to decreasing amount of nonbridging oxygen that has high polarizability as concentration of lanthanum oxide increases in the glass system The decreasing in nonbridging oxygen number can be proven in the FTIR result where the fraction of TeO3 structural units with nonbridging oxygen decreases while the fraction of TeO4 structural units with bridging oxygen increases It can be clearly seen that the value of aỒ2 ðEg Þ is slightly larger than aỒ2 ðnÞ The differences between values of aỒ2 ðEg Þ and aỒ2 ðnÞ can be explained by the existence of the localized density states in band gap energy based from the theory of conduction in non-crystalline [28] Table Refractive index of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses La molar fraction, x Refractive index, n 0.01 0.02 0.03 0.04 0.05 2.50 2.31 2.30 2.29 2.19 Table Molar refraction and polarizability of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses 306 307 308 309 310 311 312 La molar fraction, x Molar refraction, (cm ) Electronic Polarizability (10À25) 0.01 0.02 0.03 0.04 0.05 21.43 19.79 15.34 12.31 10.73 8.50 7.86 6.09 4.89 4.26 Table Oxe ion polarizability of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses where aỒ2 ðnÞ stand for refractive index based oxide ion electronic polarizability, aOÀ2 ðEg Þ is energy band gap based oxide ion polarizability, Rai represent molar cation polarizability and NOÀ2 denotes the number of oxide ions in the chemical formula The values of Ra1 are given by x1kaA + x2maB + x3naC + x4oaD while NOÀ2 is given by x1i + x2k + x3l + x4m [27] From Dimitrov and Komatsu data of molar cation polarizability [28], the molar cation polarizability values of every element in the glass system La molar fraction, x Refractive index based oxide ion electronic polarizability, aỒ2 ðnÞ Energy band gap based oxide ion electronic polarizability, aỒ2 ðEg Þ 0.01 0.02 0.03 0.04 0.05 3.97 3.60 2.67 2.03 1.70 4.19 3.99 2.94 2.26 1.80 24 20 16 12 Molar Refraction Electronic Polarizability 305 0.00 0.01 0.02 0.03 0.04 0.05 0.06 La molar fraction, x Fig Molar refraction and electronic polarizability of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.3}1Àx (La2O3)x glasses Please cite this article in press as: Halimah MK et al Optical basicity and electronic polarizability of zinc borotellurite glass doped La3+ ions Results Phys (2017), http://dx.doi.org/10.1016/j.rinp.2017.01.014 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 RINP 534 No of Pages 9, Model 5G 11 January 2017 5 4 3 2 1 0.01 0.02 0.03 0.04 0.05 0.06 La molar fraction, x Energy band gap based oxide ion polarizability Refractive index based oxide ion polarizability M.K Halimah et al / Results in Physics xxx (2017) xxx–xxx Fig Oxide ion polarizability of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses Table Optical basicity of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses Table Metallization criterion of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses La molar fraction, x Theoretical optical basicity, Kth Refractive index based oxide ion optical basicity, K (n) Energy band gap based optical basicity, K (Eg) 0.01 0.02 0.03 0.04 0.05 0.8934 0.8982 0.9029 0.9075 0.9117 1.25 1.21 1.04 0.85 0.68 1.27 1.25 1.10 0.93 0.74 332 Optical basicity 333 340 The electron donating power of the oxygen in a glass system that controls the effectiveness of cation hosting sites for photonic applications like in host materials for lasers can be quantified using theoretical optical basicity [30] Optical basicity is also a measure of the acid-base properties of oxides, glasses, alloys, slags and molten salts Theoretical optical basicity, Kth for multi-component glasses can be determined according to an approach proposed by Duffy and Ingram: 341 343 Kth ¼ X1K1 ỵ X2K2 ỵ X3K3 ỵ ỵ XnKn 335 336 337 338 339 344 345 ð10Þ where X1, X2, X3, ., Xn represents the equivalent fractions of each oxides in which contributes to the overall material stoichiometry Refractive index based metallization criterion, M(no) Energy band gap based metallization criterion, M(Eg) 0.01 0.02 0.03 0.04 0.05 0.3636 0.4089 0.4115 0.4141 0.4414 0.0224 0.0316 0.0387 0.0447 0.0500 and K1, K2, K3, ., Kn stands for optical basicity of each individual oxides in the glass system [24] The optical basicity of each oxide are K(TeO2) = 0.93, K(B2O3) = 0.43, K(ZnO) = 1.03 and K(La2O3) = 1.07 [31] The theoretical optical basicity values were listed in Table Duffy has established an alternative approach of optical basicity that can be obtained from the oxide ion polarizability data on the basis of linear refractive index, n and energy band gap, Eg [32] K ẳ 1:67ẵ1 1=aO2 ị 11ị The obtained values of optical basicity are shown in Fig 10 and Table It can be clearly seen that the optical basicity on the basis of n and Eg decreases as content lanthanum oxide increases The decreasing trend in both optical basicity values indicates that the glasses prepared are acidic in nature Decreasing optical basicity values is because of the decreasing negative charge on the oxygen 1.4 1.4 1.3 1.3 1.2 1.2 1.1 1.1 1.0 1.0 0.9 0.9 0.8 0.8 0.7 0.7 0.6 Energy band gap based optical basicity Refractive index based optical basicity 334 La molar fraction, x 0.6 0.01 0.02 0.03 0.04 0.05 0.06 La molar fraction, x Fig 10 Optical basicity of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses Please cite this article in press as: Halimah MK et al Optical basicity and electronic polarizability of zinc borotellurite glass doped La3+ ions Results Phys (2017), http://dx.doi.org/10.1016/j.rinp.2017.01.014 346 347 348 349 350 351 352 353 355 356 357 358 359 360 361 RINP 534 No of Pages 9, Model 5G 11 January 2017 M.K Halimah et al / Results in Physics xxx (2017) xxx–xxx 0.46 0.42 0.44 0.40 0.42 0.38 0.40 0.36 0.38 0.34 Energy band gap based metallization criterion Refractive index based metallization criterion 0.32 0.36 0.01 0.02 0.03 0.04 0.05 0.06 La molar fraction, x Fig 11 Refractive index and energy band gap based metallization criterion of {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.3}1Àx (La2O3)x glasses 362 363 364 365 366 367 368 369 370 371 372 atoms that lead to decreasing covalency in the cation-oxygen bonding [29] The experimental optical basicity value was found to be different from the theoretical optical basicity value, Kth According to Duffy and Ingram in 1992 [33], the principle behind Eq (10) was to predict the trends in optical basicity rather than giving and revealing the ’true’ optical basicity value Although agreement between Kth and experimental basicity value in many glass system is fairly good, the values were seldom be exactly the same The disagreement between Kth and experimental basicity value might occurs as a result of significant structural changes such as change in coordination number [33] 373 Metallization criterion 374 384 Metallization criterion is theoretically calculated to determine the tendency for metallization and to investigate the insulating behavior of the fabricated glasses Herzfeld [34] has proposed the theory on metallization of the condensed matter that explained that the refractive index become infinite for the condition Rm/ Vm = in the Lorentz-Lorenz equation Materials with the condition Rm/Vm = or Rm/Vm > have mobile electron and the system of the materials are predicted to be metallic in nature while materials with the condition Rm/Vm < are predicted to have nonmetallic nature [23,27] Subtracting by gives the metallization criterion, M: 385 387 M ẳ Rm =Vm ị 375 376 377 378 379 380 381 382 383 ð12Þ 390 Metallization criterion on the basis of refractive index, M(n0) and energy band gap, M(Eg) have been calculated by Dimitrov and Sakka by using the following expression [35]: 391 393 Mn0 ị ẳ ẵn20 1ị=n20 ỵ 2ị 388 389 394 396 397 398 399 400 401 402 403 404 405 406 407 MEg ị ẳ q Eg =20 13ị 14ị M(n0) and M(Eg) values for {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses that are calculated using Eqs (3.13) and (3.14) are shown in Table and are plotted as a function of La2O3 concentration in Fig 11 Both the refractive index based and energy band gap based metallization criterion increases with increasing La2O3 amount indicates that the tendency for metallization in the electronic structure is low in the fabricated glasses with high La2O3 content The increasing trend in metallization criterion on the basis of band gap energy indicates that the samples are not metalizing and the width of conduction bands becomes smaller [36] Conclusion 408 Oxide ion polarizability, optical basicity and metallization criterion based on refractive index and energy band gap have been calculated theoretically for {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.3}1Àx (La2O3)x 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Results Phys (2017), http://dx.doi.org/10.1016/j.rinp.2017.01.014 ... {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses Please cite this article in press as: Halimah MK et al Optical basicity and electronic polarizability of zinc borotellurite glass doped La3+ ions Results Phys (2017),... {[(TeO2)0.70(B2O3)0.30]0.7(ZnO)0.30}1Àx (La2O3)x glasses Please cite this article in press as: Halimah MK et al Optical basicity and electronic polarizability of zinc borotellurite glass doped La3+ ions Results Phys (2017),... Please cite this article in press as: Halimah MK et al Optical basicity and electronic polarizability of zinc borotellurite glass doped La3+ ions Results Phys (2017), http://dx.doi.org/10.1016/j.rinp.2017.01.014