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Low temperature sintering and microwave dielectric properties of LiMBO3 (M=Ca, Sr) ceramics
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CERAMICS INTERNATIONAL
Ceramics International 42 (2016) 6475–6479 www.elsevier.com/locate/ceramint
Short communication
Low temperature sintering and microwave dielectric properties of LiMBO3 (M ¼Ca, Sr) ceramics Liu Yanpeng, Wang Yongnan, Li Yumin, Bian Jianjiang Department of Inorganic Materials, Shanghai University, 333 Nanchen Road, Shanghai 200444, China Received 18 December 2015; received in revised form 21 December 2015; accepted 21 December 2015 Available online 30 December 2015
Abstract LiMBO3 (M ¼Ca, Sr) ceramics have been prepared by a traditional ceramic process. The microstructure and chemical compatibility with Ag were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Microwave dielectric properties were measured with a network analyzer. LiMBO3 (M ¼ Ca, Sr) ceramics could be densified at 800 1C. Secondary phases appeared with the further increase in sintering temperature due to the possible evaporation of boron. The Q f values of LiMBO3 (M ¼Ca, Sr) strongly depended on sintering temperature, and decreased remarkably with the further increase in sintering temperature higher than 800 1C. Optimized microwave dielectric properties with εr ¼8.7, Q f ¼75000 GHz, τf ¼ 150 ppm/1C and εr ¼ 8.6, Q f ¼60000 GHz, τf ¼ 39 ppm/1C could be obtained for LiCaBO3 and LiSrBO3, respectively, after sintering at the 800 1C for 2 h. LiMBO3 (M¼ Ca, Sr) ceramics could be chemically compatible with Ag after sintering at 800 1C/2 h. & 2016 Published by Elsevier Ltd and Techna Group S.r.l.
Keywords: LTCC; Microwave dielectric properties
1. Introduction Low-temperature co-fired ceramic (LTCC) technology requires the dielectric ceramics to have a lower sintering temperature than the melting point of inner electrode materials, such as Ag, Cu. Reducing the sintering temperature without affecting the dielectric properties is strongly required in LTCC material research. Recently glass-free LTCC materials with appropriate microwave dielectric properties have been intensively investigated for the multilayer structure applications [1–10]. A few of glass-free LTCC green tape have been developed [11–12]. Lithium or boron containing compounds usually have low melting points and hence low sintering temperatures. Synthesis and structures of new lithium containing borates LiMBO3 (M ¼ Ca, Sr) have been reported [13–14]. LiCaBO3 and LiSrBO3 were considered to have orthorhombic Pbca and monoclinic P21/c space group, respectively. The luminescent properties of the rare earth-doped LiMBO3 (M ¼ Ca, Sr) have also been investigated [15–16]. However, to the best of our knowledge, no reference about the sintering behavior, microwave dielectric properties of LiMBO3 (M ¼ Ca, http://dx.doi.org/10.1016/j.ceramint.2015.12.117 0272-8842/& 2016 Published by Elsevier Ltd and Techna Group S.r.l.
Sr) and their chemical compatibility with silver has been reported. In this paper, therefore, we investigated the sinterabilities and microwave dielectric properties of LiMBO3 (M ¼ Ca, Sr) ceramics and their chemical compatibilities with silver at sintering temperature in order to find their possible applications in LTCC technology. 2. Experimental LiMBO3 (M ¼ Ca, Sr) ceramics were prepared by conventional solid-state reaction process from the starting materials including Li2CO3 (99.9%), B2O3 (99.9%), CaCO3 (99.6%) and SrCO3(99.5%). The starting materials were weighed according to the above formula and ball milled in acetone with zirconia milling media for 24 h, then dried and calcined 750 1C/72 h in alumina crucible. The calcined powders were pulverized again by ball milling in acetone for 24 h. The ground powders were dried, then mixed with 7 wt%–10 wt% PVA as binder and granulated. The granulated powders were uni-axially pressed into compacts 10 mm in diameter and 4.5–5.5 mm in height under the pressure of 100 Mpa. The pellets were sintered at
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775 1C to 875 1C for 2 h. The sintering temperature was optimized by the maximum bulk density and Q f value. In order to prevent lithium and boron evaporation during the sintering, the compacts were covered with sacrificial powder of the same composition. The chemical compatibility with silver was investigated by cofiring the mixed powders with pure silver powders (30 wt% Ag) in ambient atmosphere at temperatures of 800 1C for 2 h. The densities of the ceramics were measured using the Archimedes' method. The phase compositions of the sintered specimens were identified using X-ray powder diffraction (XRD) with Ni-filtered CuKα radiation (Rigaku D/max2550, Tokyo, Japan). The microstructure of sintered sample was characterized by scanning electron microscopy (SEM, JSM6700F, Japan). All samples were polished. Microwave dielectric properties of the sintered specimens were measured at about 9–13 GHz using a network analyzer (Model N5230A, Agilent, Palo Alto, CA). The quality factor was measured according to the Hakki–Coleman method with the TE011 resonant mode, and the temperature coefficient of the resonator frequency (τf) was measured using an invar cavity in the temperature range from 20 1C to 80 1C. 3. Results and discussion Fig. 1 shows the powder XRD patterns of LiMBO3 (M ¼ Ca, Sr) ceramics sintered at 800 1C/2 h. All the reflections could be indexed according to the orthorhombic Pbca and monoclinic P21/c space group for LiCaBO3 and LiSrBO3, respectively, which is in agreement with the Refs. [13–14]. Fig. 2 illustrates the variation of relative density with sintering temperature. The density of LiCaBO3 is higher than that of LiSrBO3 for given sintering temperature, and maximum density of about 92–94% could be obtained at 800 1C/2 h for both of LiCaBO3 and LiSrBO3. The decrease in density with further increasing sintering temperature can be associated with the possible evaporation of boron, although sacrificial powder of the same composition was adopted during the sintering process. Fig. 3 shows the typical back scattering SEM images LiMBO3 (M ¼ Ca, Sr) sintered at 800 1C/2 h and 875 1C/2 h. LiMBO3
Fig. 2. Variation of densities of LiMBO3 (M¼ Ca, Sr) ceramics as function of sintering temperature.
(M ¼ Ca, Sr) ceramics sintered at 800 1C/2 h demonstrate single phase, which is accordance with the XRD results. However, the specimens sintered at 875 1C/2 h exhibit secondary phases due to possible evaporation of boron. The accurate composition of the secondary phase could not be identified, since lithium could not be detected by EDS analysis. Microwave dielectric properties of LiCaBO3 and LiSrBO3 ceramics sintered at different temperatures are shown in Fig. 4. Dielectric permittivities of LiCaBO3 and LiSrBO3 are around 8.6, which change little with sintering temperature, although secondary phases appeared in the samples with the further increase in sintering temperature. It seems to imply that the secondary phase has similar dielectric permittivity as that of the matrix. The Q f value of LiCaBO3 is larger than that of LiSrBO3. The Q f value decreases remarkably both for LiCaBO3 and LiSrBO3 when the sintering is higher than 800 1C/2 h, which can be ascribed to the appearance of secondary phases with the further increase in sintering temperature as shown in Fig. 3. Both LiCaBO3 and LiSrBO3 demonstrate negative value of temperature coefficient of resonant frequency (τf). The absolute value of τf of LiCaBO3 is much larger than that of LiSrBO3. Optimized microwave dielectric properties with εr ¼ 8.7, Q f¼ 75000 GHz, τf ¼ 150 ppm/1C and εr ¼ 8.6, Q f¼ 60000 GHz, τf ¼ 39 ppm/1C could be obtained for LiCaBO3 and LiSrBO3, respectively, after sintering at the 800 1C for 2 h. Fig. 5 shows the powder XRD patterns of LiMBO3 (M¼ Ca, Sr) ceramics cofired with Ag at 800 1C for 2 h. Except for the reflections from the LiMBO3 (M¼ Ca, Sr), the peaks of pure silver phase (Ag) could also be observed, which means that the silver did not react with the matrix after sintering at 800 1C/2 h. The corresponding back-scattered SEM images demonstrate two distinct phases including Ag and matrix (Fig. 6). No visible interaction layer or other reaction products were detected, which is in agreement with the XRD result as shown in Fig. 5. 4. Conclusions
Fig. 1. Powder XRD patterns of LiMBO3 (M ¼Ca, Sr) sintered at 800 1C/2 h.
Microstructure, sintering behavior, microwave dielectric properties of LiMBO3 (M¼ Ca, Sr) ceramics and their chemical
L. Yanpeng et al. / Ceramics International 42 (2016) 6475–6479
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Fig. 3. Back scattering SEM images of (a) LiCaBO3 and (b) LiSrBO3 sintered at 800 1C/2 h and 875 1C/2 h.
Fig. 5. Powder XRD patterns of LiMBO3 (M¼ Ca, Sr) cofired with 30 wt% Ag at 800 1C/2 h.
Fig. 4. Microwave dielectric properties of LiMBO3 (M¼ Ca, Sr) ceramics as function of sintering temperature.
compatibilities with silver (Ag) powders have been investigated in this paper. Both samples could be densified at 800 1C/2 h. Secondary phases existed in the samples sintered at 875 1C/2 h due to the possible evaporation of boron. Both samples exhibited negative τf value and εr of 8.6. The Q f values of both samples strongly depended on sintering temperature, and decreased remarkably with the further increase in sintering temperature higher than 800 1C. Optimized microwave dielectric properties with εr ¼ 8.7, Q f¼ 75000 GHz, τf ¼ 150 ppm/1C and εr ¼ 8.6, Q f¼ 60000 GHz, τf ¼ 39 ppm/1C
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Fig. 6. Back scattering SEM images of LiMBO3 (M ¼Ca, Sr) cofired with 30 wt% Ag at 800 1C/2 h.
could be obtained for LiCaBO3 and LiSrBO3, respectively, after sintering at the 800 1C for 2 h. The XRD and back scattering SEM analysis shows that the ceramics were chemically compatible with Ag powders after sintering at 800 1C/2 h. References [1] M.T. Sebastian, H. Jantunen, Low loss dielectric materials for LTCC applications: a review, Int. Mater. Rev. 53 (2008) 57–90. [2] M.T. Sebastiana, R. Ubic, H. Jantunen, Low-loss dielectric ceramic materials and their properties, Int. Mater. Rev. 60 (7) (2015) 392–412. [3] J.J. Bian, J.Y. Wu, L. Wang, Structural evolution, sintering behavior and microwave dielectric properties of (1 x)Li3NbO4–xLiF (0 rxr 0.9), J. Eur. Ceram. Soc. 32 (2012) 1251–1259. [4] M. Valant, D. Suvorov, Glass-free low-temperature cofired ceramics: calcium germanates, silicates and tellurates, J. Eur. Ceram. Soc. 24 (2004) 1715–1719. [5] J.J. Bain, D.W. Kim, K.S. Hong, Glass-free LTCC microwave dielectric ceramics, Mater. Res. Bull. 40 (2005) 2120–2129.
[6] G. Subodh, M.T. Sebastian, Glass-free Zn2Te3O8 microwave ceramic for LTCC applications, J. Am. Ceram. Soc. 90 (7) (2007) 2266–2268. [7] D.K. Kwon, M.T. Lanagan, T.R. Shrout, Microwave dielectric properties and low-temperature cofiring of BaTe4O9 with aluminum metal electrode, J. Am. Ceram. Soc. 88 (12) (2005) 3409–3412. [8] D. Zhou, C.A. Randall, L.X. Pang, H. Wang, X.-G. Wu, J. Guo, G.Q. Zhang, L. Shui, X. Yao, Microwave dielectric properties of Li2(M2 þ )2Mo3O12 and Li3(M3 þ )Mo3O12 (M¼ Zn, Ca, Al, and In) lyonsite-related-type ceramics with ultra-low sintering Temperatures, J. Am. Ceram. Soc. 94 (3) (2011) 802–805. [9] J. Li, L. Fang, H. Luo, J. Khaliq, Y. Tang, C.C. Li, Li4WO5: a temperature stable low-firing microwave dielectric ceramic with rock salt structure, J. Eur. Ceram. Soc. 36 (1) (2016) 243–246. [10] D. Thomas, M.T. Sebastian, Temperature compensated LiMgPO4: a new glass free low temperature cofired ceramic, J. Am. Ceram. Soc. 93 (2010) 3828–3831. [11] D. Thomas, P. Abhilash, M.T. Sebastian, Casting and characterization of LiMgPO4 glass free LTCC tape for microwave applications, J. Eur. Ceram. Soc. 33 (2013) 87–93.
L. Yanpeng et al. / Ceramics International 42 (2016) 6475–6479 [12] P. Abilash, M.T. Sebastian, K.P. Surendran, Glass free non-aqeous Bi4 (SiO4)3 LTCC tapes, J. Eur. Ceram. Soc. 35 (2015) 2313–2320. [13] L. Wu, X.L. Chen, H. Li, Structure determination of a new compound LiCaBO3, J. Solid State Chem. 177 (4) (2004) 1111–1116. [14] W.D. Cheng, H. Zhang, Q.S. Lin, Syntheses, crystal and electronic structures, and linear optics of LiMBO3 (M ¼Sr, Ba) orthoborates, Chem. Mater. 13 (5) (2001) 1841–1847.
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[15] P. Li, Z. Wang, Z. Yang, Luminescent characteristics of LiCaBO3: M (M¼ Eu3 þ , Sm3 þ , Tb3 þ , Ce3 þ , Dy3 þ ) phosphor for white LED, J. Lumin. 130 (2) (2010) 222–225. [16] P. Li, Z. Wang, Z. Yang, Luminescent characteristics of LiSrBO3: M (M¼ Eu3 þ , Sm3 þ , Tb3 þ , Ce3 þ , Dy3 þ ) phosphor for white lightemitting diode, Mater. Res. Bull. 44 (11) (2009) 2068–2071.
CERAMICS INTERNATIONAL
Ceramics International 42 (2016) 6475–6479 www.elsevier.com/locate/ceramint
Short communication
Low temperature sintering and microwave dielectric properties of LiMBO3 (M ¼Ca, Sr) ceramics Liu Yanpeng, Wang Yongnan, Li Yumin, Bian Jianjiang Department of Inorganic Materials, Shanghai University, 333 Nanchen Road, Shanghai 200444, China Received 18 December 2015; received in revised form 21 December 2015; accepted 21 December 2015 Available online 30 December 2015
Abstract LiMBO3 (M ¼Ca, Sr) ceramics have been prepared by a traditional ceramic process. The microstructure and chemical compatibility with Ag were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Microwave dielectric properties were measured with a network analyzer. LiMBO3 (M ¼ Ca, Sr) ceramics could be densified at 800 1C. Secondary phases appeared with the further increase in sintering temperature due to the possible evaporation of boron. The Q f values of LiMBO3 (M ¼Ca, Sr) strongly depended on sintering temperature, and decreased remarkably with the further increase in sintering temperature higher than 800 1C. Optimized microwave dielectric properties with εr ¼8.7, Q f ¼75000 GHz, τf ¼ 150 ppm/1C and εr ¼ 8.6, Q f ¼60000 GHz, τf ¼ 39 ppm/1C could be obtained for LiCaBO3 and LiSrBO3, respectively, after sintering at the 800 1C for 2 h. LiMBO3 (M¼ Ca, Sr) ceramics could be chemically compatible with Ag after sintering at 800 1C/2 h. & 2016 Published by Elsevier Ltd and Techna Group S.r.l.
Keywords: LTCC; Microwave dielectric properties
1. Introduction Low-temperature co-fired ceramic (LTCC) technology requires the dielectric ceramics to have a lower sintering temperature than the melting point of inner electrode materials, such as Ag, Cu. Reducing the sintering temperature without affecting the dielectric properties is strongly required in LTCC material research. Recently glass-free LTCC materials with appropriate microwave dielectric properties have been intensively investigated for the multilayer structure applications [1–10]. A few of glass-free LTCC green tape have been developed [11–12]. Lithium or boron containing compounds usually have low melting points and hence low sintering temperatures. Synthesis and structures of new lithium containing borates LiMBO3 (M ¼ Ca, Sr) have been reported [13–14]. LiCaBO3 and LiSrBO3 were considered to have orthorhombic Pbca and monoclinic P21/c space group, respectively. The luminescent properties of the rare earth-doped LiMBO3 (M ¼ Ca, Sr) have also been investigated [15–16]. However, to the best of our knowledge, no reference about the sintering behavior, microwave dielectric properties of LiMBO3 (M ¼ Ca, http://dx.doi.org/10.1016/j.ceramint.2015.12.117 0272-8842/& 2016 Published by Elsevier Ltd and Techna Group S.r.l.
Sr) and their chemical compatibility with silver has been reported. In this paper, therefore, we investigated the sinterabilities and microwave dielectric properties of LiMBO3 (M ¼ Ca, Sr) ceramics and their chemical compatibilities with silver at sintering temperature in order to find their possible applications in LTCC technology. 2. Experimental LiMBO3 (M ¼ Ca, Sr) ceramics were prepared by conventional solid-state reaction process from the starting materials including Li2CO3 (99.9%), B2O3 (99.9%), CaCO3 (99.6%) and SrCO3(99.5%). The starting materials were weighed according to the above formula and ball milled in acetone with zirconia milling media for 24 h, then dried and calcined 750 1C/72 h in alumina crucible. The calcined powders were pulverized again by ball milling in acetone for 24 h. The ground powders were dried, then mixed with 7 wt%–10 wt% PVA as binder and granulated. The granulated powders were uni-axially pressed into compacts 10 mm in diameter and 4.5–5.5 mm in height under the pressure of 100 Mpa. The pellets were sintered at
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775 1C to 875 1C for 2 h. The sintering temperature was optimized by the maximum bulk density and Q f value. In order to prevent lithium and boron evaporation during the sintering, the compacts were covered with sacrificial powder of the same composition. The chemical compatibility with silver was investigated by cofiring the mixed powders with pure silver powders (30 wt% Ag) in ambient atmosphere at temperatures of 800 1C for 2 h. The densities of the ceramics were measured using the Archimedes' method. The phase compositions of the sintered specimens were identified using X-ray powder diffraction (XRD) with Ni-filtered CuKα radiation (Rigaku D/max2550, Tokyo, Japan). The microstructure of sintered sample was characterized by scanning electron microscopy (SEM, JSM6700F, Japan). All samples were polished. Microwave dielectric properties of the sintered specimens were measured at about 9–13 GHz using a network analyzer (Model N5230A, Agilent, Palo Alto, CA). The quality factor was measured according to the Hakki–Coleman method with the TE011 resonant mode, and the temperature coefficient of the resonator frequency (τf) was measured using an invar cavity in the temperature range from 20 1C to 80 1C. 3. Results and discussion Fig. 1 shows the powder XRD patterns of LiMBO3 (M ¼ Ca, Sr) ceramics sintered at 800 1C/2 h. All the reflections could be indexed according to the orthorhombic Pbca and monoclinic P21/c space group for LiCaBO3 and LiSrBO3, respectively, which is in agreement with the Refs. [13–14]. Fig. 2 illustrates the variation of relative density with sintering temperature. The density of LiCaBO3 is higher than that of LiSrBO3 for given sintering temperature, and maximum density of about 92–94% could be obtained at 800 1C/2 h for both of LiCaBO3 and LiSrBO3. The decrease in density with further increasing sintering temperature can be associated with the possible evaporation of boron, although sacrificial powder of the same composition was adopted during the sintering process. Fig. 3 shows the typical back scattering SEM images LiMBO3 (M ¼ Ca, Sr) sintered at 800 1C/2 h and 875 1C/2 h. LiMBO3
Fig. 2. Variation of densities of LiMBO3 (M¼ Ca, Sr) ceramics as function of sintering temperature.
(M ¼ Ca, Sr) ceramics sintered at 800 1C/2 h demonstrate single phase, which is accordance with the XRD results. However, the specimens sintered at 875 1C/2 h exhibit secondary phases due to possible evaporation of boron. The accurate composition of the secondary phase could not be identified, since lithium could not be detected by EDS analysis. Microwave dielectric properties of LiCaBO3 and LiSrBO3 ceramics sintered at different temperatures are shown in Fig. 4. Dielectric permittivities of LiCaBO3 and LiSrBO3 are around 8.6, which change little with sintering temperature, although secondary phases appeared in the samples with the further increase in sintering temperature. It seems to imply that the secondary phase has similar dielectric permittivity as that of the matrix. The Q f value of LiCaBO3 is larger than that of LiSrBO3. The Q f value decreases remarkably both for LiCaBO3 and LiSrBO3 when the sintering is higher than 800 1C/2 h, which can be ascribed to the appearance of secondary phases with the further increase in sintering temperature as shown in Fig. 3. Both LiCaBO3 and LiSrBO3 demonstrate negative value of temperature coefficient of resonant frequency (τf). The absolute value of τf of LiCaBO3 is much larger than that of LiSrBO3. Optimized microwave dielectric properties with εr ¼ 8.7, Q f¼ 75000 GHz, τf ¼ 150 ppm/1C and εr ¼ 8.6, Q f¼ 60000 GHz, τf ¼ 39 ppm/1C could be obtained for LiCaBO3 and LiSrBO3, respectively, after sintering at the 800 1C for 2 h. Fig. 5 shows the powder XRD patterns of LiMBO3 (M¼ Ca, Sr) ceramics cofired with Ag at 800 1C for 2 h. Except for the reflections from the LiMBO3 (M¼ Ca, Sr), the peaks of pure silver phase (Ag) could also be observed, which means that the silver did not react with the matrix after sintering at 800 1C/2 h. The corresponding back-scattered SEM images demonstrate two distinct phases including Ag and matrix (Fig. 6). No visible interaction layer or other reaction products were detected, which is in agreement with the XRD result as shown in Fig. 5. 4. Conclusions
Fig. 1. Powder XRD patterns of LiMBO3 (M ¼Ca, Sr) sintered at 800 1C/2 h.
Microstructure, sintering behavior, microwave dielectric properties of LiMBO3 (M¼ Ca, Sr) ceramics and their chemical
L. Yanpeng et al. / Ceramics International 42 (2016) 6475–6479
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Fig. 3. Back scattering SEM images of (a) LiCaBO3 and (b) LiSrBO3 sintered at 800 1C/2 h and 875 1C/2 h.
Fig. 5. Powder XRD patterns of LiMBO3 (M¼ Ca, Sr) cofired with 30 wt% Ag at 800 1C/2 h.
Fig. 4. Microwave dielectric properties of LiMBO3 (M¼ Ca, Sr) ceramics as function of sintering temperature.
compatibilities with silver (Ag) powders have been investigated in this paper. Both samples could be densified at 800 1C/2 h. Secondary phases existed in the samples sintered at 875 1C/2 h due to the possible evaporation of boron. Both samples exhibited negative τf value and εr of 8.6. The Q f values of both samples strongly depended on sintering temperature, and decreased remarkably with the further increase in sintering temperature higher than 800 1C. Optimized microwave dielectric properties with εr ¼ 8.7, Q f¼ 75000 GHz, τf ¼ 150 ppm/1C and εr ¼ 8.6, Q f¼ 60000 GHz, τf ¼ 39 ppm/1C
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Fig. 6. Back scattering SEM images of LiMBO3 (M ¼Ca, Sr) cofired with 30 wt% Ag at 800 1C/2 h.
could be obtained for LiCaBO3 and LiSrBO3, respectively, after sintering at the 800 1C for 2 h. The XRD and back scattering SEM analysis shows that the ceramics were chemically compatible with Ag powders after sintering at 800 1C/2 h. References [1] M.T. Sebastian, H. Jantunen, Low loss dielectric materials for LTCC applications: a review, Int. Mater. Rev. 53 (2008) 57–90. [2] M.T. Sebastiana, R. Ubic, H. Jantunen, Low-loss dielectric ceramic materials and their properties, Int. Mater. Rev. 60 (7) (2015) 392–412. [3] J.J. Bian, J.Y. Wu, L. Wang, Structural evolution, sintering behavior and microwave dielectric properties of (1 x)Li3NbO4–xLiF (0 rxr 0.9), J. Eur. Ceram. Soc. 32 (2012) 1251–1259. [4] M. Valant, D. Suvorov, Glass-free low-temperature cofired ceramics: calcium germanates, silicates and tellurates, J. Eur. Ceram. Soc. 24 (2004) 1715–1719. [5] J.J. Bain, D.W. Kim, K.S. Hong, Glass-free LTCC microwave dielectric ceramics, Mater. Res. Bull. 40 (2005) 2120–2129.
[6] G. Subodh, M.T. Sebastian, Glass-free Zn2Te3O8 microwave ceramic for LTCC applications, J. Am. Ceram. Soc. 90 (7) (2007) 2266–2268. [7] D.K. Kwon, M.T. Lanagan, T.R. Shrout, Microwave dielectric properties and low-temperature cofiring of BaTe4O9 with aluminum metal electrode, J. Am. Ceram. Soc. 88 (12) (2005) 3409–3412. [8] D. Zhou, C.A. Randall, L.X. Pang, H. Wang, X.-G. Wu, J. Guo, G.Q. Zhang, L. Shui, X. Yao, Microwave dielectric properties of Li2(M2 þ )2Mo3O12 and Li3(M3 þ )Mo3O12 (M¼ Zn, Ca, Al, and In) lyonsite-related-type ceramics with ultra-low sintering Temperatures, J. Am. Ceram. Soc. 94 (3) (2011) 802–805. [9] J. Li, L. Fang, H. Luo, J. Khaliq, Y. Tang, C.C. Li, Li4WO5: a temperature stable low-firing microwave dielectric ceramic with rock salt structure, J. Eur. Ceram. Soc. 36 (1) (2016) 243–246. [10] D. Thomas, M.T. Sebastian, Temperature compensated LiMgPO4: a new glass free low temperature cofired ceramic, J. Am. Ceram. Soc. 93 (2010) 3828–3831. [11] D. Thomas, P. Abhilash, M.T. Sebastian, Casting and characterization of LiMgPO4 glass free LTCC tape for microwave applications, J. Eur. Ceram. Soc. 33 (2013) 87–93.
L. Yanpeng et al. / Ceramics International 42 (2016) 6475–6479 [12] P. Abilash, M.T. Sebastian, K.P. Surendran, Glass free non-aqeous Bi4 (SiO4)3 LTCC tapes, J. Eur. Ceram. Soc. 35 (2015) 2313–2320. [13] L. Wu, X.L. Chen, H. Li, Structure determination of a new compound LiCaBO3, J. Solid State Chem. 177 (4) (2004) 1111–1116. [14] W.D. Cheng, H. Zhang, Q.S. Lin, Syntheses, crystal and electronic structures, and linear optics of LiMBO3 (M ¼Sr, Ba) orthoborates, Chem. Mater. 13 (5) (2001) 1841–1847.
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[15] P. Li, Z. Wang, Z. Yang, Luminescent characteristics of LiCaBO3: M (M¼ Eu3 þ , Sm3 þ , Tb3 þ , Ce3 þ , Dy3 þ ) phosphor for white LED, J. Lumin. 130 (2) (2010) 222–225. [16] P. Li, Z. Wang, Z. Yang, Luminescent characteristics of LiSrBO3: M (M¼ Eu3 þ , Sm3 þ , Tb3 þ , Ce3 þ , Dy3 þ ) phosphor for white lightemitting diode, Mater. Res. Bull. 44 (11) (2009) 2068–2071.