NEW CERAMIC MATRIX OF (1-X) LI2LANBTIO7 - (X) TiO2 WITH HIGH THERMAL STABILITY AND RESONANT FREQUENCY TEMPERATURE COEFFICIENT (TF) = + 7.33 PPM.°C-1 IN THE MICROWAVE REGION

Description

[001] This patent application refers to a new ceramic composite generated from the mixture of Li2LaNbTiO7 and TiO2 phases, with proportions of 60% and 40% respectively. This resulted in a thermally stable ceramic with a temperature variation of tf = +7.33 and a resonant frequency of 3.55 GHz, operating within the S-band range. Field of application

[002] The present invention relates to the development of a new ceramic composite with a temperature coefficient at the resonant frequency (tf) in the range of ± 10 ppm.°C1 that operates in the microwave region.

[003] A new ceramic composite consisting of lanthanum lithium titanate (Li2LaNbTiO7) with added titanium dioxide (TiO2) has been developed. This composite has a resonant frequency of 3.55 GHz operating within the S-band range (2 - 4 GHz). This proves that the ceramic composite of this invention can operate in the microwave region and is thermally stable with temperature variation. Practical persuasion

[004] Ceramic materials are inorganic, often crystalline substances that exhibit a wide range of physical, chemical, and mechanical properties that make them unique for technological applications. Among these properties, thermal stability is one of the most important, especially for applications in extreme temperature conditions, such as in the aerospace, electronics, energy, and construction industries.

[005] Thermally stable ceramic materials are essential in various technological applications that demand reliable performance under extreme temperature conditions. Petition 870250062599, dated 07 / 21 / 2025, page 3 / 9 / 7 These materials are designed to exhibit dimensional stability, consistent dielectric properties, and resistance to thermal shock.

[006] The thermal stability of ceramic materials refers to their ability to maintain their mechanical, structural, and functional properties when subjected to high temperatures or thermal cycles. This characteristic is fundamental to preventing failures such as cracks, deformations, or structural collapses. Various classes of ceramics exhibit different levels of thermal stability, which depend on their chemical composition and crystalline structure.

[007] Ceramic materials with high thermal stability play a crucial role in applications requiring reliable performance under extreme conditions. Despite processing and cost challenges, advances in materials technology are expanding their use in innovative sectors such as aerospace, electronics, and energy. Their combination of thermal resistance, chemical stability, and versatility ensures they will remain a cornerstone of modern engineering. Technical persuasion

[008] Studies of new ceramic materials with electrical properties have grown in recent years, being of great interest for the development of projects in the field of telecommunications engineering. The advancement of satellite communication systems and wireless communication systems using microwaves as a carrier has generated a great demand for dielectric resonators, as well as in the field of development of high-performance electronic materials and high-frequency circuits are used from various ceramic composites (MORAIS, JEV; OLIVEIRA, RGM; CASTRO, AJN, SALES, JC; SILVA, MAS; GOES, JC; COSTA, MM; SOMBRA, ASB Dielectric study in the microwave range for ceramic composites based on SnCoN'bOi, and TiO2 mixtures, Journal of Electronic Materials, vol. 46, n. 8, p. 5193-5200, 2017).

[009] Dielectric resonators have gained prominence in wireless communication systems due to their unique properties. These devices, usually manufactured with ceramic materials, have a high dielectric constant and low losses at high frequencies, making them ideal for microwave and millimeter wave frequency applications (ZHENYU, T.; SONG, K.; BAFROOEI, HB; LIU, B.; WU, J.; XU, J.; LIN, H.; WANG, D., The effects Petition 870250062599, dated 07 / 21 / 2025, p. 4 / 9 / 7, regarding the addition of TiO2 to microwave dielectric properties of YsMgAhSiOn ceramics for 5G applications, Ceramics International, vol. 46, p. 15665-15669, 2020).

[010] Ceramics to be used with microwave devices must have electrical constant (er) values ​​above 10 and dielectric loss (tg d) with low values ​​in the microwave region; however, it is common to manufacture ceramic composites in order to obtain these values ​​(SEBASTIAN, M.; UBIC, TR; JANTUNEN, H. Microwave Materials and Applications. UK: Wiley, 2017).

[011] Ceramics must have a stable resonant frequency as a function of temperature change. To be stable, a ceramic must have a temperature coefficient at the resonant frequency (tf) within the range of ± 10 ppm.°C-1. With this value, its resonant frequency does not vary much and preserves its dielectric properties with temperature changes (COURTNEY, WE IEEE Transaction on microwave theory and techniques, vol. 18, p. 476-485, 1970). Therefore, to use a ceramic as a component in the microwave region, it is important to research and study the ceramic phase. State of the art

[012] The search for ceramic materials with electrical and dielectric properties has been an area of ​​intense research in the field of materials science and electronic device engineering. These materials play a crucial role in the manufacture of a wide variety of components, from high-frequency capacitors to highly sensitive temperature sensors. (MT SEBASTIAN, Dielectric Materials for Wireless Communication, Elsevier, San Diego - USA, 2008. https: / / doi.org / 10.1016 / B978-0-08-045330-9.X0001-5).(S. George, MT Sebastian, Synthesis and Microwave Dielectric Properties of Novel Temperature Stable High Q, Li2ATi3O8 (A=Mg, Zn) Ceramics, J. Am. Ceram. 93 (2010) 2164-2166.)

[013] Dielectric ceramics are essential components in the development of electronic devices, both for microwave applications and in the radio frequency range. This is due to the diversity of electrical properties they offer, such as adequate permittivity (τ), temperature coefficients of the resonant frequency close to zero (τ / ), and high quality factors (Qx / ), i.e., low dielectric loss (tan δ). These characteristics make dielectric ceramics ideal for a wide range of devices. (X. Hu, J. Jiang, J. Petition 870250062599, dated 07 / 21 / 2025, page 5 / 9 / 7 Wang, L. Gan, T. Zhang, A new additive-free microwave dielectric ceramic system for LTCC applications: (1 - x)CaWO4 - x(Li0.5Sm0.5)WO4, J. Mater. Sci. Mater. Electron. 31 (2020) 2544-2550. https: / / doi.org / 10.1007 / s10854-019-02791-y), (W. Liu, R. Zuo, A novel Li2TiO3-Li2CeO3 ceramic composite with excellent microwave dielectric properties for low-temperature cofired ceramic applications, J. Eur. Ceram. Soc. 38 (2018) 119-123. https: / / doi.org / 10.1016 / j.jeurceramsoc.2017.07.032).

[014] The Li2LaNbTiÜ7 (LLN) ceramic matrix consists of stacks of two layers of (NbTi) Ü6 octahedra, separated by lithium ions. The lanthanum ions occupy the available spaces in the stacks. The lithium ions, located in spaces between stacks, form edge-sharing LiÜ4 tetrahedra. The tetrahedra are distorted and there are two sets of lithium-oxygen bond lengths, Li — 01 = 2.0184 (%2) and Li — 02 = 2.1043 (%2). Edge-sharing tetrahedra form two-dimensional layers. Objectives of the invention

[015] The objective of the present invention is to propose a new ceramic composite of the Li2LaNbTiÜ7 matrix added with TiÜ2 that exhibits a thermally stable resonance frequency coefficient. Summary of the invention

[016] This patent application refers to a new ceramic composite consisting of a Li2LaNbTiÜ7 matrix with added TiÜ2, where a thermally stable material was found. The proposed new composite could be used in electronic circuits operating in the microwave range. Description of the figures

[017] The following figures are presented to better explain the patent application in an illustrative and non-limiting way: Figure 1 shows the results of the XRD powder standard of Li2LaNbTiÜ7 synthesized by the solid-state reaction method. The XRD standard exhibits sharp diffraction peaks, where all peaks can be well indexed to the Li2LaNbTiÜ7 phase (ICSD No. 88967). Petition 870250062599, dated 07 / 21 / 2025, page 6 / 9 5 / 7 No additional peaks of other phases were found, indicating the formation of the pure LÍ2LaNbTiC>7 phase under such experimental conditions; Figure 2: Figure 2 highlights the experimental setup for measuring the temperature coefficient of the resonant frequency (τ / ), where the experimental arrangement used is a cylindrical dielectric resonator antenna (DRA). The structure includes a ground plane (I), where a heating chamber made of refractory ceramic (II) is located, surrounded by electrical resistors (III) inside. Inside the refractory ceramic is the sample (IV), which is next to an 8 mm probe (V) connected to a coaxial cable that is connected to an N5230A network analyzer. Temperature control is achieved by a thermocouple (VI). In this measurement, the HE nd mode was used. Figure 3: Figure 3 shows the T / values ​​of the LNN ceramic and the composites as a function of the mass percentage of T1O2 added to the LNN. It can be observed that, with the increase of titanium dioxide in the ceramic, the T / values ​​increase, where in the composite with 40% T1O2 in the LÍ2LaNbTiC>7 ceramic matrix, the T / value is +7.33 ppm / C'1, a value within the range of ± 10 ppm^C'1. This shows that this composite has thermal stability. Detailed description of the invention

[018] The ceramic matrix LÍ2LaNbTiC>7 (LLN) was prepared by the solid-state reaction method using the oxides L12CO3 (Aldrich, 99.8%), La2Ü3 (Vetec, 99.9%), Nb2Os (Aldrich, 99.8%) and T1O2 (Aldrich, 99.8%). The oxides were weighed stoichiometrically to obtain the LNN phase. Equation (1) shows the reaction describing the formation of the phase. Li2CO^+La2O^s)+ NB2O5+ TtO2Li2LaNbTiO7(s) + CO2(g) (1)

[019] After weighing, the oxides were ground in a high-energy planetary mill (Fritsch Pulverisette 5). Grinding was carried out at an angular speed of 360 rpm for 4 hours. Then the resulting powder was calcined at 1050°C for 4 hours.

[020] The crystalline phase of LNN was characterized by X-ray diffraction and the confirmation of the LNN ceramic phase was through refinement of the experimental diffractogram by the Rietveld method. The parameters of the Rietveld refinement of the LNN matrix were: Rwp = 5.42; χ2 = 2.40 and RBragg = 7.18, where the parameters obtained are within the limits, showing Petition 870250062599, dated 07 / 21 / 2025, page 7 / 9 6 / 7 that the refinement performed shows good reliability and confirms the obtaining of the LNN ceramic phase.

[021] For the fabrication of LNN DRA, a portion of LNN was placed in a cylindrical mold and pressed using uniaxial pressure with a load of 97.55 MPa for 5 minutes, to form a cylindrical piece. Immediately afterwards, the sample was sintered in a muffle furnace at a temperature of 1150 °C for 4 hours and a heating rate of 5 °C.min⁻¹.

[022] For the fabrication of the composite DRA, a portion of T1O2 was added and mixed into the LNN matrix. The mixed sample was pressed into a cylindrical mold using uniaxial pressure with a load of 97.55 MPa for 5 minutes to form a cylindrical piece. Immediately after, the sample was sintered in a muffle furnace at a temperature of 1150 °C for 4 hours and a heating rate of 5 °C.min⁻¹. The synthesis of the LNN matrix and the L12LaNbTiO7-TiC₂ composites was carried out to observe the dielectric characteristics of this ceramic system. In this invention, it was planned to obtain a series of composites with different concentrations of T1O2 in the LNN matrix; thus, titanium dioxide additions were made in molar proportions of 5, 20, 40, 60, and 80%.

[023] The thermal stability assessment of LNN ADRs and composites was performed by measuring the temperature coefficient of resonant frequency (τ / ) using the method described by Silva-Fernandes-Sombra (SFS) (SILVA, MAS; FERNANDES, TSM; SOMBRA, ASB. An alternative method for the measurement of the microwave temperature coefficient of resonant frequency (τ / ). Journal of Applied Physics, vol.

[024] The thermal stability study of LNN ceramics and composites was carried out, and the results obtained showed that the Δt / of the Li2LaNbTiO7 phase is -36.39 ppmfC₁₀, which makes it impossible for the LNN matrix to be a thermally stable device in the microwave region. Therefore, it became necessary to obtain ceramic composites from Li2LaNbTiO₇ that operate in the microwave region and have thermal stability. One of the ceramics that exhibits good dielectric properties is Li₂T₁O₂, which is frequently added to ceramic matrices to improve dielectric properties (SEBASTIAN, M.; UBIC, TR; JANTUNEN, H.). Petition 870250062599, dated 07 / 21 / 2025, page 8 / 9 / 7 Microwave Materials and Applications. UK: Wiley, 2017). Therefore, a study was conducted on the addition of TiO2 to the Li2LaNbTiO7 ceramic matrix to obtain a device that operates in the microwave region and has thermal stability.

Claims

CLAIMS 1. High thermal stability of the ceramic composite (1-x) Li2LaNbTiO7 - (x) TiO2 with a resonant frequency temperature coefficient of τχ =+7.33 ppm.°C-1 in the microwave region, characterized by employing a Li2LaNbTiO7 - TiO2 ceramic composite, synthesized by a solid-state reaction to find a thermally stable material with temperature variation.

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