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Detection of rhombo-ortho-tetra-cubic phase transitions on poled Er3+ and Sn4+ doped BaTiO3 ceramics by up-conversion luminescence
Journal Pre-proofs Detection of rhombo-ortho-tetra-cubic phase transitions on poled Er3+ and Sn4+ doped BaTiO3 ceramics by up-conversion luminescence Mohd Azaj Ansari, K. Sreenivas PII: DOI: Reference:
S0167-577X(19)31926-3 https://doi.org/10.1016/j.matlet.2019.127294 MLBLUE 127294
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
30 October 2019 24 December 2019 31 December 2019
Please cite this article as: M.A. Ansari, K. Sreenivas, Detection of rhombo-ortho-tetra-cubic phase transitions on poled Er3+ and Sn4+ doped BaTiO3 ceramics by up-conversion luminescence, Materials Letters (2019), doi: https:// doi.org/10.1016/j.matlet.2019.127294
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier B.V.
Detection of rhombo-ortho-tetra-cubic phase transitions on poled Er3+ and Sn4+ doped BaTiO3 ceramics by up-conversion luminescence
Mohd Azaj Ansaria,*and K. Sreenivasa,* a
Department of Physics & Astrophysics, University of Delhi, Delhi-110007, India
Abstract The three ferroelectric phase transitions rhombohedral-orthorhombic-tetragonal-cubic in 0.5 mole% Er doped BaSn0.06Ti0.94O3 ceramics are detected through up-conversion luminescence measurements. Noticeable changes are observed at the phase transition temperatures in the up-converted emission line intensity at 524 nm and the integrated intensity of the green emission band (514-537 nm) under 980 nm excitation. An electrically poled surface is found to be more sensitive, and the observed phase transition temperatures by the luminescence method are in agreement with the heat capacity and dielectric phase transition temperatures.
Keywords:
Ceramics; Ferroelectrics; Luminescence; Phase transformations
*Corresponding author. Tel.: +91 9810958703, +91 8447038918 E-mail address:
[email protected] (Mohd. Azaj Ansari) [email protected] (K. Sreenivas),
1
1. Introduction Up-conversion photoluminescence (UCPL) measurements have attracted a lot of interest as a new spectroscopic tool to study ferroelectric phase transitions by the non-contact mode [1,2]. Luminescence measurements are found to be sensitive to composition induced changes in lattice symmetry, site selectivity of RE ions, polarization, and temperature induced phase transitions [3,4,5,6]. More recently, interesting revelations through variations in UCPL intensity due to changes in ferroelectric order [1], electrical poling [7], field induced enhancement and modulation in Er/Yb doped BaTiO3 thin films have been reported. [8]. However, studies on different ferroelectric materials for the detection of structural phase transition, the reported literature presents contrasting results. For example: (i) measurements on Er3+ doped (Ba0.97Ca0.03Sn0.06Ti0.94)O3 revealed a broad transition over a wide temperature range (75-550K) [9], (ii) studies on K0.5Na0.5NbO3 ceramic revealed opposite variations in the emission intensity (increasing/decreasing) for the two phase transitions exhibited by K0.5Na0.5NbO3 [10]. Zuo et al. [11] have emphasized that UCPL intensity ratio is more effectual than the changes in emission line intensity.
Sn4+ is known to substitute
preferentially for Ti4+, and decreases the tetragonal-to-cubic (TT-C) phase transition temperature in comparison to undoped BaTiO3 as reported earlier [12]. However, Er3+ with intermediate size can substitute for either/both the cation sites (Ba2+ or Ti4+) with oxygen vacancies. A preferential substitution of Er3+ for Ba2+ has been reported for Ba/Ti<1 upto 2-5 at. %. [2, 13]. The present study is focused on 0.5 mole% Er doped BaSn0.06Ti0.94O3 (5ErBSn6T). A poled ceramic surface is shown to be more effective for the detection of all the three successive structural phase transitions exhibited by Er3+ modified BaSn0.06Ti0.94O3 using the luminescence method. The measured phase transition temperatures are compared with other techniques.
2
2. Materials and methods Ba1-y Ery Sn0.06Ti0.94O3 ceramic compositions with varying Er content (y mole % = 0, 0.1, 0.3, 0.4, 0.5, 0.6, and 0.9, abbreviated as (0Er-BSn6T…...9Er-BSn6T), were prepared by solid-state reaction. High purity Er2O3, BaCO3, TiO2 and SnO2 powders were calcined at 1200° C for 3h, pressed into 1mm thick 10 mm diameter ceramic discs, and sintered at 1350°C for 5h. Novocontrol impedance analyzer, and a modulated differential scanning calorimeter (MDSC) were used for dielectric and heat capacity measurements respectively. For optical measurements, the ceramic was mechanically thinned (0.4mm), polished and reannealed at 1200° C for 2h. Air drying silver paint was used for electroding the ceramics to pole them under a DC field of 12kV/mm for 30 minutes, and later carry out the dielectric measurements at a fixed frequency of 1MHz with 1V perturbing voltage amplitude. For the optical measurements the air drying silver paint was removed gently with acetone. Upconversion luminescence spectra were recorded at 2°C temperature interval using a Quanta master -8450-11 (Horiba) spectrofluorometer, equipped with a cooled detector under 980 nm excitation (laser power 400 mW). 3. Results and Discussion Light upconversion luminescence at room temperature in the prepared Er3+ doped BaSn0.06Ti0.94O3 samples is shown in Fig.1. The observed green emission bands (Ig1: 514-537) and (Ig2: 540-575 nm), and the weak red emission band (Ir : 642-684 nm) are related to the 4
H11/2 → 4I15/2
,
4
S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions respectively. The UC intensity
increases with increasing Er3+ content, and shows significant quenching beyond 0.5 mole % of Er content. For understanding the luminescence quenching, the critical interatomic distance between the activators becomes important, and is given by Rc 2(3V/4XcZ)1/3 where Xc is the dopant concentration, V is the unit cell volume and Z is the number of host cations. It was also important to consider the coexistence of tetragonal and orthorhombic phases
3
reported in the literature for Sn doped BaTiO3 based on X-ray diffraction analysis [12,14], because a similar coexistence was noted for the 5Er-BSn6T composition investigated in this study. Accordingly
variation in Rc was calculated separately for the two coexisting phases taking into account the variation in the lattice parameters with varying Er content in the two respective phases. For the orthorhombic phase, Rc ~ 5Å with (V=129.662 Å3, Xc=0.5 and Z=4) and for the tetragonal phase Rc~ 4Å with (V=64.208 Å3, Xc=0.5 and Z=4), the determined Rc values support the observed quenching beyond 0.5 mole % of Er. Initial experiments on an unpoled surface of 5Er-BSn6T did not show discernible peaks/kinks in the luminescence intensity corresponding to a phase transition (Fig. 2(a)), and in comparison a poled surface was found to be more effective. Changes in the line intensity of the thermally coupled level centered at (I524) when viewed in a magnified version was more informative as shown in Fig. 2(b). The intensity shows a maximum at the phase transition temperature, and after passing the transition point, it decreases, and then begins to increase again. The reported literature is focused on analyzing the changes occurring in the line intensity, or the intensity ratio of the emission bands (Ig/Ir and Ir/Ig), nonetheless the most effective approach still remains unclear [11]. Figs. 3(a) & (b) show the variations in upconversion spectra at different temperatures. It is noted that the green emission band (Ig2: 540-575 nm) and the red emission band (Ir : 642-684 nm) continuously decrease with temperature, and accordingly the integrated intensity decreases (Fig.3 (d & e)), whereas the intensity of the green band (Ig1: 514-537 nm) shown in Fig.3(c) increase continuously with temperature till the Curie temperature, and shows faint peaks at the phase transitions (TR-O, TO-T and TT-C ). The intensity ratio of the emission bands (Ig1/Ir) did not reveal any useful information on the phase transition. The observed phase transition temperatures by the luminescence method are found to match closely with those determined from dielectric response and heat capacity measurements as shown in Fig.4 and compared in Table 1. The
4
electrical poling treatment results in weak crystal deformation and leads to a change in the local crystal field around the RE ions due to which the UC emission in increased in comparison to the unpoled surface. At the phase transition temperature the changes in the UC intensity are due to changes in the lattice symmetry [15]. Since both surface and sub-surface interactions are involved, surface preparation is of critical importance.
4. Conclusions Changes in the UC luminescence line intensity are more distinct in comparison to the integrated intensity of the green emission band for phase transition detection. An electrically poled surface enables the detection of the three successive ferroelectric phase transitions of 0.5mol% Er doped BaSn0.06Ti0.94O3 by the up conversion luminescence exhibited. Acknowledgements One of the authors Mohd. Azaj Ansari is thankful to University Grant Commission, India for the award of a senior research fellowship No. Ref: FOS-1/114/PhD/4805). References. [1] P.D. Townsend, B. Yang, Y. Wang, Revista Maxicana De Fisica S, 54 (2008) 29-38. [2] G. Canu, G. Bottaro, M.T. Buscaglia, C. Costa, O. Condurache, L. Curecheriu, L. Mitoseriu, V. Buscaglia, L. Armelao, Sci. Rep., 9 (2019) Article No. 6441. [3] Y. Yao, L. Luo, W. Li, J. Zhou, F. Wang. Appl Phys Lett 106 (2015) 082906. [4] J. Wu, Z. Wu, Wu. Mao, Y. Jia. Mater. Lett. 149 (2015) 74–76. [5] Y. Zhang, J. Hao, Mak CL, X.Wei, Opt. Express 19 (2011) 1824-1829. [6] P. Zhang, M. Shen, L. Fang, F. Zheng, X. Wu, J. Shen, H. Chen, Appl. Phys. Lett. 92 (2008) 222908. [7] Y. Wei, Z. Wu, Y. Jia, J. Wu, Y. Shen, H. Luo, Appl. Phys. Lett. 105 (2014) 042902. [8] J. Hao, Y. Zhang, X. Wei, Angew, Chem. Int. Ed. 50 (2011) 6876-6680.
5
[9] J. Wu, W. Mao, Z. Wu, Y. Jia, Mater. Lett. 166 (2016) 75–77. [10] Z. Liang, E. Sun, S. Pei, S. Li, L. Li, F. Qin, Y. Zheng, H. Zhao, Z. Zhang, W. Cao, Opt. Express 24 (2016) 29209-15. [11] Q. Zuo, L. Luo, W. Li and F. Wang, J. Phys. D: Appl. Phys. 49 (2016) 265303 [12] MA. Ansari, K. Sreenivas, Ceram. Int. 45 (2019) 20738˗20749. [13] YA. Zulueta, F. Guerrero, Y. Leyet, J. Anglada-Rivera, RL. Gonzalez Romero, JJ. Melendez Phys. Stat. Sol. 3 (2015) 508-516. [14] V. Mueller and H. Beige, H.-P. Arbicht, C. Eisenschmidt J. Mater. Res. 19 (2004) 2834. [15] H. L. Sun, X. Wu, T. H. Chung, K. W. Kwok, Sci. Rep. 6 (2016) 28677.
Figure and Table captions Figure 1. Room temperature light up-conversion spectra of Ba1-y Ery Sn0.06Ti0.94O3 ceramics with varying Er content (y mole % = 0, 0.1, 0.3, 0.4, 0.5, 0.6, and 0.9), abbreviated as (0ErSn6T…...9Er-BSn6T). Inset: Variation in critical distance Rc and emission line intensities (I524 and I553) with varying Er content. Figure 2(a). Temperature dependence of emission line intensity I524 on poled and unpoled ceramics of 5Er-BSn6T, (b) Magnified view of the emission line intensity at different temperatures around the phase transitions (TR-O, TO-T, and TT-C). Figure 3(a) & (b). Temperature dependence of UC light spectra of 5Er-BSn6T, and integrated intensity of emission bands (c) 514-537 nm, (d) 537-570 nm, and (e) 648-675 nm. Figure 4.Temperature dependence of dielectric constant () and dielectric loss () measured at 1MHz, and heat capacity (Cp). Inset: Magnified view of the weak TR-O phase transition. Table 1. Comparison of phase transition temperatures of 0.5 mol% Er doped BaSn0.06Ti0.96O3 ceramics measured by up-conversion luminescence, dielectric and MDSC techniques.
6
7
8
9
Table 1. Comparison of phase transition temperatures of 0.5 mol% Er doped BaSn0.06Ti0.96O3 ceramics measured by up-conversion luminescence, dielectric and MDSC techniques.
Technique Dielectric constant Dielectric loss MDSC Upconversion luminescence
Temperature dependence T) (T) Cp(T) I524 (T)
TR-O (℃) -9 -12 -10 -12
TO-T (℃) 24 21 22 24
10
TT-C (℃) 78 75 79 74
Highlights
Ferroelectric transitions in Ba0.995Er0.005Sn0.06Ti0.94O3 ceramics are studied. Three successive ferroelectric transitions are detected by luminescence method. Phase detection by luminescence method enhanced on an electrically poled surface. Intensity change in luminescence at 524 nm indicates phase transitions. Phase transitions via luminescence, thermal and dielectric methods match closely.
Author contribution section 1- Mohd azaj Ansari did the experimental work and analyzed the results. 2. K. sreenivas formulated the problems and drafted the manuscript
11
S0167-577X(19)31926-3 https://doi.org/10.1016/j.matlet.2019.127294 MLBLUE 127294
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
30 October 2019 24 December 2019 31 December 2019
Please cite this article as: M.A. Ansari, K. Sreenivas, Detection of rhombo-ortho-tetra-cubic phase transitions on poled Er3+ and Sn4+ doped BaTiO3 ceramics by up-conversion luminescence, Materials Letters (2019), doi: https:// doi.org/10.1016/j.matlet.2019.127294
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier B.V.
Detection of rhombo-ortho-tetra-cubic phase transitions on poled Er3+ and Sn4+ doped BaTiO3 ceramics by up-conversion luminescence
Mohd Azaj Ansaria,*and K. Sreenivasa,* a
Department of Physics & Astrophysics, University of Delhi, Delhi-110007, India
Abstract The three ferroelectric phase transitions rhombohedral-orthorhombic-tetragonal-cubic in 0.5 mole% Er doped BaSn0.06Ti0.94O3 ceramics are detected through up-conversion luminescence measurements. Noticeable changes are observed at the phase transition temperatures in the up-converted emission line intensity at 524 nm and the integrated intensity of the green emission band (514-537 nm) under 980 nm excitation. An electrically poled surface is found to be more sensitive, and the observed phase transition temperatures by the luminescence method are in agreement with the heat capacity and dielectric phase transition temperatures.
Keywords:
Ceramics; Ferroelectrics; Luminescence; Phase transformations
*Corresponding author. Tel.: +91 9810958703, +91 8447038918 E-mail address:
[email protected] (Mohd. Azaj Ansari) [email protected] (K. Sreenivas),
1
1. Introduction Up-conversion photoluminescence (UCPL) measurements have attracted a lot of interest as a new spectroscopic tool to study ferroelectric phase transitions by the non-contact mode [1,2]. Luminescence measurements are found to be sensitive to composition induced changes in lattice symmetry, site selectivity of RE ions, polarization, and temperature induced phase transitions [3,4,5,6]. More recently, interesting revelations through variations in UCPL intensity due to changes in ferroelectric order [1], electrical poling [7], field induced enhancement and modulation in Er/Yb doped BaTiO3 thin films have been reported. [8]. However, studies on different ferroelectric materials for the detection of structural phase transition, the reported literature presents contrasting results. For example: (i) measurements on Er3+ doped (Ba0.97Ca0.03Sn0.06Ti0.94)O3 revealed a broad transition over a wide temperature range (75-550K) [9], (ii) studies on K0.5Na0.5NbO3 ceramic revealed opposite variations in the emission intensity (increasing/decreasing) for the two phase transitions exhibited by K0.5Na0.5NbO3 [10]. Zuo et al. [11] have emphasized that UCPL intensity ratio is more effectual than the changes in emission line intensity.
Sn4+ is known to substitute
preferentially for Ti4+, and decreases the tetragonal-to-cubic (TT-C) phase transition temperature in comparison to undoped BaTiO3 as reported earlier [12]. However, Er3+ with intermediate size can substitute for either/both the cation sites (Ba2+ or Ti4+) with oxygen vacancies. A preferential substitution of Er3+ for Ba2+ has been reported for Ba/Ti<1 upto 2-5 at. %. [2, 13]. The present study is focused on 0.5 mole% Er doped BaSn0.06Ti0.94O3 (5ErBSn6T). A poled ceramic surface is shown to be more effective for the detection of all the three successive structural phase transitions exhibited by Er3+ modified BaSn0.06Ti0.94O3 using the luminescence method. The measured phase transition temperatures are compared with other techniques.
2
2. Materials and methods Ba1-y Ery Sn0.06Ti0.94O3 ceramic compositions with varying Er content (y mole % = 0, 0.1, 0.3, 0.4, 0.5, 0.6, and 0.9, abbreviated as (0Er-BSn6T…...9Er-BSn6T), were prepared by solid-state reaction. High purity Er2O3, BaCO3, TiO2 and SnO2 powders were calcined at 1200° C for 3h, pressed into 1mm thick 10 mm diameter ceramic discs, and sintered at 1350°C for 5h. Novocontrol impedance analyzer, and a modulated differential scanning calorimeter (MDSC) were used for dielectric and heat capacity measurements respectively. For optical measurements, the ceramic was mechanically thinned (0.4mm), polished and reannealed at 1200° C for 2h. Air drying silver paint was used for electroding the ceramics to pole them under a DC field of 12kV/mm for 30 minutes, and later carry out the dielectric measurements at a fixed frequency of 1MHz with 1V perturbing voltage amplitude. For the optical measurements the air drying silver paint was removed gently with acetone. Upconversion luminescence spectra were recorded at 2°C temperature interval using a Quanta master -8450-11 (Horiba) spectrofluorometer, equipped with a cooled detector under 980 nm excitation (laser power 400 mW). 3. Results and Discussion Light upconversion luminescence at room temperature in the prepared Er3+ doped BaSn0.06Ti0.94O3 samples is shown in Fig.1. The observed green emission bands (Ig1: 514-537) and (Ig2: 540-575 nm), and the weak red emission band (Ir : 642-684 nm) are related to the 4
H11/2 → 4I15/2
,
4
S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions respectively. The UC intensity
increases with increasing Er3+ content, and shows significant quenching beyond 0.5 mole % of Er content. For understanding the luminescence quenching, the critical interatomic distance between the activators becomes important, and is given by Rc 2(3V/4XcZ)1/3 where Xc is the dopant concentration, V is the unit cell volume and Z is the number of host cations. It was also important to consider the coexistence of tetragonal and orthorhombic phases
3
reported in the literature for Sn doped BaTiO3 based on X-ray diffraction analysis [12,14], because a similar coexistence was noted for the 5Er-BSn6T composition investigated in this study. Accordingly
variation in Rc was calculated separately for the two coexisting phases taking into account the variation in the lattice parameters with varying Er content in the two respective phases. For the orthorhombic phase, Rc ~ 5Å with (V=129.662 Å3, Xc=0.5 and Z=4) and for the tetragonal phase Rc~ 4Å with (V=64.208 Å3, Xc=0.5 and Z=4), the determined Rc values support the observed quenching beyond 0.5 mole % of Er. Initial experiments on an unpoled surface of 5Er-BSn6T did not show discernible peaks/kinks in the luminescence intensity corresponding to a phase transition (Fig. 2(a)), and in comparison a poled surface was found to be more effective. Changes in the line intensity of the thermally coupled level centered at (I524) when viewed in a magnified version was more informative as shown in Fig. 2(b). The intensity shows a maximum at the phase transition temperature, and after passing the transition point, it decreases, and then begins to increase again. The reported literature is focused on analyzing the changes occurring in the line intensity, or the intensity ratio of the emission bands (Ig/Ir and Ir/Ig), nonetheless the most effective approach still remains unclear [11]. Figs. 3(a) & (b) show the variations in upconversion spectra at different temperatures. It is noted that the green emission band (Ig2: 540-575 nm) and the red emission band (Ir : 642-684 nm) continuously decrease with temperature, and accordingly the integrated intensity decreases (Fig.3 (d & e)), whereas the intensity of the green band (Ig1: 514-537 nm) shown in Fig.3(c) increase continuously with temperature till the Curie temperature, and shows faint peaks at the phase transitions (TR-O, TO-T and TT-C ). The intensity ratio of the emission bands (Ig1/Ir) did not reveal any useful information on the phase transition. The observed phase transition temperatures by the luminescence method are found to match closely with those determined from dielectric response and heat capacity measurements as shown in Fig.4 and compared in Table 1. The
4
electrical poling treatment results in weak crystal deformation and leads to a change in the local crystal field around the RE ions due to which the UC emission in increased in comparison to the unpoled surface. At the phase transition temperature the changes in the UC intensity are due to changes in the lattice symmetry [15]. Since both surface and sub-surface interactions are involved, surface preparation is of critical importance.
4. Conclusions Changes in the UC luminescence line intensity are more distinct in comparison to the integrated intensity of the green emission band for phase transition detection. An electrically poled surface enables the detection of the three successive ferroelectric phase transitions of 0.5mol% Er doped BaSn0.06Ti0.94O3 by the up conversion luminescence exhibited. Acknowledgements One of the authors Mohd. Azaj Ansari is thankful to University Grant Commission, India for the award of a senior research fellowship No. Ref: FOS-1/114/PhD/4805). References. [1] P.D. Townsend, B. Yang, Y. Wang, Revista Maxicana De Fisica S, 54 (2008) 29-38. [2] G. Canu, G. Bottaro, M.T. Buscaglia, C. Costa, O. Condurache, L. Curecheriu, L. Mitoseriu, V. Buscaglia, L. Armelao, Sci. Rep., 9 (2019) Article No. 6441. [3] Y. Yao, L. Luo, W. Li, J. Zhou, F. Wang. Appl Phys Lett 106 (2015) 082906. [4] J. Wu, Z. Wu, Wu. Mao, Y. Jia. Mater. Lett. 149 (2015) 74–76. [5] Y. Zhang, J. Hao, Mak CL, X.Wei, Opt. Express 19 (2011) 1824-1829. [6] P. Zhang, M. Shen, L. Fang, F. Zheng, X. Wu, J. Shen, H. Chen, Appl. Phys. Lett. 92 (2008) 222908. [7] Y. Wei, Z. Wu, Y. Jia, J. Wu, Y. Shen, H. Luo, Appl. Phys. Lett. 105 (2014) 042902. [8] J. Hao, Y. Zhang, X. Wei, Angew, Chem. Int. Ed. 50 (2011) 6876-6680.
5
[9] J. Wu, W. Mao, Z. Wu, Y. Jia, Mater. Lett. 166 (2016) 75–77. [10] Z. Liang, E. Sun, S. Pei, S. Li, L. Li, F. Qin, Y. Zheng, H. Zhao, Z. Zhang, W. Cao, Opt. Express 24 (2016) 29209-15. [11] Q. Zuo, L. Luo, W. Li and F. Wang, J. Phys. D: Appl. Phys. 49 (2016) 265303 [12] MA. Ansari, K. Sreenivas, Ceram. Int. 45 (2019) 20738˗20749. [13] YA. Zulueta, F. Guerrero, Y. Leyet, J. Anglada-Rivera, RL. Gonzalez Romero, JJ. Melendez Phys. Stat. Sol. 3 (2015) 508-516. [14] V. Mueller and H. Beige, H.-P. Arbicht, C. Eisenschmidt J. Mater. Res. 19 (2004) 2834. [15] H. L. Sun, X. Wu, T. H. Chung, K. W. Kwok, Sci. Rep. 6 (2016) 28677.
Figure and Table captions Figure 1. Room temperature light up-conversion spectra of Ba1-y Ery Sn0.06Ti0.94O3 ceramics with varying Er content (y mole % = 0, 0.1, 0.3, 0.4, 0.5, 0.6, and 0.9), abbreviated as (0ErSn6T…...9Er-BSn6T). Inset: Variation in critical distance Rc and emission line intensities (I524 and I553) with varying Er content. Figure 2(a). Temperature dependence of emission line intensity I524 on poled and unpoled ceramics of 5Er-BSn6T, (b) Magnified view of the emission line intensity at different temperatures around the phase transitions (TR-O, TO-T, and TT-C). Figure 3(a) & (b). Temperature dependence of UC light spectra of 5Er-BSn6T, and integrated intensity of emission bands (c) 514-537 nm, (d) 537-570 nm, and (e) 648-675 nm. Figure 4.Temperature dependence of dielectric constant () and dielectric loss () measured at 1MHz, and heat capacity (Cp). Inset: Magnified view of the weak TR-O phase transition. Table 1. Comparison of phase transition temperatures of 0.5 mol% Er doped BaSn0.06Ti0.96O3 ceramics measured by up-conversion luminescence, dielectric and MDSC techniques.
6
7
8
9
Table 1. Comparison of phase transition temperatures of 0.5 mol% Er doped BaSn0.06Ti0.96O3 ceramics measured by up-conversion luminescence, dielectric and MDSC techniques.
Technique Dielectric constant Dielectric loss MDSC Upconversion luminescence
Temperature dependence T) (T) Cp(T) I524 (T)
TR-O (℃) -9 -12 -10 -12
TO-T (℃) 24 21 22 24
10
TT-C (℃) 78 75 79 74
Highlights
Ferroelectric transitions in Ba0.995Er0.005Sn0.06Ti0.94O3 ceramics are studied. Three successive ferroelectric transitions are detected by luminescence method. Phase detection by luminescence method enhanced on an electrically poled surface. Intensity change in luminescence at 524 nm indicates phase transitions. Phase transitions via luminescence, thermal and dielectric methods match closely.
Author contribution section 1- Mohd azaj Ansari did the experimental work and analyzed the results. 2. K. sreenivas formulated the problems and drafted the manuscript
11