RU2453518C2 - Piezoceramic material - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: piezoceramic material on the basis of a system of solid solutions (1-x)BiScO₃-xPbTiO₃ contains oxides of bismuth, scandium, lead, titanium and chrome at the following ratio of components, wt %: Bi₂O₃ 26.0-29.0; Sc₂O₃ 7.6-8.5; PbO 46.0-49.0; TiO₂ 16.5-17.5; Cr₂O₃ 0.05-0.30.

EFFECT: material is characterised by lower value of dielectric losses and quite low value of mechanical quality at high temperature of Curie point, high values of dielectric permeability and piezoelectric characteristics.

4 tbl

Description

The invention relates to the field of piezoelectric ceramic materials used for the manufacture of piezoelectric elements used in high-temperature vibrometry, as well as for the manufacture of piezoelectric elements of piezoelectric transducers of ultrasonic (ultrasonic) flaw detection and defectometry, ultrasonic medical diagnostic equipment, geophysical ultrasonic equipment and high-frequency sonar equipment .

Piezoceramic material for high vibrometry should possess high piezoelectric characteristics, relatively high dielectric constant, low dielectric losses (tgδ) in weak electrical fields and high temperature Curie point _(Tc) to be not less than 100 ° C above the temperature upper limit operating temperature range.

Piezoceramic material for ultrasound transducers used in ultrasonic flaw detection and other fields of science and technology listed above should, with sufficiently high dielectric and piezoelectric characteristics, additionally have a low mechanical quality factor, which allows for high resolution ultrasound equipment.

A known group of piezoelectric materials based on a system of solid solutions of lead zirconate-titanate (PZT) with sufficiently high dielectric and piezoelectric characteristics in the temperature range -60- + 250 ° C. This group of materials includes the widely used PZT-5A [1] and TsTS-26 [2]. The upper limit of the operating temperature range of these materials (+ 250 ° C) is limited by the temperatures of their Curie points, which for PZT-5A and TsTS-26 are 365 ° C and 350 ° C, respectively. The characteristics of these two and close to them in terms of properties and applicability of known piezoceramic materials are given in table 1. The main disadvantage of this group of piezoceramic materials is the relatively low temperature of the upper boundary of the operating temperature range.

Piezoelectric elements for flaw detection, defectometry and other ultrasound applications listed above are usually made of the same piezoceramic materials, the parameters of which are presented in Table 1. To increase the resolution of ultrasound equipment, it is necessary to use piezoceramic materials with a lower mechanical quality factor compared to the materials of Table 1. For this purpose, in some cases, piezoceramic materials based on lead methaniobate (PbNb ₂ O ₆ ) are used, the parameters of which are presented in Table 2. The main features of these materials are very low mechanical Q factor and at the same time their low main functional piezoelectric characteristics (k _t , d ₃₃ ). The latter significantly limits the possibilities of effective application of this group of piezoceramic materials. In addition, materials based on lead methaniobate are characterized by low reproducibility of parameters, they are very low-tech.

и Т_раб взяты из [3].The closest to the claimed piezoelectric ceramic material in terms of chemical composition and electrophysical characteristics are piezoceramic materials of a system of solid solutions of lead bismuth titanate scandate (1) BiSCO ₃ -xPbTiO ₃ , the compositions of which correspond to the region of tetragonal-rhombohedral morphotropic phase transition [3]. In [3], perovskite materials are patented for high-temperature actuators and converters, the composition of which corresponds to the general formula (1) ВiМеО ₃ -хРbТiO ₃ , where Me is the corresponding size cation or combination of cations, and x is in the range 0.50-0, 90. As Me in [3], the elements Sc are patented (with x = 0.62-0.66), In, Yb, lanthanides La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er , Tm, Lu, and actinides Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr. In [3], the following donor and acceptor additives (modifiers) are also patented: La, Fe, Mn, Nb, Sn, Ba, Na, K, Ni, Sr, and combinations thereof. The electrophysical characteristics of the four materials of the system (1) ViScO ₃ -xPbTiO ₃ are given in table 3, where all parameters except

and T _slave taken from [3].

Piezoceramic materials, the parameters of which are given in Table 3, have high piezoelectric properties (d ₃₃ , k _p ) and high dielectric constant, high T _k (higher than that of materials of the PZT system presented in Table 1) and significantly lower compared to with materials of the PZT system by mechanical quality factor. The main disadvantage of the materials of the system of (1) ВiSсО _3- хРbТiO ₃ is the high tanδ, which is significantly higher than that of the materials of the PZT system (Table 1), and it increases with increasing temperature and decreasing frequency at which measurements are performed. High tanδ and its growth with increasing temperature limit the possibility of using materials of the (1) ВiSсО _3- хРbТiO _{3 system} to create high-temperature vibration sensors, actuators, and other devices operating at temperatures above 250 ° C.

The problem to which this invention is directed, is to achieve a technical result, which consists in obtaining a piezoceramic material with high dielectric constant, high piezoelectric properties and high temperature of the Curie point with low dielectric loss and low mechanical quality factor.

The problem is solved by introducing into the materials of the system (1) BiScO ₃ -xPbiO ₃ (x = 0.63-0.66) in addition to stoichiometry of the acceptor additive Cr ₂ O ₃ in an amount of 0.05-0.30 wt.%.

The specified technical result is achieved in that the piezoceramic material containing oxides of bismuth, scandium, lead and titanium additionally contains chromium oxide in the following ratio of components, wt.%: Bi ₂ O ₃ 26.0-29.0; SC ₂ O ₃ 7.6-8.5; PbO 46.0-49.0; TiO ₂ 16.5-17.5; Cr ₂ O ₃ 0.05-0.30.

Thus, the hallmark of the invention is that the material further comprises chromium oxide in the following ratio of components, wt.%: Bi ₂ O ₃ 26,0-29,0; SC ₂ O ₃ 7.6-8.5; PbO 46.0-49.0; TiO ₂ 16.5-17.5; Cr ₂ O ₃ 0.05-0.30.

, пьезосвойствами (d₃₃>280·10^-12 Кл/Н) и температурой точки Кюри (Т_к>415°С) при низких диэлектрических потерях (tgδ<0,02) и низкой механической добротности

.The specified set of distinctive features allows you to achieve the named technical result, namely, that the piezoceramic material has a high dielectric constant

piezoelectric properties (d ₃₃ > 280 · 10 ^-12 C / N) and the temperature of the Curie point (Т _к > 415 ° С) at low dielectric losses (tgδ <0.02) and low mechanical quality factor

.

Production example: the material obtained by solid-phase synthesis, piezoelectric samples of the material obtained by sintering in air in a lead-containing filling.

Oxides Bi ₂ O ₃ (≥99.1%), Sc ₂ O ₃ (≥99.9%), PbO (≥99.1%), TiO ₂ (≥99.8%, anatase) were used as initial raw materials ), Cr ₂ O ₃ (≥99.8%). The initial raw materials in the form of powders were weighed on an analytical balance in accordance with their calculated concentrations and taking into account the content of the basic substance and mixed for 15 minutes in distilled water with grinding media made from stabilized zirconium dioxide. The resulting suspension of the mixture was dried at 120 ° C. The blends were briquetted and synthesized in high-alumina capsules at 800 ° С for 6 hours. The synthesized briquettes were crushed and ground in an aqueous medium in the same attritor for 15 minutes. The resulting suspensions of powders of piezoceramic materials were dried at 120 ° C to constant weight. The obtained powders were rubbed through a sieve with a mesh 0056, after which the values of the external specific surfaces of the obtained materials, whose values were in the range of (680-800) m ² / kg, were determined using the gas permeability method with the PSX-4 device. A bundle of 6 wt.% A five percent aqueous solution of polyvinyl alcohol was introduced into the powders of materials. Billets of standard piezoceramic samples were pressed with a pressure of 80-100 MPa in the form of cylinders ⌀14 × 12 mm. The billets were fired in a lead-containing filling in high-alumina capsules at temperatures of 1130 and 1150 ° C for 4 hours. Standard samples in the form of ⌀10 × 0.5 mm disks were made from fired billets. Silver-containing paste was applied to the disks, which was burned in a conveyor furnace at 800 ° C. The standard samples were polarized in a polyethylsiloxane liquid at 100-120 ° C with exposure to a constant electric field of 5 × 10 ⁶ V / m for 15 min. The parameters of standard samples were measured at 23 ± 5 ° С not earlier than 24 hours after polarization. Measurements and calculations of parameters were performed in accordance with the procedures [2].

и пьезоактивность (d₃₃, |d₃₁|, k_t, k_p), а его диэлектрические потери (tgδ) ниже по сравнению с прототипом (табл.1 и составы №1, 6, 11, 16 табл.4); механическая добротность

с увеличением концентрации Сr₂О₃ несколько возрастает по сравнению с

прототипа, но остается ниже чем у пьезокерамических материалов системы ЦТС (табл.1). По сравнению с пьезокерамическими материалами на основе РbNb₂О₆ (табл.2) предлагаемый материал имеет существенно более высокие диэлектрическую проницаемость и пьезоактивность. Поскольку введение Сr₂О₃ в пределах концентраций данного изобретения не приводит к снижению Т_к, но существенно снижает tgδ, предлагаемый материал является высокотемпературным пьезокерамическим материалом с верхней границей интервала рабочих температур +300°С. Выход за пределы концентраций Сr₂О₃ данного изобретения приводит либо к увеличению tgδ (составы №1, 7, 13, 19 табл.4), либо к увеличению

(№6, 12, 18, 24 табл.4).Table 4 shows the main electrophysical characteristics of the proposed material, depending on its chemical composition and the molar fraction of PbTiO ₃ solid solution (1) BiScO ₃ -xPbTiO ₃ . The data presented in table 4 indicate that the proposed material has optimal characteristics in the range of concentrations of the components specified in the claims (compositions No. 2-5, 7-10, 12-15 and 17-20). The material has a sufficiently high dielectric constant.

and piezoelectric activity (d ₃₃ , | d ₃₁ |, k _t , k _p ), and its dielectric loss (tgδ) is lower compared to the prototype (table 1 and compositions No. 1, 6, 11, 16 of table 4); mechanical quality factor

with an increase in the concentration of Cr ₂ O ₃ slightly increases compared with

prototype, but remains lower than that of piezoceramic materials of the PZT system (Table 1). Compared with piezoceramic materials based on PbNb ₂ O ₆ (table ₂ ), the proposed material has significantly higher dielectric constant and piezoelectric activity. Since the introduction of Cr ₂ O ₃ within the concentration range of this invention does not lead to a decrease in T _to , but significantly reduces tanδ, the proposed material is a high-temperature piezoceramic material with an upper boundary of the operating temperature range of + 300 ° C. Going beyond the concentration of Cr ₂ About _{3 of} this invention leads either to an increase in tanδ (compounds No. 1, 7, 13, 19 of Table 4), or to an increase

(No. 6, 12, 18, 24 table 4).

INFORMATION SOURCES

1. Electronic catalog of the Morgan company (USA, Great Britain): www.morganelectroceramics.com.

2. OST 11 0444-87. Piezoceramic materials. Technical conditions

3. US patent No. 6685849 (2004).

4. Sensor Technology Ltd. (BM Hi-Tech Division). Piezoelectric Ceramics. Product catalog. Application notes. 1995.

5. Electronic catalog of the company “ARS International Ltd.” (USA):

www.americanpiezo.com.

6. Electronic catalog of the company “Ferroperm” (Denmark):

http://www.ferroperm-piezo.com.

7. Electronic catalog of the company "Piezotechnologies" (USA):

www.PiezoTechnologies.com.

Claims (1)

Piezoceramic material, including oxides of bismuth, scandium, lead, titanium, characterized in that it additionally contains chromium oxide in the following ratio of components, wt.%: Bi ₂ O ₃ 26,0-29,0; SC ₂ O ₃ 7.6-8.5; PbO 46.0-49.0; TiO ₂ 16.5-17.5; Cr ₂ O ₃ 0.05-0.30.