RU2548278C1 - Piezoelectric ceramic material - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: piezoelectric ceramic material contains oxides of sodium, niobium, strontium, lithium, aluminium, bismuth and iron with the following component ratio, wt %: Na₂O 16.32-16.40, Nb₂O₅ 79.81-80.20, SrO 0.63, Li₂O 1.12-1.13, Al₂O₃ 0.40, Bi₂O₃ 0.92-1.28, Fe₂O₃ 0.32-0.44.

EFFECT: reduced value of the relative dielectric permeability and increased value of electromechanical connection coefficient of the planar mode of vibrations with the preservation of sufficiently high values of mechanical quality.

2 tbl

Description

The invention relates to piezoelectric ceramic materials based on sodium niobate and can be used to create high-frequency acoustoelectric transducers.

, (менее 200), достаточно высокие значения механической добротности, Q_m, (более 700), коэффициента электромеханической связи планарной моды колебаний, K_p, (более 0.15), пьезомодуля, d₃₃, (более 45 пКл/Н) и скорости звука, $$V_1^E$$

, (более 5.0 км/с).For these applications, the piezoelectric ceramic material should have a low relative permittivity, $${\epsilon }_{33}^T/{\epsilon }_0$$

, (less than 200), rather high values of mechanical Q factor, Q _m , (more than 700), electromechanical coupling coefficient of the planar oscillation mode, K _p , (more than 0.15), piezoelectric module, d ₃₃ , (more than 45 pC / N) and sound speed , $$V_{\mathrm{one}}^E$$

, (more than 5.0 km / s).

, d₃₃=97 пКл/Н, K_p=0.21, Q_m=319 [1].Known piezoelectric ceramic material based on sodium niobate, including carbonates Na ₂ CO ₃ , K ₂ CO ₃ , Li ₂ CO ₃ and oxides Nb ₂ O ₅ , Bi ₂ O ₃ , TiO ₂ , MnO, NdO, the composition of which corresponds to the chemical formula ( 1-x-y) Bi (Li _0.5 Me _0.5 ) O ₃ -xBaTiO ₃ -y (K _0.5 Bi _0.5 ) TiO ₃ -zM _a O _b , where Me = 0.9Nb + 0.1Mn, M = Nd, x = 0.06 , y = 0.89, z = 0.01. Material has for best formulations. $${\epsilon }_{33}^T/{\epsilon }_0=755$$

, d ₃₃ = 97 pC / N, K _p = 0.21, Q _m = 319 [1].

и недостаточно высокое значение Q_m. Кроме того, в состав материала входит редкоземельный элемент Nd, что значительно увеличивает себестоимость продукции.For these applications, the material is too large. $${\epsilon }_{33}^T/{\epsilon }_0$$

and not high enough value of Q _m . In addition, the rare earth element Nd is part of the material, which significantly increases the cost of production.

, K_p=0.389, Q_m=1408.2 [2].Known piezoelectric ceramic material based on sodium niobate, including the oxides K ₂ O, Na ₂ O, Nb ₂ O ₅ , CuO, the composition of which corresponds to the chemical formula 0.99K _0.5 Na _0.5 NbO ₃ -0.01CuO. Material has for best formulations. $${\epsilon }_{33}^T/{\epsilon }_0=237$$

, K _p = 0.389, Q _m = 1408.2 [2].

.For these applications, the material is not low enough $${\epsilon }_{33}^T/{\epsilon }_0$$

.

, K_p=0.143, Q_m=877 [3].Known is a piezoelectric ceramic material based on sodium niobate, including the oxides Na ₂ O, Nb ₂ O ₅ , SrO and carbonate Li ₂ CO ₃ , the composition of which corresponds to the chemical formula xNaNbO ₃ -yLiNbO ₃ -1-x-ySrNb ₂ O ₆ , where x = 0.85, y = 0.125. Material has for best formulations. $${\epsilon }_{33}^T/{\epsilon }_0=188$$

, K _p = 0.143, Q _m = 877 [3].

For these applications, the material has not high enough values of K _p . In addition, the material is manufactured using expensive hot-pressing technology, which is not applicable to industrial production conditions.

, K_p=0.12, Q_m=1000 [4] (Прототип).The closest to the claimed material in technical essence and the achieved result is a piezoelectric ceramic material based on sodium niobate, including the oxides K ₂ O, Na ₂ O, Nb ₂ O ₅ , CdO, the composition of which corresponds to the chemical formula (Na _x K _y Cd _z ) NbO ₃ , where x = 0.50-0.55, y = 0.20, z = 0.125-0.150. Material has for best formulations. $${\epsilon }_{33}^T/{\epsilon }_0=1360$$

, K _p = 0.12, Q _m = 1000 [4] (Prototype).

и недостаточно высокие значения K_p.For these applications, the material is too large. $${\epsilon }_{33}^T/{\epsilon }_0$$

and not high enough values of K _p .

; повышение коэффициента электромеханической связи планарной моды колебаний, K_p, (>0.15) при сохранении высокой механической добротности, Q_m, (>700). При этом материал должен быть получен по обычной керамической технологии, допускающей его массовое производство.The objective of the invention is to reduce the relative dielectric constant to $${\epsilon }_{33}^T/{\epsilon }_0=\mathrm{one\; hundred}-200$$

; an increase in the electromechanical coupling coefficient of the planar vibrational mode, K _p , (> 0.15) while maintaining high mechanical Q factor, Q _m , (> 700). In this case, the material must be obtained by conventional ceramic technology, allowing its mass production.

These results are achieved in that the piezoelectric ceramic material based on sodium niobate, including the oxides Na ₂ O and Nb ₂ O ₅ , according to the invention further comprises SrO, Li ₂ O, Al ₂ O ₃ , Bi ₂ O ₃ , Fe ₂ O ₃ when the following ratio of components (in wt.%):

Na ₂ O 16.32-16.40 Nb ₂ O ₅ 79.81-80.20 Sro 0.63-0.63 Li ₂ O 1.12-1.13 Al ₂ O ₃ 0.40-0.40 Bi ₂ O ₃ 0.92-1.28 Fe ₂ O ₃ 0.32-0.44

The composition of the material corresponds to the chemical formula:

[5]. Кроме того, гетеровалентное модифицирование оксидами Al₂O₃, Bi₂O₃ и особенно Fe₂O₃ (с ионом переменной валентности Fe(II), Fe(III)) приводит к росту числа кислородных вакансий, выступающих в качестве центров пининга доменных стенок, что затрудняет доменные переключения и, как следствие, благоприятствует повышению степени сегнетожесткости керамики, а следовательно, снижению $${\epsilon }_{33}^T/{\epsilon }_0$$

и повышению Q_m. Введение Bi₂O₃, способствуя образованию низкоплавких Bi-содержащих эвтектик, приводит к уплотнению структуры и повышению пьезоэлектрических параметров, в частности, K_p.Modification of the material based on sodium niobate with oxides of strontium, SrO, lithium, Li ₂ O, aluminum, Al ₂ O ₃ , bismuth, Bi ₂ O ₃ and iron, Fe ₂ O ₃ , leads to a complex effect. The introduction of Li ⁺ and Al ³⁺ ions, characterized by a low value of α / r ³ (where α is the polarizability, r is the ion radius), helps to reduce $${\epsilon }_{33}^T/{\epsilon }_0$$

[5]. In addition, heterovalent modification with oxides of Al ₂ O ₃ , Bi ₂ O _3, and especially Fe ₂ O ₃ (with Fe (II), Fe (III) ions of variable valency) leads to an increase in the number of oxygen vacancies acting as pinning centers for domain walls , which complicates domain switching and, as a result, favors an increase in the degree of ferro rigidity of ceramics, and, consequently, a decrease $${\epsilon }_{33}^T/{\epsilon }_0$$

and increasing Q _m . The introduction of Bi ₂ O ₃ , contributing to the formation of low-melting Bi-containing eutectics, leads to a densification of the structure and an increase in piezoelectric parameters, in particular, K _p .

Table 1 shows the values of the electrophysical parameters of the piezoelectric ceramic material depending on the composition.

Table 2 shows the comparative electrophysical parameters of the prototype and the optimal composition of the inventive 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”, SrO - “chda”, Nb ₂ O ₅ - “NbO-PT”, Li ₂ CO ₃ - “hch”, Al ₂ O ₃ - “chda”, Fe ₂ O ₃ - “h”, Bi ₂ O ₃ - “h”. The synthesis was carried out by double calcining mixtures of raw components: NaHCO ₃ , SrCO ₃ , Nb ₂ O ₅ , Li ₂ CO ₃ , Al ₂ O ₃ , Bi ₂ O ₃ , Fe ₂ O ₃ taken in quantities (wt.%, In the case of NaHCO ₃ , KHCO ₃ , Li ₂ CO ₃ in terms of the corresponding oxides): Na ₂ O = 16.32-16.40; SrO = 0.63; Nb ₂ O ₅ = 79.81-80.20; Li ₂ O = 1.12-1.13; Al ₂ O ₃ = 0.40; Bi ₂ O ₃ = 0.92-1.28, Fe ₂ O ₃ = 0.32-0.44 with intermediate grinding of the synthesized product. The firing temperature during synthesis, T _synt. = 1140 K, the duration of isothermal exposure, τ ₁ = τ ₂ = 6 hours. Sintering of samples in the form of columns ⌀12 mm, height 15-18 mm was carried out at τ _sp. = 1450 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. = 1070 K for 0.5 h. The samples were polarized in a polyethylene siloxane liquid at a temperature of 430 K for 60 min in a constant electric field of 8 kV / cm.

образцов, коэффициент электромеханической связи планарной моды колебаний (K_p), прямой пьезомодуль (d₃₃), механическую добротность (Q_m) и скорость звука $$\left(V_1^E\right)$$

.In accordance with OST 11.0444-87, the electrophysical characteristics were determined: relative permittivities of polarized $$\left({\epsilon }_{33}^T/{\epsilon }_0\right)$$

samples, the electromechanical coupling coefficient of the planar oscillation mode (K _p ), the direct piezoelectric module (d ₃₃ ), the mechanical quality factor (Q _m ) and the speed of sound $$\left(V_{\mathrm{one}}^E\right)$$

.

(135-160); повышенным коэффициентом электромеханической связи планарной моды колебаний K_p (0.15-0.18); при сохранении высоких значений механической добротности Q_m (730-750). Выход за пределы заявленных концентраций компонентов приводит к значительному снижению целевых параметров, в частности, K_p.The obtained experimental data (table 1, examples 2-4) indicate that the piezoelectric ceramic material of the proposed composition has a set of electrophysical parameters that meet the objective of the invention: reduced values of relative dielectric constant $${\epsilon }_{33}^T/{\epsilon }_0$$

(135-160); increased coefficient of electromechanical coupling of the planar oscillation mode K _p (0.15-0.18); while maintaining high values of mechanical quality factor Q _m (730-750). Going beyond the stated concentrations of the components leads to a significant reduction in target parameters, in particular, K _p .

до 155, повышение коэффициента электромеханической связи планарной моды колебаний, K_p, до 0.18 при сохранении высоких значений Q_m (744) (в лучшем составе - пример №3 из табл.1).The data given in table 2, confirm the advantages of the proposed piezoelectric ceramic material compared with the material of the prototype, namely the reduction $${\epsilon }_{33}^T/{\epsilon }_0$$

up to 155, increasing the coefficient of electromechanical coupling of the planar vibrational mode, K _p , to 0.18 while maintaining high values of Q _m (744) (in the best composition - example No. 3 from table 1).

и повышения K_p достигается, по существу, введением в материал, включающий Na₂O и Nb₂O₅, следующих оксидов: SrO, Li₂O, Al₂O₃, Bi₂O₃, Fe₂O₃.Drop effect $${\epsilon }_{33}^T/{\epsilon }_0$$

and increasing K _{p is} achieved essentially by introducing into the material including Na ₂ O and Nb ₂ O _{5 the} following oxides: SrO, Li ₂ O, Al ₂ O ₃ , Bi ₂ O ₃ , Fe ₂ O ₃ .

материала определяют основное его назначение - использование в высокочастотных акустоэлектрических преобразователях. При условии согласования преобразователя с нагрузкой (R_i=R_H) (обычно реализуемое в выпускаемой промышленностью радиоэлектронной аппаратуре выходное сопротивление R_H~ 50 Ом длит высоких частот), используя формулу для емкостного сопротивления преобразователя: R_i=1/ωС, где R_i - емкостное сопротивление преобразователя, Ом; ω - круговая частота, Гц; C - 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, $${\epsilon }_{33}^T/{\epsilon }_0=C$$

. Таким образом, снижение значения $${\epsilon }_{33}^T/{\epsilon }_0$$

позволяет эффективно использовать элементы на основе предлагаемого материала на частоте 20-30 МГц.High values of Q _m and K _p combined with low $${\epsilon }_{33}^T/{\epsilon }_0$$

material determine its main purpose - use in high-frequency acoustoelectric transducers. Provided the converter is matched to the load (R _i = R _H ) (the output impedance R _H ~ 50 Ohm for the high frequencies that is usually implemented 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, $${\epsilon }_{33}^T/{\epsilon }_0=C$$

. Thus decreasing the value $${\epsilon }_{33}^T/{\epsilon }_0$$

allows you to effectively use elements based on the proposed material at a frequency of 20-30 MHz.

предлагаемого материала позволяют упростить технологию изготовления элементов за счет увеличения их толщины при работе на высоких частотах, а также обеспечить хорошее согласование элементов с внешней цепью по электрическому сопротивлению.High values $$V_{\mathrm{one}}^E$$

The proposed material allows us to simplify the manufacturing technology of elements by increasing their thickness when working at high frequencies, as well as to ensure good coordination of elements with an external circuit in electrical resistance.

Information sources

1. CN 103172370 A, IPC C04B 35/475, C04B 35/468, C04B 35/622, publication date 06/26/2013.

2. EP 1032057 (A1), IPC H01L 41/187, publication date 08/30/2000.

3. Copyright certificate No. 687042 by application No. 2467273, IPC C04B 35/00, publication date 05/28/1979.

4. RU 2498960, IPC C04B 35/49, publication date 11/20/2013.

5. Reznichenko L. A., Kuznetsova E. M., Razumovskaya O. N., Shilkina L. A. Crystal-chemical modeling of ferroelectric materials with low dielectric constant // Zh. 2001. T.75. No. 5. S.53-56.

Table 1 The electrophysical parameters of the inventive piezoelectric ceramic material depending on the composition N p / p Composition, mass. % Electrophysical parameters Na ₂ O Sro Nb ₂ O ₅ Li ₂ O Al ₂ O ₃ Bi ₂ O ₃ Fe ₂ O ₃

$${\epsilon }_{33}^T/{\epsilon }_0$$

K _p d ^_33, pC / H Q _m $$V_{\mathrm{one}}^E*{10}^{-3}$$

m / s one 16.45 0.63 80.40 1.13 0.40 0.74 0.25 125 0.12 eighteen 650 5.28 2 16.40 0.63 80.20 1.13 0.40 0.92 0.32 135 0.16 38 730 5.32 3 16.36 0.63 80.00 1.13 0.40 1.10 0.38 155 0.18 47 744 5.59 four 16.32 0.63 79.81 1.12 0.40 1.28 0.44 160 0.15 25 750 6.00 5 16.28 0.63 79.61 1.12 0.40 1.46 0.50 165 0.08 fifteen 830 6.10

table 2 Comparative electrophysical parameters of the prototype and the optimal composition of the inventive piezoelectric ceramic material N p / p Material

$${\epsilon }_{33}^T/{\epsilon }_0$$

K _p Q _m d ₃₃ , pCl / N $$V_{\mathrm{one}}^E*{10}^{-3}$$

m / s one Prototype RU 2498960 1360 0.12 1000 - - 2 Composition No. 3 (from table 1) 155 0.18 744 47 5.59

Claims (1)

A piezoelectric ceramic material based on sodium niobate, including Na ₂ O and Nb ₂ O ₅ and the following oxides SrO, Li ₂ O, Al ₂ O ₃ , Bi ₂ O ₃ , Fe ₂ O _3, in the following ratio of components, wt.%:
Na ₂ O 16.32-16.40
Nb ₂ O ₅ 79.81-80.20
SrO 0.63-0.63
Li ₂ O 1.12-1.13
Al ₂ O ₃ 0.40-0.40
Bi ₂ O ₃ 0.92-1.28
Fe ₂ O ₃ 0.32-0.44