RU2542009C1 - Piezoelectric ceramic material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: piezoelectric ceramic material contains the following components, wt %: Na₂O 8.61-8.70; K₂O 11.15-11.26; Li₂O 0.49-0.50; Ta₂O₅ 11.37-11.49; Nb₂O₃ 61.59-62.19; Bi₂O₃ 0.37-1.10; Fe₂O₃ 0.13-0.38; Sb₂O₅ 5.31-5.37.

EFFECT: high electromechanical coupling factor of the planar oscillation mode and low relative permittivity.

3 ex, 3 tbl

Description

The invention relates to piezoelectric ceramic materials based on sodium, potassium, lithium niobates and can be used in high-frequency ultrasonic piezoelectric transducers designed to operate in air as emitters and receivers in remote control systems, proximity indicators of obstacles, in devices for measuring gas velocity flow.

, ~ 600, достаточно высокими пьезомодулем d₃₃ (≥150 пКл/Н), пьезочувствительностью, g₃₃, (~30 мВ·м/Н), коэффициентом электромеханической связи планарной моды колебаний, К_р (≥0.50), низкой механической добротностью, Q_M, (<150).For these applications, the material should have a low relative permittivity of polarized samples, $${\epsilon }_{33}^T/{\epsilon }_0$$

, ~ 600, a sufficiently high piezoelectric module d ₃₃ (≥150 pC / N), piezoelectric sensitivity, g ₃₃ , (~ 30 mV · m / N), the electromechanical coupling coefficient of the planar oscillation mode, K _p (≥0.50), low mechanical quality factor, Q _M , (<150).

, d₃₃=200 пКл/Н, g₃₃=19 пКл/Н, К_р=0.43 [1]. Для указанных применений материал имеет слишком высокое значение $${\epsilon }_{33}^T/{\epsilon }_0$$

и низкую g₃₃.Known piezoelectric ceramic material based on niobates of sodium, potassium, lithium, including Na ₂ O, K ₂ O, Li ₂ O, Nb ₂ O ₅ , Ta ₂ O ₅ , Sb ₂ O ₅ , CeO ₂ and MnO ₂ . The composition of the material corresponds to the chemical formula (Na _0.475 K _0.475 Li _0.05 ) (Nb _0.92 Ta _0.05 , Sb _0.03 ) O ₃ + 0.4% CeO ₂ + 0.4% MnO ₂ . Material has (for better formulations) $${\epsilon }_{33}^T/{\epsilon }_0=1150$$

, d ₃₃ = 200 pCl / N, g ₃₃ = 19 pCl / N, K _p = 0.43 [1]. For these applications, the material is too high. $${\epsilon }_{33}^T/{\epsilon }_0$$

and low g ₃₃ .

, d₃₃=104 пКл/Н, K_p,=0.307, g₃₃≈11.9 мВм/Н, Q_m=273 [2]. Для указанных применений материал имеет низкие значения d₃₃, g₃₃, Кp и высокую Q_m.Known piezoelectric ceramic material based on niobates of sodium, potassium, lithium, including Na ₂ O, K ₂ O, Nb ₂ O ₅ , Ta ₂ O ₅ , Li ₂ O. The composition of the material corresponds to the chemical formula ((Na _0.5 K _0.5 ) _0.9 Li _0.1 ) Nb _0.8 Ta _0.2 O ₃ . Material has for best formulations. $${\epsilon }_{33}^T/{\epsilon }_0\approx 624$$

, d ₃₃ = 104 pC / N, K _p , = 0.307, g ₃₃ ≈11.9 mVm / N, Q _m = 273 [2]. For these applications, the material has low values of d ₃₃ , g ₃₃ , Kp and high Q _m .

, d₃₃=150 пКл/Н, g₃₃=24 пКл/Н, K_р=0.35, Q_м=80 [3]. Для указанных применений материал имеет низкие значения К_р, g₃₃ и недостаточно низкую $${\epsilon }_{33}^T/{\epsilon }_0$$

.Known piezoelectric ceramic material based on niobates of sodium, potassium, lithium, including Na ₂ O, K ₂ O, Li ₂ O, Ta ₂ O ₅ , Nb ₂ O ₅ . The composition of the material corresponds to the chemical formula [Li _0.055 (K _0.5 Na _0.5 ) _0.945 ] (Nb _0.99 Ta _0.01 ) O ₃ . Material has $${\epsilon }_{33}^T/{\epsilon }_0=700$$

, d ₃₃ = 150 pC / N, g ₃₃ = 24 pC / N, K _p = 0.35, Q _m = 80 [3]. For these applications, the material has low values of K _p , g ₃₃ and not low enough $${\epsilon }_{33}^T/{\epsilon }_0$$

.

, g₃₃≈29 мВм/Н, К_р=0.395 [4]. (Прототип) Для указанных применений материал имеет слишком высокую $${\epsilon }_{33}^T/{\epsilon }_0$$

и недостаточно высокие значения К_р.The closest in technical essence and the achieved result is a piezoelectric ceramic material based on niobates of sodium, potassium, lithium, including Na ₂ O, K ₂ O, Li ₂ O, Nb ₂ O ₅ , Ta ₂ O ₅ . The composition of the material corresponds to the chemical formula (Na _0.52 K _0.44 Li _0.04 ) Nb _0.8 Ta _0.2 O ₃ . Material has for best formulations. $${\epsilon }_{33}^T/{\epsilon }_0\approx 750$$

, g ₃₃ ≈29 mVm / N, K _p = 0.395 [4]. (Prototype) For these applications, the material is too high. $${\epsilon }_{33}^T/{\epsilon }_0$$

and not high enough To _p .

до значений ~ 600, при сохранении высоких значений g₃₃ (~ 30 мВм/Н) и низких значений Q_м (<150).The objective of the invention is to increase K _p (up to values ≥0.50), decrease $${\epsilon }_{33}^T/{\epsilon }_0$$

to values of ~ 600, while maintaining high g ₃₃ values (~ 30 mVm / N) and low Q _m values (<150).

These results are achieved in that the piezoelectric ceramic material based on sodium, potassium, lithium niobates, including Na ₂ O, K ₂ O, Li ₂ O, Nb ₂ O ₅ , Ta ₂ O ₅ , additionally contains Bi ₂ O ₃ , Fe ₂ O ₃ and Sb ₂ O ₅ in the following ratio of components, wt.%:

Na ₂ O 8.61-8.70 K ₂ O 11.15-11.26 Li ₂ O 0.49-0.50 Ta ₂ O ₅ 11.37-11.49 Nb ₂ O ₅ 61.59-62.19 Bi ₂ O ₃ 0.37-1.10 Fe ₂ O ₃ 0.13-0.38 Sb ₂ O ₅ 5.31-5.37

The composition of the material corresponds to the formula:

Li _a K _b Na _c Nb _d Ta _m Sb _n O ₃ + z (Bi ₂ O ₃ -Fe ₂ O ₃ ), where a = 0.04 (in mol.%), B = 0.4416 (in mol.%), C = 0.5184 (in mol.%), D = 0.864 (in mol.%), M = 0.096 (in mol.%), N = 0.04 (in mol.%), And + b + c = 1, d + m + n = 1, 0.005≤z≤0.015.

. Присутствие в материале Fe(II) с тетраэдрической координацией [6] (в отличие от Fe(III) - с октаэдрической координацией, свойственной всем перовскитным структурам, к которым относится и наш материал [7]), благоприятствует заполнению нерегулярных тетраэдрических позиций, существующих в ниобатных системах, что приводит к уплотнению материалов. Этому же способствует и образование жидких фаз [8], обусловленное низкой температурой плавления оксида Bi, облегчающих синтез объектов и упрочняющих керамический каркас за счет оказываемого ими цементирующего действия на кристаллиты. Все это также способствует повышению K_р.Combined modification of a material based on sodium, potassium, and lithium niobates with oxides containing, among other things, non-isovalent ions and ions with variable valency (Fe (II) and Fe (III)), leads to a complication of the structure of the material, in particular, due to amplification crystallochemical disorder due to the incorporation of modifier cations into both the regular A and B positions of the initial compound and the irregular tetrahedral sites existing in niobate systems [5] and the appearance of vacancies involved in operenose and diffusion processes. This helps to facilitate phase formation during the synthesis and sintering of ceramics, increase the manufacturability of objects and the formation, as a result, of a more perfect (less defective, homogeneous, more dense) structure, which leads to its tightening, that is, to an increase in K _p and a decrease $${\epsilon }_{33}^T/{\epsilon }_0$$

. The presence in the material of Fe (II) with tetrahedral coordination [6] (in contrast to Fe (III) with the octahedral coordination inherent in all perovskite structures, to which our material belongs [7]), favors the filling of irregular tetrahedral positions existing in niobate systems, which leads to compaction of materials. The formation of liquid phases also contributes to this [8], due to the low melting point of Bi oxide, which facilitate the synthesis of objects and strengthen the ceramic frame due to the cementing effect on crystallites. All this also contributes to an increase in K _p .

In addition, the high polarizability of Bi (III) increases the degree of deformation of the unit cells of the object, its anisotropy, and, as a consequence, spontaneous polarization, which also enhances the piezoelectric responses (in particular, K _p ) and piezoeanisatropy (d ₃₃ / | d ₃₁ |) .

1. An example of the manufacture of a piezoelectric ceramic material

The material was manufactured by conventional ceramic technology as follows. The initial reagents used were hydrocarbonates, carbonates and oxides of the following qualifications: NaHCO ₃ - “chda”, KHCO ₃ - “h”, Nb ₂ O ₅ - “NbO-PT”, Li ₂ CO ₃ - “hch”, Ta ₂ O ₅ - “TaO-1”, Sb ₂ O ₅ - “hch”, Fe ₂ O ₃ - “h”, Bi ₂ O ₃ - “h”. The synthesis was carried out by a single firing of mixtures of raw components: NaHCO ₃ , KHCO ₃ , Nb ₂ O ₅ , Li ₂ CO ₃ , Ta ₂ O ₅ , Sb ₂ O ₅ , Bi ₂ O ₃ , Fe ₂ O ₃ taken in quantities (mass. %, in the case of NaHCO ₃ , KHCO ₃ , Li ₂ CO ₃ in terms of the corresponding oxides): Na ₂ O = 8.70; K ₂ O = 11.26; Nb ₂ O ₅ = 62.19; Li ₂ O = 0.49; Ta ₂ O ₅ = 11.49; Sb ₂ O ₅ = 5.37, Bi ₂ O ₃ = 0.37, Fe ₂ O ₃ = 0.13 with intermediate grinding of the synthesized product. The synthesis was carried out in two stages at temperatures: T _synt. 1 = 1123 K, T _{synt. 2} 1143 K for τ _synt. 1 = τ _synt . ₂ = 6 hours. Sintering of samples in the form of columns ⌀12 mm, a height of 15-18 mm was carried out at T _SP. = 1473 K, the duration of the isothermal hold, τ h 2 = _ch. Metallization (applying electrodes) made by coating the flat surface of the pre-ground portion to a thickness of 1 mm samples silver-containing paste and its subsequent brazing at a temperature T _vzhig. = 1073 K for 0.5 h. Samples were polarized in a polyethylene siloxane liquid at a temperature of 410 K for 40 min in a constant electric field of 4 kV / cm.

2. An example of the manufacture of a piezoelectric ceramic material

The material was manufactured by conventional ceramic technology as follows. The initial reagents used were hydrocarbonates, carbonates and oxides of the following qualifications: NaHCO ₃ - “chda”, KHCO ₃ - “h”, Nb ₂ O ₅ - “NbO-PT”, Li ₂ CO ₃ - “hch”, Ta ₂ O ₅ - “TaO-1”, Sb ₂ O ₅ - “hch”, Fe ₂ O ₃ - “h”, Bi ₂ O ₃ - “h”. The synthesis was carried out by a single firing of mixtures of raw materials: NaHCO ₃ , KHCO ₃ , Nb ₂ O ₅ , Li ₂ CO ₃ , Ta ₂ O ₅ , Sb ₂ O ₅ , Bi ₂ O ₃ , Fe ₂ O ₃ taken in quantities (mass. %, in the case of NaHCO ₃ , KHCO ₃ , Li ₂ CO ₃ in terms of the corresponding oxides): Na ₂ O = 8.66; K ₂ O = 11.21; Nb ₂ O ₅ = 61.88; Li ₂ O = 0.49; Ta ₂ O ₅ = 11.43; Sb ₂ O ₅ = 5.34, Bi ₂ O ₃ = 0.74, Fe ₂ O ₃ = 0.25 with intermediate grinding of the synthesized product. The synthesis was carried out in two stages at temperatures T _synt. 1 = 1123 K, T _{synt. 2} 1143 K for τ _synt. 1 = τ _synt . ₂ = 6 hours. Sintering of samples in the form of columns ⌀12 mm, a height of 15-18 mm was carried out at T _SP. = 1473 K, the duration of isothermal exposure, τ _sp. = 2 hours. Metallization (deposition of electrodes) was carried out by applying onto a flat surface samples of silver-containing paste previously ground to a thickness of 1 mm and its subsequent firing at a temperature of T _firing. = 1070 K for 0.5 h. Samples were polarized in a polyethylene siloxane liquid at a temperature of 410 K for 40 min in a constant electric field of 4 kV / cm.

3. An example of the manufacture of a piezoelectric ceramic material

The material was manufactured by conventional ceramic technology as follows. The initial reagents used were hydrocarbonates, carbonates and oxides of the following qualifications: NaHCO ₃ - “chda”, KHCO ₃ - “h”, Nb ₂ O ₅ - “NbO-PT”, Li ₂ CO ₃ - “hch”, Ta ₂ O ₅ - “TaO-1”, Sb ₂ O ₅ - “hch”, Fe ₂ O ₃ - “h”, Bi ₂ O ₃ - “h”. The synthesis was carried out by a single firing of mixtures of raw components: NaHCO ₃ , KHCO ₃ , Nb ₂ O ₅ , Li ₂ CO ₃ , Ta ₂ O ₅ , Sb ₂ O ₅ , Bi ₂ O ₃ , Fe ₂ O ₃ taken in quantities (mass. %, in the case of NaHCO ₃ , KHCO ₃ , Li ₂ CO ₃ in terms of the corresponding oxides): Na ₂ O = 8.61; K ₂ O = 11.15; Nb ₂ O ₅ = 61.59; Li ₂ O = 0.49; Ta ₂ O ₅ = 11.37; Sb ₂ O ₅ = 5.31, Bi ₂ O ₃ = 1.10, Fe ₂ O ₃ = 0.38 with intermediate grinding of the synthesized product. The synthesis was carried out in two stages at temperatures: T _synt. 1 = 1123 K, T _{synt. 2} 1143 K for τ _synt. 1 = τ _synt . ₂ = 6 hours. Sintering of samples in the form of columns ⌀12 mm, a height of 15-18 mm was carried out at T _SP. = 1473 K, the duration of isothermal exposure, τ _sp. = 2 hours. Metallization (deposition of electrodes) was carried out by applying onto a flat surface samples of silver-containing paste previously ground to a thickness of 1 mm and its subsequent firing at a temperature of T _firing. = 1070 K for 0.5 h. Samples were polarized in a polyethylene siloxane liquid at a temperature of 410 K for 40 min in a constant electric field of 4 kV / cm.

(ε₀ - диэлектрическая постоянная), пьезомодули, |d₃₁| и d₃₃, коэффициент электромеханической связи планарной моды колебаний, К_р, механическая добротность, Q_m, скорость звука, $$V_1^E$$

. Пьезомодуль, d₃₃, определяли квазистатическим методом. Измерение экспериментальной плотности образцов, ρ_эксп, осуществляли методом гидростатического взвешивания в октане. Пьезочувствительность на толщинной моде колебаний, g₃₃, рассчитывали по формуле $$g_{33}=d_{33}/{\epsilon }_{33}^T$$

; удельную чувствительность - по формуле $${{\displaystyle d}}_{33}/\sqrt{{{\displaystyle \epsilon }}_{33}^T/{{\displaystyle \epsilon }}_0}$$

.Electrical characteristics were determined in accordance with OST 11.0444-87. The relative permittivity of polarized samples was measured, $${\epsilon }_{33}^T/{\epsilon }_0$$

(ε ₀ is the dielectric constant), piezoelectric modules, | d ₃₁ | and d ₃₃ , the electromechanical coupling coefficient of the planar vibrational mode, K _p , mechanical quality factor, Q _m , the speed of sound, $$V_{\mathrm{one}}^E$$

. The piezomodule, d ₃₃ , was determined by the quasistatic method. The experimental density of the samples, ρ _exp , was measured by hydrostatic weighing in octane. Piezosensitivity in the thickness mode of vibration, g ₃₃ , was calculated by the formula $$g_{33}=d_{33}/{\epsilon }_{33}^T$$

; specific sensitivity - according to the formula $${{\displaystyle d}}_{33}/\sqrt{{{\displaystyle \epsilon }}_{33}^T/{{\displaystyle \epsilon }}_0}$$

.

Table 1 shows the main characteristics of the material depending on the composition, and table 2 shows the main electrophysical characteristics of the optimal compositions of the proposed material.

The obtained experimental data (Table 1, examples 3-5) indicate that the piezoelectric ceramic material of the proposed composition has optimal, from the point of view of the technical problem to be solved, characteristics in the indicated range of component concentrations, beyond which leads to deterioration of parameters.

до значений ~600 при сохранении высокой g₃₃ ~30 мВ·м/Н и низкой Q_м<115.The data given in table 1-2, confirm the advantages of the proposed piezoelectric ceramic material compared with the material of the prototype, namely the increase of K _p to values of ~ 0.50, decrease $${\epsilon }_{33}^T/{\epsilon }_0$$

to values of ~ 600 while maintaining high g ₃₃ ~ 30 mV · m / N and low Q _m <115.

The effect of increasing K _{p is} achieved essentially by additional introduction into the material, including Na ₂ O, K ₂ O, Li ₂ O, Ta ₂ O ₅ , Nb ₂ O ₅ , oxides Sb ₂ O ₅ , Fe ₂ O ₃ and Bi ₂ O ₃ .

~600 предлагаемого пьезоэлектрического керамического материала определяет основное его назначение - использование в высокочастотных преобразователях, работающих в диапазоне частот 4.5-5.4 МГц. Это следует, прежде всего, из того, твердые растворы на основе ниобатов щелочных металлов (НЩМ) могут использоваться в качестве резонансных элементов пьезоэлектрических преобразователей в высокочастотных (ВЧ) (3.0-30.0) МГц и очень высокочастотных (ОВЧ) (30.0-300.0) МГц диапазонах. Классификация электромагнитных волн по частотным диапазонам представлена в [9]. При условии согласования преобразователя с нагрузкой (R_i=R_н) (обычно реализуемое в выпускаемой промышленностью радиоэлектронной аппаратуре выходное сопротивление R_н ~50 Ом для высоких частот), используя формулу для емкостного сопротивления преобразователя: R_i=1/ωС, где R_i - емкостное сопротивление преобразователя, Ом; ω - круговая частота, Гц; С - емкость, Ф; - можно приблизительно оценить интервалы значений емкости С=1/2πfR_i, для указанных диапазонов частот, а следовательно, и относительной диэлектрической проницаемости поляризованных элементов, $${\epsilon }_{33}^T/{\epsilon }_0=k\cdot C$$

, где k - коэффициент, зависящий от размеров элементов, ε₀=8.85·10^-12 Ф - диэлектрическая проницаемость вакуума; при k=1, $${\epsilon }_{33}^T/{\epsilon }_0=C$$

.Low relative permittivity $${\epsilon }_{33}^T/{\epsilon }_0$$

~ 600 of the proposed piezoelectric ceramic material determines its main purpose - use in high-frequency converters operating in the frequency range 4.5-5.4 MHz. This follows, first of all, from the fact that solid solutions based on alkali metal niobates (NLM) can be used as resonant elements of piezoelectric transducers in high-frequency (HF) (3.0-30.0) MHz and very high-frequency (VHF) (30.0-300.0) MHz ranges. Classification of electromagnetic waves by frequency ranges is presented in [9]. Provided that the converter is matched with the load (R _i = R _n ) (usually the output impedance R _n ~ 50 Ohm for high frequencies that is used in commercial electronic equipment), using the formula for the capacitance of the converter: R _i = 1 / ωС, where R _i - capacitance of the converter, Ohm; ω is the circular frequency, Hz; C is the capacity, f; - you can approximately estimate the intervals of the values of the capacitance C = 1 / 2πfR _i for the indicated frequency ranges, and therefore the relative permittivity of polarized elements, $${\epsilon }_{33}^T/{\epsilon }_0=k\cdot C$$

where k is a coefficient depending on the size of the elements, ε ₀ = 8.85 · 10 ^-12 F is the dielectric constant of the vacuum; for k = 1, $${\epsilon }_{33}^T/{\epsilon }_0=C$$

.

, реализуемые в объемных керамических образцах в ВЧ-диапазоне. Там же (∗) приведен комментарий к таблице. Таким образом, при частотах 4.55-5.31 МГц необходимы значения $${\epsilon }_{33}^T/{\epsilon }_0=600-700$$

для снижения сопротивления преобразователя, что улучшает его согласование с нагрузкой.Table 3 shows the relative permittivity, $${\epsilon }_{33}^T/{\epsilon }_0$$

realized in bulk ceramic samples in the high-frequency range. There (∗) is a comment on the table. Thus, at frequencies of 4.55-5.31 MHz, the required values $${\epsilon }_{33}^T/{\epsilon }_0=600-700$$

to reduce the resistance of the converter, which improves its coordination with the load.

~600 предлагаемого пьезоэлектрического керамического материала позволяет использовать его в высокочастотной технике, в частности в ультразвуковых пьезокерамических преобразователях, предназначенных для работы в воздушной среде в качестве излучателей и приемников в системах дистанционного управления, индикаторах близости препятствий, в устройствах для измерения скорости газового потока.High values of K _p ~ 0.50, g ₃₃ ~ 30 mV · m / N and low values of Q _m ~ 115 in combination with a low value of relative permittivity $${\epsilon }_{33}^T/{\epsilon }_0$$

~ 600 of the proposed piezoelectric ceramic material allows its use in high-frequency technology, in particular in ultrasonic piezoelectric transducers designed to operate in the air as emitters and receivers in remote control systems, proximity indicators of obstacles, and devices for measuring gas flow velocity.

Information sources

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Claims (1)

Piezoelectric ceramic material based on sodium, potassium, lithium niobate, including Na ₂ O, K ₂ O, Li ₂ O, Ta ₂ O ₅ , Nb ₂ O _5, characterized in that it additionally contains Bi ₂ O ₃ , Fe ₂ O ₃ and Sb ₂ O ₅ in the following ratio of components, wt.%:
Na ₂ O 8.61-8.70 K ₂ O 11.15-11.26 Li ₂ O 0.49-0.50 Ta ₂ O ₅ 11.37-11.49 Nb ₂ O ₃ 61.59-62.19 Bi ₂ O ₃ 0.37-1.10 Fe ₂ O ₃ 0.13-0.38 Sb ₂ O ₅ 5.31-5.37