## 1 Introduction  
Ultraviolet (UV) radiation that reaches the earth and damages skin can be divided into three key wavelengths: (i) UVC (32-280 nm), (ii) UVB (280-320 nm) and (iii) UVA (320-400 nm). UVA radiation is a major culprit in photoaging and skin cancers. Moreover, UVB, which primarily reaches the top-most layer of skin, is thought to be responsible for acute photodamage, including sunburn and some non-melanoma skin cancers [1]. Therefore, protection against harmful UVA and UVB radiation is very important. [PERSON] [2] pointed out that sunscreens used for the protection of human skin against the harmful effects of solar radiation must contain UV-absorbing substances. Fine particles of various metal oxides, such ZnO and TiO\({}_{2}\), are extensively used as agents to attenuate (scatter and/or absorb) UV radiation, and have many attractive characteristics, such as a long history of topical use, broad spectrum absorption, high photostability and low irritancy [3]. However, an extensive literature search found that the use of ZnO-TiO\({}_{2}\) as a sunscreen for cosmetic applications has not been fully investigated. [PERSON] and [PERSON] [4] first established the basic phase diagram of the ZnO-TiO\({}_{2}\) system, and reported the temperature and composition ranges of stability for zinc metatitanate (ZnTiO\({}_{3}\)) and zinc orthotitanate (Zn\({}_{2}\)TiO\({}_{4}\)). Only Zn\({}_{2}\)Ti\({}_{3}\)O\({}_{8}\), ZnTiO\({}_{3}\) and Zn\({}_{2}\)TiO\({}_{4}\) have been confirmed to exist in ZnO-TiO\({}_{2}\) systems by previous researchers [4; 5; 6; 7]. The compound of Zn\({}_{2}\)Ti\({}_{3}\)O\({}_{8}\) has a cubic structure with a lattice constant of \(a_{\rm o}=0.8390(5)\) nm, and has been observed to be a low-temperature form of ZnTiO\({}_{3}\) that exists at temperatures below 820 \({}^{\circ}\)C [7]. ZnTiO\({}_{3}\) has a rhombohedral structure with lattice constants of \(a_{\rm o}=0.5078(2)\) and \(c_{\rm o}=1.3920(1)\) nm [5]. When heated between 965 and 1010 \({}^{\circ}\)C, ZnTiO\({}_{3}\) decomposes and forms Zn\({}_{2}\)TiO\({}_{4}\) and rutile TiO\({}_{2}\)[6]. The compound of Zn\({}_{2}\)TiO\({}_{4}\) has a face-centered cubic crystal structure with a lattice constant of \(a_{\rm o}=0.8460(2)\) nm [8]. Zinc titanates, such as ZnTiO\({}_{3}\) and Zn\({}_{2}\)TiO\({}_{4}\), are attractive as sorbents for removing sulfur from hot coal gasification products [9; 10], pigments [11], and gas sensors for ethanol, NO and CO [12]. Due to the recent progress of microwave applications in the area of mobile telephones and satellite communications, these substances can also be used as dielectric resonators and fitters [13; 14]. Furthermore, [PERSON] _et al_. [15; 16] also found that doped and undoped ZnTiO\({}_{3}\) have a V-type resistivity-temperature characteristic and possess typical positive thermal coefficient resistivity (PTCR) properties when above the transition point. However, the use of Zn\({}_{2}\)Ti\({}_{3}\)O\({}_{8}\) or ZnTiO\({}_{3}\) as UV-attenuating agents has not been reported. The chemistry and microstructure are important factors for applications of zinc titanate powders. Hence, various methods have been adopted for the preparation of ZnTiO\({}_{3}\) powders, including conventional solid state reaction [5] and sol-gel processes [16; 17]. In addition, Zn\({}_{2}\)TiO\({}_{4}\) powders have been obtained by solid-state reaction [8], and the ball mill method [18]. However, the solid-state reaction processes have some drawbacks, such as high reaction temperature, large particle size and limited degree of chemical homogeneity. On the other hand, [PERSON] _et al_. [19] pointed out that a single phase of Zn\({}_{2}\)Ti\({}_{3}\)O\({}_{8}\) is produced when zinc titanyl oxalate hydrate decomposes at 650 \({}^{\circ}\)C for severalhours. However, until now, no information is available on the synthesis and characterization of Zn\({}_{2}\)Ti\({}_{3}\)O\({}_{8}\) powders by a hydrothermal process without the addition of a dispersant agent.