PTCR heating ceramic without NTC effect before Curie temperature and preparation method thereof

Abstract

The invention belongs to the field of thermistors, and discloses PTCR (positive temperature coefficient) heating ceramic without NTC (negative temperature coefficient) effect before Curie temperature and a preparation method of the PTCR heating ceramic. The preparation method comprises the following steps: (1) preparing a main material containing a barium salt, a lead salt, a calcium salt and a titanium salt according to the stoichiometric ratio of cations in BaxPbyCazTiO3; then mixing the main material, a semiconducting agent and an AST auxiliary material, and carrying out wet ball milling to obtain powder slurry; wherein 0 lt; xlt; 1, 0lt; yt; Yt; 1, 0.05 < = z < = 0.10, 0.97 < = (x + y + z) lt; 1.08, and x + y + z is not equal to 1; and (2) adding an adhesive into the powder slurry, drying, sequentially granulating and tabletting, sintering in a sintering furnace to obtain a PTCR ceramic chip, and preparing an electrode on the ceramic chip to obtain the PTCR heating ceramic. Compared with a traditional AST system, the heating ceramic formula system has the advantages that no NTC effect exists below the Curie temperature Tc, the impact current is small, and the starting speed is high.

Description

Technical Field

[0001] This invention belongs to the field of electronic ceramic components, and more specifically, relates to a PTCR heating ceramic without NTC effect before Curie temperature and its preparation method. Background Technology

[0002] PTCR ceramics generally refer to thermistors with a positive temperature coefficient (PTCR). When heated to its Curie temperature, the resistance of PTCR ceramic materials changes dramatically. Furthermore, due to its advantages such as self-regulating temperature, self-heating, flameless operation, and safety, PTCR thermistors are widely used in the electronics industry, including temperature sensors and overcurrent protectors, especially in the thermal management systems of new energy electric vehicles.

[0003] With the increasing popularity of new energy electric vehicles and the expansion of people's activity range, electric vehicles need to meet the requirements of longer driving range and performance, which necessitates more effective battery thermal management. Therefore, PTCR thermistors are also moving towards wider temperature ranges, higher operating voltages, and greater power. However, PTCR thermistors exhibit a negative temperature coefficient of resistance (NTCR) effect before the Curie temperature (Tc). During the low-temperature cold start phase, PTCR thermistors have a high resistance value, making rapid start-up difficult. Simultaneously, after applying a high voltage for startup, as the temperature continues to rise, the resistance reaches its minimum value due to the NTC effect, generating a large inrush current and increasing the possibility of ceramic chip breakdown. Therefore, eliminating the NTC effect of PTCR thermistors below the Curie temperature (i.e., reducing the negative temperature coefficient before Tc to zero) while simultaneously improving withstand voltage performance has become a challenge currently facing new energy electric vehicles. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a PTCR heating ceramic without NTC effect before Curie temperature and its preparation method. The purpose is to optimize the formula by adding calcium salt in a non-stoichiometric form to achieve the advantages of no NTC effect below Curie temperature Tc, low inrush current, and fast start-up speed, thereby solving the technical problem of NTC effect of PTCR thermistors below Curie temperature in the prior art.

[0005] To achieve the above objectives, according to one aspect of the present invention, a PTCR heating ceramic without NTC effect before the Curie temperature and a method for preparing the same are provided, comprising the following steps: (1) According to Ba x Pby Ca z The stoichiometric ratio of cations in TiO3, and a main material containing barium salt, lead salt, calcium salt and titanium salt is configured; then the main material, a semiconductor conversion agent and an AST auxiliary material are mixed and wet ball milled to obtain a powder slurry; where 0 < x < 1, 0 < y < 1, 0.05 ≤ z ≤ 0.10, 0.97 ≤ (x + y + z) < 1.08, and x + y + z ≠ 1; (2) Add a binder to the powder slurry and dry it, granulate and press it in sequence, then put it into a sintering furnace for sintering to obtain a PTCR ceramic sheet, and then prepare electrodes on the PTCR ceramic sheet to obtain a PTCR heating ceramic.

[0006] Preferably, the AST auxiliary material is composed of aluminum oxide, silicon dioxide and titanium dioxide; for every mole of Ba x Pb y Ca z TiO3, the amount of substance of aluminum oxide added corresponding to it is a mol, 0 < a ≤ 2; for every mole of Ba x Pb y Ca z TiO3, the amount of substance of silicon dioxide added corresponding to it is b mol, 0 < b ≤ 4: for every mole of Ba x Pb y Ca z TiO3, the amount of substance of titanium dioxide added corresponding to it is c mol, 0 < c ≤ 3.

[0007] Preferably, the amount of substance of Ba element contained in the main material Mol Ba 、the amount of substance of Pb element salt contained Mol Pb 、the amount of substance of Ca element contained Mol Ca and the amount of substance of Ti element salt contained Mol Ti satisfy the following relational expression: Mol Ba : Mol Pb : Mol Ca : Mol Ti = (0.6~0.8):(0.1~0.3):(0.05~0.10):1.

[0008] Preferably, the calcium salt is calcium carbonate or calcium nitrate, the barium salt is barium carbonate or barium nitrate, the lead salt is lead tetroxide or lead oxide, and the titanium salt is titanium dioxide.

[0009] Preferably, the semiconductor conversion agent is niobium pentoxide, lanthanum oxide, yttrium oxide or antimony trioxide.

[0010] Preferably, for every mole of Ba x Pb y Caz The amount of the substance of TiO3 added corresponding to the semiconductive agent is n mol, where 0.02 < n ≤ 0.50.

[0011] Preferably, in step (1), other additives are further added during the raw material mixing. The other additives include Mn(NO3)2, Li2CO3, and BN. For each mole of Ba x Pb y Ca z The amount of the substance of TiO3 added corresponding to the Mn(NO3)2 is m mol, where 0 < m ≤ 0.06. For each mole of Ba x Pb y Ca z The amount of the substance of TiO3 added corresponding to the Li2CO3 is 0.005 - 0.05 mol, and for each mole of Ba x Pb y Ca z The amount of the substance of TiO3 added corresponding to BN is q mol, where 0 < q ≤ 0.05.

[0012] Preferably, in step (1), the ball milling is performed in an alternating forward and reverse rotation mode. The switching interval time of the alternating forward and reverse rotation does not exceed 0.5 min, the rotation speed is 300 - 400 r / min, and zirconium balls are used for ball milling for 4 - 6 h; where the mass ratio of the total mass of all the mixed powders: zirconium balls: deionized water is 1:2:2.

[0013] Preferably, the binder is polyvinyl alcohol or polyvinyl butyral; when an aqueous solution of polyvinyl alcohol with a concentration of 5 - 15 wt% is used as the binder, the dosage is 5 - 12 wt% of the mass of all the mixed powders added.

[0014] According to another aspect of the present invention, there is provided a PTCR heating ceramic without NTC effect before the Curie temperature prepared by the preparation method according to any one of the above. It is characterized in that it takes lead barium titanate with a perovskite structure as the matrix, and there are microregions rich in non-ferroelectric calcium titanate inside the matrix.

[0015] Generally speaking, compared with the prior art by the above technical solutions conceived by the present invention, the following technical advantages are mainly possessed: In the present invention, according to the stoichiometric ratio of cations in Ba x Pb y Ca z TiO3, where 0 < x < 1, 0 < y < 1, 0.05 ≤ z ≤ 0.10, 0.97 ≤ (x + y + z) < 1.08, and a calcium salt is added in a non-stoichiometric ratio to achieve no NTC effect below the Curie temperature Tc. During high-temperature sintering, the incorporation of the Ca element makes Ca 2+Diffusion into the BaTiO3 lattice increases solid solubility, forming non-ferroelectric CaTiO3, which is enriched at the grain boundary surface. When it dissolves with ferroelectric BaTiO3, the phase transition diffusion becomes more pronounced with increasing non-ferroelectric content (i.e., z gradually increases in the range of 0.05–0.10), the ferroelectricity of the system relatively weakens, the Curie temperature range widens, the grain boundary barrier height increases, the temperature coefficient before the Curie temperature Tc gradually approaches zero, and the resistance-temperature characteristic curve becomes flatter, thus weakening the NTC effect before Tc. Furthermore, Ca has a grain-refining effect; the incorporation of an appropriate amount of Ca can improve the uniformity of grain morphology, making the grain size more uniform, significantly increasing the grain boundary ratio, enhancing carrier scattering, and reducing carrier concentration. The semiconductor characteristics exhibited by the PTCR heating ceramic before Tc are weakened, the temperature coefficient gradually approaches zero, and the NTC effect before the Curie temperature Tc is weakened. Simultaneously, the density of the PTCR heating ceramic is improved, accompanied by an increase in the pressure resistance of the PTCR ceramic sheet.

[0016] When the PTCR ceramic sheet of this invention is applied to thermistors in battery heating or air conditioning heating systems in thermal management systems, the temperature coefficient before the Curie temperature Tc is zero, which is considered as the elimination of the NTC effect before Tc. This significantly reduces the inrush current generated during the startup of the PTCR heating ceramic, improving the reliability of the ceramic sheet. Simultaneously, it enhances the startup speed of the PTCR heating ceramic at low temperatures, significantly improving its working efficiency. The elimination of the NTC effect before Tc means that the inrush current can be directly calculated using room temperature resistance, facilitating industrial use, especially in battery heating or air conditioning heating systems in the thermal management systems of new energy vehicles. This is of great significance for solving problems such as low-temperature cold starts in new energy electric vehicles. Attached Figure Description

[0017] Figure 1 These are the temperature resistance characteristic curves of CAST-PTCR in Example 1 of the present invention and conventional PTCR in Comparative Example 1.

[0018] Figure 2 These are the temperature resistance characteristic curves of PTCRs prepared with different calcium salt content formulations in Examples 2-4 of this invention.

[0019] Figure 3 This is the It characteristic curve of CAST-PTCR at 260V for Embodiment 1 of the present invention.

[0020] Figure 4 This is the It characteristic curve of a conventional PTCR at 260V, as shown in Comparative Example 1 of this invention. Detailed Implementation

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] The preparation method of the PTCR heating ceramic without NTC effect before the Curie temperature provided by the present invention specifically includes the following steps: (1) Prepare the main materials including barium salt, lead salt, calcium salt and titanium salt according to the stoichiometric ratio of cations in Ba x Pb y Ca z TiO3, mix the main materials, a semiconduction agent and an AST auxiliary material and perform wet ball milling to obtain a powder slurry; wherein, 0 < x < 1, 0 < y < 1, 0.05 ≤ z ≤ 0.10, 0.97 ≤ (x + y + z) < 1.08, and x + y + z ≠ 1; (2) Add a binder to the powder slurry, dry, granulate, press into tablets, and then put them into a sintering furnace for sintering to obtain PTCR ceramics, and then prepare electrodes on the PTCR ceramic sheets to obtain PTCR heating ceramics.

[0023] In the present invention, the AST auxiliary agent is an existing auxiliary agent composed of aluminum oxide, silicon dioxide and titanium dioxide. Preferably, the amounts of substances of aluminum oxide, silicon dioxide and titanium dioxide added per mole of Ba x Pb y Ca z TiO3 are a mol, 0 < a ≤ 2, b mol, 0 < b ≤ 4, c mol, 0 < c ≤ 3 respectively. That is, adding an AST auxiliary material and a calcium salt to the PTCR formula system forms the CAST-PTCR formula system described in the present invention.

[0024] Preferably, the semiconduction agent is niobium pentoxide, lanthanum oxide, yttrium oxide or antimony trioxide. The amount of substance of the semiconduction agent added per mole of Ba x Pb y Ca z TiO3 is n mol, and the value range of n is 0.02 < n ≤ 0.50.

[0025] Preferably, other auxiliary agents are also added during the raw material preparation. The other auxiliary agents include Mn(NO3)2, Li2CO3 and BN; the amounts of substances of Mn(NO3)2, Li2CO3 and BN added per mole of Ba x Pb y Ca zThe amounts of Mn(NO3)2, Li2CO3, and BN added to TiO3 are respectively mmol, 0<m≤0.06, 0.005~0.05mol, and q mol, 0<q≤0.05.

[0026] Preferably, a PTCR heating ceramic using a CAST formulation includes a main ingredient, a semiconductor agent, an AST additive, and other additives; the main ingredient includes BaTiO3, PbTiO3, and CaCO3. 3， Other additives include Mn(NO3)2, Li2CO3, and BN, while the semiconductor agent is Nb2O5.

[0027] In this invention, in step (1), the ball milling adopts an alternating forward and reverse rotation mode, with the interval between the forward and reverse rotation switching time not exceeding 0.5 min, the rotation speed being 300-400 r / min, and zirconium ball milling being used for 4-6 h; wherein the total mass ratio of powder to zirconium balls to deionized water is 1:2:2. In this invention, the ball-milled slurry is dried at a temperature between 85°C and 110°C. After the surface moisture of the slurry is dried, a polyvinyl alcohol aqueous solution with a total mass of 5-12 wt% and a concentration of 5-15 wt% is added as a binder, and stirring is continued until the powder is completely dry. In this invention, after the powder is completely dried, a granulation and tableting process is performed: the powder is ground until it is in granular form, and after sieving, a powder with excellent flowability is obtained to prepare ceramic blanks; wherein, the blank forming pressure is between 10 and 15 MPa. A 40-mesh sieve is used for sieving the powder.

[0028] In this invention, the pressed green blank is placed in an air atmosphere at 1200–1330°C to fully sinter it into ceramic; the surface of the ceramic is polished, and aluminum electrodes are printed on the ceramic surface. After firing, a sample is obtained. The electrode sintering temperature is 600–680°C, and the holding time is 10–30 minutes.

[0029] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] Example 1 A PTCR heating ceramic using a CAST formulation is prepared through the following steps: a. Ingredients: According to 1 mol Ba x Pb y Ca z The TiO3 ratio is adjusted as follows: Barium carbonate and titanium dioxide were synthesized by solid-state synthesis to obtain BaTiO3 powder with an equistoichiometric ratio of Ba and Ti, and lead tetroxide and titanium dioxide were synthesized by solid-state synthesis to obtain PbTiO3 powder with an equistoichiometric ratio of Pb and Ti.

[0031] Then, 183.749g BaTiO3 powder (x=0.77), 60.908g PbTiO3 powder (y=0.20), 8.001g CaCO3 powder (z=0.08), and 0.167g Nb2O5 powder (per mole of Ba) were added. x Pb y Ca z TiO3 added 0.21mol), AST additive, 0.048g Li2CO3 powder (per mole of Ba x Pb y Ca z 0.065 mol of TiO3 and 0.037 g of BN powder (per mole of Ba) x Pb y Ca z TiO3 (0.15 mol) and 0.036 g Mn(NO3)2 powder (per mole of Ba) x Pb y Ca z TiO3 (0.020 mol) was added and mixed. The AST additive contained 1.060 g Al2O3 (per mole of Ba). x Pb y Ca z 1 mol of TiO3 was added), and 1.201 g of SiO2 was added (per mole of Ba). x Pb y Ca z 2 mol of TiO3 and 0.498 g of TiO2 (per mole of Ba) were added. x Pb y Ca z 1 mol of TiO3 was added.

[0032] b. Place the above-mentioned mixed raw materials in a ball mill jar. At the same time, add zirconium dioxide grinding balls, and use an alternating forward and reverse rotation mode with a rotation interval of 0.5 min, a rotation speed of 400 r / min, and ball mill for 4 h. The mass ratio of raw materials, zirconium balls, and deionized water is 1:2:2.

[0033] c. Add 10 wt% of the mixed powder and a 10 wt% polyvinyl alcohol aqueous solution to the ball-milled slurry, stir, and then dry at 95°C until the powder is completely dry.

[0034] d. After the powder is completely dried, the granulation and tableting process is carried out: the powder is ground until it is in granular form, and then sieved using a 40-mesh sieve. After sieving, powder with excellent flowability can be obtained to prepare ceramic blanks; the blank forming pressure is 10MPa.

[0035] e. The pressed green blank is placed in an air atmosphere at 1262°C to fully sinter it into ceramic. The surface of the ceramic is polished and aluminum electrodes are printed on the ceramic surface. After firing at 650°C, a sample is obtained.

[0036] f. The prepared PTCR ceramic sample, i.e., CAST-PTCR.

[0037] Comparative Example 1 A PTCR heating ceramic using the AST formulation is prepared in the same way as in Example 1, except that CaCO3 powder is not added during the batching stage, resulting in a conventional PTCR.

[0038] Example 2 A PTCR heating ceramic using the CAST formula is prepared in the same way as in Example 1, except that 5.006g of CaCO3 powder (z=0.05) is added during the batching stage.

[0039] Example 3 A PTCR heating ceramic using the CAST formula is prepared in the same way as in Example 1, except that 7.006g of CaCO3 powder (z=0.07) is added during the batching stage.

[0040] Example 4 A PTCR heating ceramic using the CAST formula is prepared in the same way as in Example 1, except that 10.009g of CaCO3 powder (z=0.10) is added during the batching stage.

[0041] Comparative Example 2 A PTCR heating ceramic using the CAST formula is prepared in the same way as in Example 1, except that 3.003 CaCO3 powder (z=0.03) is added during the batching stage.

[0042] Comparative Example 3 A PTCR heating ceramic using the CAST formula is prepared in the same way as in Example 1, except that 4.004g of CaCO3 powder (z=0.04) is added during the batching stage.

[0043] The ceramic samples prepared above were tested using a ZWX-B R / T characteristic tester (refer to the test scheme described in detail in CN201920304979.X) to measure their resistance-temperature characteristics, PTCR current-voltage characteristics, and PTCR current-time characteristics, as well as their VI and It characteristics, using a PTCR current-time test system.

[0044] like Figure 1 As shown, the temperature resistance characteristics of the ceramic sample prepared in Example 1 were tested using a ZWX-B R / T characteristic tester (patent number). The results show that the temperature resistance characteristic curve of the ceramic sample prepared in Example 1 is significantly different from that of the ceramic sample prepared in Comparative Example 1 at T... C The curve is flatter. The ceramic sample prepared in Example 1 has a resistance (R25) of 4991.10 Ω at room temperature, an R25 / Rmin ratio of 0.923, and a resistance-to-weight ratio of 4.193. R25 / Rmin was used to evaluate the intensity of the NTC effect. The ceramic sample prepared in Example 1 has an R25 / Rmin ratio of 0.923 < 1, which eliminates the NTC effect below Tc in the PTC ceramic sample. Simultaneously, the resistance-to-weight ratio reaches 4.193, indicating faster heating in application. The breakdown voltage of the ceramic sample prepared in Example 1 was 892.69 V obtained through VI characteristic testing. The above experiments show that the PTC heating ceramic prepared by this formula has no NTC effect in the low-temperature region, and its electrical characteristics are suitable for use in the thermal management system of new energy electric vehicles.

[0045] like Figure 2As shown, the resistance-temperature characteristics of the ceramic samples prepared in Examples 2, 3, and 4 were tested using a ZWX-B R / T characteristic tester. The results show that the resistance-temperature characteristic curves of the ceramic samples prepared in Examples 2, 3, and 4 are flatter before TC compared to those of the ceramic samples prepared in Comparative Examples 2 and 3. The resistance (R25) of the ceramic samples prepared in Examples 2, 3, and 4 at room temperature are 111.8 Ω, 875.0 Ω, and 229.5 KΩ, respectively; the R25 / Rmin ratios are 1.974, 1.186, and 1.111, respectively; and the resistance-to-resistance ratios are 3.964, 3.430, and 2.436, respectively. The resistance of the ceramic samples prepared in Comparative Examples 2 and 3 at room temperature are 19.56 Ω and 32.85 Ω, respectively; the R25 / Rmin ratios are 2.773 and 3.004, respectively; and the resistance-to-resistance ratios are 4.638 and 4.483, respectively. Compared with Comparative Examples 2 and 3, the R25 / Rmin ratios of the ceramic samples prepared in Examples 2, 3, and 4 are closer to 1, indicating a weakened NTC effect. Furthermore, the breakdown voltages of the ceramic samples prepared in Examples 2, 3, and 4, obtained through VI characteristic testing, were 727.18V, 774.53V, and 693.45V, respectively, while the breakdown voltages of Comparative Examples 2 and 3 were 527.83V and 633.40V. In summary, the PTC heating ceramic prepared using the CAST formula described in this invention exhibits no NTC effect in the low-temperature region, and its electrical properties are also suitable for use in the thermal management systems of new energy electric vehicles.

[0046] The It characteristic parameters of the ceramic samples from Example 1 and Comparative Example 1 were selected at an applied voltage of 260V. For example... Figure 3 As shown, the ceramic sample of Example 1 had a start-up time of 48 ms and an impact current / initial current ratio of 1. Figure 4 As shown, the ceramic sample of Comparative Example 1 had a start-up time of 188 ms and an inrush current / initial current ratio of 2.25. The PTCR ceramic sample prepared using the formulation of this invention exhibits no NTC effect below Tc, has an inrush current / initial current ratio of 1, a small inrush current during start-up, a low change in voltage after start-up, and a fast start-up speed, greatly meeting the requirements of heating systems for new energy electric vehicles. In contrast, the resistors prepared in Comparative Example 1 exhibit a strong NTC effect below Tc, resulting in a large inrush current and requiring auxiliary control devices to assist in start-up, leading to a longer start-up time.

[0047] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of protection of this invention and its equivalents, this invention also intends to include these modifications and variations. The above-described embodiments are merely preferred embodiments given to fully illustrate this invention, and their scope of protection is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on this invention are all within the scope of protection of this invention.

Claims

1. A method for producing a PTCR heating ceramic having no NTC effect before the Curie temperature, characterized in that, It comprises the following steps: (1) According to Ba x Pb y Ca z TiO3 stoichiometric ratio of cations, configuration contains barium salt, lead salt, calcium salt and titanium salt main material; then the main material, semi-conducting agent and AST auxiliary material are mixed and wet ball milled to obtain a powder slurry; wherein 0 < x < 1, 0 < y < 1, 0.05 ≤ z ≤ 0.10, 0.97 ≤ (x+y+z) < 1.08, and x+y+z≠1; (2) adding a binder to the powder slurry, drying, granulating and tabletting in sequence, and then sintering in a sintering furnace to obtain PTCR ceramic sheets, and then preparing electrodes on the PTCR ceramic sheets to obtain PTCR heating ceramics.

2. The method for preparing PTCR-heated ceramics without NTC effect before the Curie temperature as described in claim 1, characterized in that, The AST auxiliary material is composed of aluminum oxide, silicon dioxide and titanium dioxide; the amount of substance of Ba x Pb y Ca z TiO3 added corresponds to the amount of substance of the aluminum oxide a mol, 0 x Pb y Ca z TiO3 added corresponds to the amount of substance of the silicon dioxide b mol, 0 x Pb y Ca z TiO3 added corresponds to the amount of substance of the titanium dioxide c mol, 0 3. The method of claim 1, wherein the Curie temperature PTC heating ceramic having no NTC effect before the Curie temperature is prepared by the steps of: preparing a mixture of a first material having a Curie temperature and a second material having a Curie temperature lower than the first material; and sintering the mixture. Mol of Ba element contained in the main material Ba Mol of Pb element salt contained Pb Mol of Ca element contained Ca Mol of Ti element salt contained Ti Mol of Ba element contained Ba Mol of Pb element contained Pb Mol of Ca element contained Ca Mol of Ti element contained Ti = (0.6-0.8) : (0.1-0.3) : (0.05-0.10) :

1.

4. The method for preparing PTCR-heated ceramics without NTC effect before the Curie temperature as described in claim 1, characterized in that, The calcium salt is calcium carbonate or calcium nitrate, the barium salt is barium carbonate or barium nitrate, the lead salt is lead trioxide or lead oxide, and the titanium salt is titanium dioxide.

5. The method for preparing PTCR-heated ceramics without NTC effect before the Curie temperature as described in claim 1, characterized in that, The semi-conducting agent is niobium pentoxide, lanthanum oxide, yttrium oxide or antimony trioxide.

6. The method of claim 1, wherein the Curie temperature PTC heating ceramic having no NTC effect before the Curie temperature is prepared by the steps of: preparing a mixture of a first material and a second material; and sintering the mixture to form the Curie temperature PTC heating ceramic having no NTC effect before the Curie temperature. Ba x Pb y Ca z TiO3addition corresponds to a quantity of substance n mol of the substance corresponding to the semiconducting agent, 0.02 < n < 0.

50.

7. The method for preparing PTCR-heated ceramics without NTC effect before the Curie temperature as described in claim 1, characterized in that, In step (1), other additives are also added at the time of mixing the raw materials, said other additives including Mn(NO3)2, Li2CO3 and BN, 0 < m ≤ 0.06 mol of substance corresponding to said Mn(NO3)2 per mole of Ba x Pb y Ca z TiO3, 0.005 to 0.05 mol of substance corresponding to said Li2CO3 per mole of Ba x Pb y Ca z TiO3, 0.005 to 0.05 mol of substance corresponding to said Li2CO3 per mole of Ba x Pb y Ca z TiO3, 0.005 to 0.05 mol of substance corresponding to said Li2CO3 per mole of Ba 8. The method for preparing PTCR-heated ceramics without NTC effect before Curie temperature as described in claim 1, characterized in that, In step (1), the ball milling is performed in a forward-reverse alternating rotation mode, the switching interval of the forward-reverse alternating rotation is not more than 0.5 min, the rotation speed is 300-400 r / min, and the zirconium ball milling is performed for 4-6 h; wherein the mass ratio of the total mass of the mixed powders, the zirconium ball and the deionized water is 1:2:

2.

9. The method for preparing PTCR-heated ceramics without NTC effect before the Curie temperature as described in claim 1, characterized in that, The binder is polyvinyl alcohol or polyvinyl butyral; when the polyvinyl alcohol aqueous solution with a concentration of 5-15 wt% is used as the binder, the amount used is 5-12 wt% of the mass of the mixed powders.

10. A PTCR heating ceramic without NTC effect before Curie temperature, obtainable by the process according to any one of claims 1 to 9, characterized in that, The perovskite structure lead barium titanate is used as the matrix, and there are micro-zones rich in non-ferroelectric calcium titanate in the matrix.

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